gis

The NCGIA Core Curriculum in GIScience

Last update - August 13, 2000

About the GISCC

Legend

(001) - Numbers in brackets indicate each unit's unique key number. Italicized names indicate unit authors. GC notes links to related materials in the Geographer's Craft. old CC links to the on-line version of the original Core Curriculum. CCTP refers to the Core Curriculum for Technical Programs bulleted items in Arial font are additional, suggested unit topics

0. What is GIS? (002), Michael Goodchild

1. Fundamental Geographic Concepts for GIScience (004)

1.1. The World in Spatial Terms (005), ed. Reg Golledge1.1.1. Human Cognition of the Spatial World (006), Dan Montello 1.1.2. Asking Geographic Questions (007), Tim Nyerges and Reg Golledge

1.2. Representing the earth digitally (008)

o features, pictures, variables; points, lines, areas, fields, 3D; processes and time

1.3. Position on the earth (012), ed. Ken Foote1.3.1. Coordinate Systems Overview (013), Peter Dana 1.3.2. Latitude and Longitude (014), Anthony Kirvan 1.3.3. The Shape of the Earth (015), Peter Dana 1.3.4. Discrete Georeferencing (016), David Cowen 1.3.5. Global Positioning Systems Overview (017), Peter Dana

1.4. Mapping the earth (018)

1.4.1. Projections and transformations (019), **from the old CC, see also GC notes 1.4.2. Maps as Representations of the World (020), Judy Olson

1.5. Spatial relationships (021)

o connections and topology; networks; distance and direction; flow and diffusion; spatial hierarchies; boundaries; spatial patterns; attributes of relationships

1.6. Abstraction and incompleteness (030)1.6.1. Sampling the World (031), **from the old CC1.6.2. Line Generalization (034), **from the old CC

o scale and geographic detail; uncertainty; generalization

2. Implementing Geographic Concepts in GISystems (035)2.1. Defining characteristics of computing technology (036)

2.1.1. Fundamentals of Data Storage - Carol Jacobson (037) 2.1.2. Algorithms (040)

2.1.2.1. Simple Algorithms for GIS I: Intersection of Lines (184), **from theold CC 2.1.2.2. Simple Algorithms for GIS II: Operations on Polygons, (185) **from the old CC 2.1.2.3. The Polygon Overlay Operation (186), **from the old CC

o data versus processes; history; object orientation

2.2. Fundamentals of computing systems (042)

o operating systems; programming languages and software engineering; developing algorithms; user interfaces; computer networks; hardware for GISystems

2.3. Fundamentals of information science (050)2.3.1. Information Organization and Data Structure (051), Albert Yeung 2.3.2. Non-spatial Database Models (045), Thomas Meyer

o data modeling

2.4. Representing fields (054), Michael Goodchild2.4.1. Rasters (055), Michael Goodchild 2.4.2. TINs (056), **from the old CC 2.4.3. Quadtrees and Scan Orders (057), Michael Goodchild

o polygon coverages

2.5. Representing discrete objects (059)

o storing relationships; computing relationships; topology for geodata; object hierarchies

2.6. Representing networks (064), Benjamin Zhan 2.7. Representing time and storing temporal data (065) 2.8. Populating the GISystem (066) - see the GC notes and the CCTP

o creating digital data - sampling the world; remote sensing; GPS as a data source; digitizing and scanning; editing

o accessing existing data - data exchange; open GIS; finding data; data conversion; transfer standards; distributed networked databases; generating data from existing data

o metadata

2.9. Kinds of geospatial data (082)2.9.1. Transportation Networks (183), Val Noronha 2.9.2. Natural Resources Data (090), Peter Schut

2.9.2.1. Soil Data for GIS (091), Peter Schut

hydrography; land cover and vegetation; geology; climate; terrain

2.9.3. Land Records - see Unit 164

o administrative boundary data; demographic and health data; global data

2.10. Handling uncertainty (096), ed. Gary Hunter (see also GC notes)2.10.1. Managing Uncertainty in GIS (187), Gary Hunter2.10.2. Uncertainty Propagation in GIS (098), Gerard Heuvelink 2.10.3. Detecting and Evaluating Errors by Graphical Methods (099), Kate Beard 2.10.4. Data Quality Measurement and Assessment (100), Howard Veregin

o storing uncertainty information

2.11. Visualization and cartography (101)2.11.1. cartographic fundamentals (102) - GC notes

o principles of graphic design; digital output options; scientific visualization; animation and virtual worlds; cognitive basis of visualization

2.12. User interaction (107)

o user interfaces; forms of user interaction with GIS

2.13. Spatial analysis (110)

o combining data; map algebra; terrain modeling; finding and quantifying relationships; generalization; spatial statistics; geostatistics; spatial econometrics; spatial interpolation; spatial search; location/allocation; districting; spatial interaction modeling; cellular automata; distance modeling; neighborhood filtering; pattern recognition; genetic algorithms

2.14. Implementation paradigms (126)2.14.1. Spatial Decision Support Systems (127), Jacek Malczewski - GC notes2.14.2. Exploratory Spatial Data Analysis (128), Robert Haining and Stephen Wise2.14.3. Process Modeling and Simulation (130), Lubos Mitas and Helena Mitsova2.14.4. Multimedia and Virtual Reality (131), George Taylor 2.14.5. WebGIS (133), Kenneth Foote and Anthony Kirvan 2.14.6. Artificial Neural Networks for Spatial Data Analysis (188), Suchi Gopal

o interoperability; object oriented GIS; knowledge based and expert systems; collaborative spatial decision making

3. Geographic Information Technology in Society (135), Robert Maher3.1. Making it work (136), Hugh Calkins and others

o needs assessment; conceptual design of the GIS; survey of available data; evaluating hardware and software; database planning and design; database construction; pilot studies and benchmark tests; acquisition of GIS hardware and software; GIS system integration; GIS application development; GIS use and maintenance

3.2. Supplying the data (143)3.2.1. Public access to geographic information (190), Albert Yeung 3.2.2. WWW Basics (148), Albert Yeung3.2.3. Digital Libraries (191), Albert Yeung 3.2.4. Legal Issues (147) - GC notes and old CC

o transfer standards; national and international data infrastructures; marketing data

3.3. The social context(149)

o digital democracy; geographic information in decision making; human resources and education; ethics of GIS use

3.4. The industry (154)

o history and trends; current products and services; careers in GIS

3.5. Teaching GIS (158), David Unwin3.5.1. Curriculum Design for GIS (159), David Unwin 3.5.2. Teaching and Learning GIS in Laboratories (160), David Unwin

4. Application areas and case studies (161)4.1. Land Information Systems and Cadastral Applications (164), Steve Ventura4.2. Precision Agriculture (194), links to material by PrecisionAg.org

o also: facilities management; network applications; emergency response and E911; recreation, resource management (agriculture, forestry), urban planning and management, environmental health, environmental modeling, emergency management, studying and learning geography, business and marketing (real estate)

If you have comments, please email them to the Karen Doehner.

This page is located at http://www.ncgia.ucsb.edu/giscc/cc_outline.html

NCGIA Core Curriculum in Geographic Information Science

URL: "http://www.ncgia.ucsb.edu/giscc/units/u002/u002.html"

Unit 002 - What is Geographic Information Science?

by Michael F. Goodchild, University of California Santa Barbara

This unit is part of the NCGIA Core Curriculum in Geographic Information Science. These materials may be used for study, research, and education, but please credit the author, Michael F. Goodchild, and the project, NCGIA Core Curriculum in GIScience. All commercial rights reserved. Copyright 1997 by Michael F. Goodchild.

Your comments on these materials are welcome. A link to an evaluation form is provided at the end of this document.

Advanced Organizer

Topics covered in this unit

definitions of geographic information, GI technologies, GI systems and GI science

Learning Outcomes

after learning the material covered in this unit, students should be able to:o define basic terms associated with geographic information including

technologies, systems, science, studieso explain why geographic information systems are importanto explain why a science of geographic information is neededo know where to look for more information on these topics

Full Table of Contents

Instructors' Notes

Metadata and Revision History

What is Geographic Information Science?

1. Opening definitions

1.1. Geographic information

is information about places on the Earth's surface knowledge about where something is knowledge about what is at a given location

can be very detailed, for example:o information about the locations of all buildings in a cityo information about individual trees in a forest

can be very coarse, for example:o climate of a large regiono population density of an entire country

in these examples it's the geographic resolution that varies

other characteristics of geographic information are:o often relatively static

natural features and many features of human origin don't change rapidly

only static information can be portrayed on a static paper mapo can be very voluminous

a terabyte (1012 bytes) of data is sent from a single satellite in one day

gigabytes (gigabyte = 109 bytes) of data are needed to describe the US street network

1.2. Digital geographic information

geographic information expressed in digital formo coded in an alphabet that uses only two characters (0 or 1), called bitso data is represented as sequences of bitso GISCC section "Defining characteristics of computing technology" will

explore this topic once a package of information is in digital form, it looks like any other package

of information - a 'bag of bits'o many kinds of information can be handled by the same technology

a digital disk can store words, numbers, maps, sounds the Internet can transmit any type of information

1.3. Geographic information technologies

are technologies for collecting and dealing with geographic information there are three main types:

1.3.1. Global Positioning System (GPS)

a system of Earth-orbiting satellites transmitting precisely timed signalso a similar system deployed by the Russian Federation is called

GLONASS (global navigation satellite system) signals are received by a special electronic device

o the smallest versions are hand-held and even smaller provides direct measurement of position on the Earth's surface location is expressed in latitude/longitude or other standard system see GISCC section Global Positioning Systems

1.3.2. Remote sensing

use of Earth orbiting satellites to capture information about the surface and atmosphere below

satellites vary depending on how much detail can be seen, what parts of the electromagnetic spectrum are sensed

signals transmitted to Earth receiving stations where they are transformed for dissemination as digital images

see the Remote Sensing Core Curriculum

1.3.3. Geographic information system (GIS)

a system for input, storage, manipulation, and output of geographic information a class of software a practical instance of a GIS combines software with hardware, data, a user,

etc., to solve a problem, support a decision, help to plan the next section is a basic introduction to GIS

2. What is GIS?

GIS stands for "geographic information system"o is a special kind of "information system"

information systems are used to manipulate, summarize, query, edit, visualize - generally, to work with information stored in computer databases

a commonly encountered application are the information systems used by airlines and travel agents to make reservations, check in passengers, etc.

o uses special information about what is where on the Earth's surface there are many kinds of information used in computers

o numbers: computers are used to add, multiply, divide, ...

o text: computers are used as word processors to create, edit, send, and receive text

o pictures: computers are used as image processors

o lists, tables in spreadsheets

o sounds in music synthesizers

o maps and images of the Earth's surface in GIS

why use computers to handle information?o easy to store, retrieve, query, manipulate, send, receive, copy, display...

most of these things can be done by hand, but only slowly paper maps are difficult to handle, store, send, receive, copy...

o GIS makes all of these operations easier today, all kinds of information are being handled in computers

o good to have one place to go for all kinds of informationo one system (the Internet) used to send, receive all kinds

2.1. What does a GIS look like? How would I know one if I saw one?

are two distinct meanings of the question "is this a GIS?"1. GIS is a real application, including the hardware, data, software and

people needed to solve a problem (a GIS application)2. GIS is a type of software sold by a software developer (compare

Microsoft Word) will focus on #1 first

GIS hardware is like any other computer (nothing special about the hardware)o keyboard, display monitor (screen), cables, Internet connection

with some extra components perhapso maps come on big bits of paper

need specially big printers and plotters to make map output from GIS

need specially big devices to scan and input data from maps to GIS

digitizers, scannerso but not all GISs will need these

what is important is the kind of information that's storedo information about what is where

the contents of maps and imageso you would know a computer was being used for GIS because the data

stored in it would include maps and images but in addition, a GIS includes the tools to do things with this information

o special functions that work on geographic informationo functions to:

display on the screen

edit, change, transform measure distances, areas combine maps of the same area together

o those were simple, but functions can be much more sophisticated keep inventories of what is where manage properties, facilities judge the suitability of areas for different purposes help users make decisions about places, to plan make predictions about the future

o these sophisticated functions require human expertise as well

the functions that a GIS can perform are part of its softwareo now we are into the second meaning above - a GIS is a type of softwareo the user combines the software with his or her data and performs various

functionso this software will probably have been supplied by a company that

specializes in GISo the price of the software may be anywhere from $50 to $50,000o there are many different GIS software vendors

some specialize in GIS for others, GIS is one of many markets for their products

there are several other versions of "What is GIS on the net"o see the Web References section below

2.2. What is GIS used for?

why go to all this trouble and expense? who needs to know what is where? here are just a few of the most important uses:

2.2.1. Utility companies

includes gas, phone, electric, water, cable TV companies a single company may have hundreds of thousands of customers

o each with a connection to the networko plus thousands of miles of wires, underground pipeso with transformers, switches, poles...o representing billions of dollars of installed infrastructure

a utility company receives thousands of maintenance calls per day they need to:

o keep track of all this activityo maintain accurate information about what is where

o keep records up to dateo make daily work assignments to crewso provide information to others

e.g. another company wishes to dig up a street, what do they need to avoid?

2.2.2. Transportation

a state department of transportation needs too store information on the state of pavement everywhere on the state

highway networko maintain an inventory of all highway signso analyze data on accidents, look for 'black spots'

a traveling salesperson needso a system in the car for finding locations, routes

a delivery company, e.g. Federal Express, UPS, needs too keep track of shipments, know where they areo plan efficient delivery routes

a school bus operator needs too plan efficient collection routes

a transit authority needs too know where transit vehicles are at all times

studies have shown substantial savings when routes and schedules are managed using GIS

2.2.3. Farmers

increasingly use detailed maps and images to plan cropso analyze yieldso plan efficient application of fertilizers, chemicals

these techniques are known as precision agriculture

2.2.4. Forestry

need to keep track of what timber is growing where need to be able to plan timber harvest

o how to provide for timber needs now, but maintain a healthy forest resource for the future

need to plan locations of roads, methods of cutting and removing logs to comply with environmental regulations

need to manage forests for many purposes, including recreation

3. Systems, science and studies

what does it mean to be "doing GIS"?o for a lengthier discussion see Wright, Goodchild, and Proctor (1997)

it might mean using the tools of Geographic Information Systems to solve a problem

o such as those in the previous exampleso a GIS project might have the following stages:

1. define the problem2. acquire the software (and the hardware?)3. acquire the data4. clean the database5. perform the analysis6. interpret and present the results

or it might mean helping to build the toolso adding to existing geographic information technologieso helping to invent or develop new ones

or it might mean studying the theory and concepts that lie behind GIS and the other geographic information technologies

o thus GIS = Geographic Information Science

a different way of decoding the acronym 'GIS'o more discussion followso Goodchild (1992) discusses what a GIScience might be in detail

Forer and Unwin (1997) add a fourth varianto is a third way of decoding 'GIS' = Geographic Information Studieso are studies of the societal context of geographic information

the legal context issues of privacy, confidentiality economics of geographic information

4. Geographic information science (finally!)

is the science behind the technologyo considers fundamental questions raised by the use of systems and

technologieso is the science needed to keep technology at the cutting edge

is a multidisciplinary fieldo many disciplines contribute to these issues

e.g. cartography, geodesy, photogrammetry, ... today we should extend the list to include areas like cognitive

psychology, spatial statisticso the terms 'geomatics' and 'geoinformatics' have similar meaning

'geomatics' is more popular in Europe and Canada is it 'spatial' or 'geographic'?

o 'geographic' has to do with the Earth its two-dimensional surface its three-dimensional atmosphere, oceans, sub-surface

o 'spatial' has to do with any multi-dimensional frame medical images are referenced to the human body engineering drawings are referenced to a mechanical object architectural drawings are referenced to a building

o 'geographic' is a subset of 'spatial' often the terms are used interchangeably

o 'geospatial' is sometimes used does 'geographic' sound too 'soft'?

4.1. The big questions of GIScience

what questions does GIS raise?o or geographic technologies in general

questions of representationo the Earth's surface is infinitely complex

decisions must be made about how to capture it, represent it in a digital system

about how and where to sample about what data format options to use

o what criteria can be used to select a representation? accuracy of representation accuracy of predictions, decisions based on representation minimizing volume of data maximizing speed of computation compatibility with other projects, users, software compatibility with how people actually think about the world

how to assess a representationo how to measure its accuracyo how to measure what's missing, its uncertaintyo how to express these in ways that are meaningful to the user

how to describe them in documentation how to visualize them how to simulate their impacts

questions about the relationship between the representation and the usero how to people, rather than machines, think about the world?o how can computer representations be made more like the ways people

think?o how do people reason with, learn about, communicate about the

geographical world?o how can output from GIS be made more intelligible

to certain types of users, e.g. children under certain constrained situations, e.g. in a fighter cockpit

questions about data models and structureso how to store a given representation efficientlyo how to retrieve information rapidly through appropriate indexingo how to achieve interoperability between systems

questions about the display of geographic datao how do methods of display affect the interpretation of geographic data?o how can the science of cartography be extended to take advantage of the

power of the digital environment?o what basic properties of display determine its success?

questions about analytical toolso what is the nature of human spatial intuition, and how can it be enhanced

by GIS tools?o what methods of analysis are needed to support specific types of

decisions made using GIS?o how can methods of analysis be presented so that users can choose

effectively between them? there are many other big questions

o a quick look at recent books and papers in the GIS research literature will suggest many more

the University Consortium for Geographic Information Science is a group of over 30 U.S. universities dedicated to promotion of GIScience

o the UCGIS research agenda includes many important and current research areas in GIScience

o see http://www.ucgis.org

4.2. The disciplines of GIScience

disciplines that have traditionally researched geographic information technologies

o cartography, the science (and art) of map-makingo remote sensing, the science of Earth observation from spaceo geodesy, the science of accurate measurement of the Eartho surveying, the science of accurate measurement of natural and human-

made features on the Eartho photogrammetry, the science of measurement from photographs and

imageso image processing, the science of handling and analysis of image data

disciplines that have traditionally researched digital technology and information in general

o computer science, particularly: databases computational geometry image processing, pattern recognition

o information science disciplines that have traditionally studied the Earth, particularly its surface and

near-surface, in either physical or human aspecto geologyo geophysicso oceanographyo agricultureo biology, particularly ecology, biogeographyo environmental scienceo geographyo sociologyo political scienceo anthropologyo and many moreo these sciences are all potential users of GIS

disciplines that have traditionally worked to integrate knowledge from different disciplines, within the context of the Earth's surface

o geographyo environmental scienceo newer fields like global change, integrated assessment

disciplines that have traditionally studied the nature of human understanding, and its interactions with machines

o psychology, particularly cognitive psychology, environmental psychology

o cognitive scienceo artificial intelligence

4.3. How do I find out more about GIS and GIScience?

besides studying further in this curriculumo look up the references given below o surf the Web o settle down with a good book

5. Summary

geographic information is information about places on the earth's surface geographic information technologies include global positioning systems (GPS),

remote sensing and geographic information systems. geographic information systems are both computer systems and software GIS can have many different manifestations GIS is used for a great variety of applications geographic information science is the science behind GIS technology

6. Review and study questions

1. What do 'geographic' and 'spatial' mean, and why is the term 'geospatial' popular?

2. Identify any traditional disciplines missing from the lists given in the unit and explain their relationship to GIScience.

3. Explain why geographic information science should or should not be a distinct discipline:

o with its own journals.o with its own departments.o with its own degrees.

4. Cartography was identified as both a science and an art; why is this, and why were other disciplines not similarly identified?

5. It is tempting to think of a GIS as a computer containing maps but is that not like talking about the automobile as a horseless carriage? Explain why this vision is limiting.

7. References

7.1. Print references

7.1.1. Cited references

Forer, P., and D.J. Unwin (1997) Enabling progress in GIS and education. In P.A. Longley, M.F. Goodchild, D.J. Maguire, and D.W. Rhind (editors) Geographical Information Systems: Principles, Techniques, Management and Applications. Cambridge: GeoInformation International.

Goodchild, M.F. (1992) Geographical information science. International Journal of Geographical Information Systems 6(1): 31-45.

Wright, D.J., M.F. Goodchild, and J.D. Proctor (1997) Demystifying the persistent ambiguity of GIS as "tool" versus "science". Annals of the Association of American Geographers 87(2): 346-362.

7.1.2. Basic and practical introductions to GIS

John C. Antenucci and others (1991) Geographic Information Systems: A Guide to the Technology. New York : Van Nostrand Reinhold.

Tor Bernhardsen (1992) Geographic Information Systems. Arendal, Norway: Viak (but widely available in the US).

Keith C. Clarke (1997) Getting Started with Geographic Information Systems. Upper Saddle River, NJ: Prentice Hall.

Michael N. DeMers (1997) Fundamentals of Geographic Information Systems. New York: J. Wiley & Sons.

references to more advanced books will be found elsewhere in this curriculum

all of these and many others are obtainable through online GIS 'bookstores':o http://www.esri.com o http://www.geoplace.com

7.1.3. GIS magazines

o GIS World - http://www.geoplace.como Geo Info Systems - http://www.geoinfosystems.com

7.2. Web references

some cool sites that do GIS over the Webo http://www.mapquest.com o http://www.esri.com and try the live demos

sites of some major GIS software vendorso http://www.esri.com o http://www.intergraph.com o http://www.autodesk.com

some other introductions to GISo USGS GIS Tutorial - http://www.usgs.gov/research/gis/title.htmlo The Geographer's Craft

-http://www.utexas.edu/depts/grg/gcraft/notes/intro/intro.htmlo Nick Chrisman's "What is GIS?"

-http://faculty.washington.edu/chrisman/G460/Lec02.htmlo ESRI's About GIS

- http://www.esri.com/library/gis/abtgis/what_gis.html o The Essential Guide to GIS

- http://giswww.kingston.ac.uk/ESGUIDE/start.htmlo "What is GIS?" from Australia - http://www.dlsr.com.au/whatgis.htm

check the GIS magazine websites listed above

Evaluation

We are very interested in your comments and suggestions for improving this material. Please follow the link above to the evaluation form if you would like to contribute in this manner to this evolving project..

Citation

To reference this material use the appropriate variation of the following format:Michael F. Goodchild. (1997) What is Geographic Information Science?, NCGIA Core Curriculum in GIScience, http://www.ncgia.ucsb.edu/giscc/units/u002/u002.html, posted October 7, 1997.

The correct URL for this page is: http://www.ncgia.ucsb.edu/giscc/units/u002/u002.html. Created: July 24, 1997. Last revised: October 7, 1997.

Gateway to the Core Curriculum

NCGIA Core Curriculum in Geographic Information Science

URL: "http://www.ncgia.ucsb.edu/giscc/units/u002/u002.html"

Unit 002 - What is Geographic Information Science?

by Michael F. Goodchild, University of California Santa Barbara

This unit is part of the NCGIA Core Curriculum in Geographic Information Science. These materials may be used for study, research, and education, but please credit the author, Michael F. Goodchild, and the project, NCGIA Core Curriculum in GIScience. All commercial rights reserved. Copyright 1997 by Michael F. Goodchild.


Advanced Organizer


definitions of geographic information, GI technologies, GI systems and GI science

Learning Outcomes

after learning the material covered in this unit, students should be able to:o define basic terms associated with geographic information including

technologies, systems, science, studieso explain why geographic information systems are importanto explain why a science of geographic information is neededo know where to look for more information on these topics


Instructors' Notes


What is Geographic Information Science?

1. Opening definitions

1.1. Geographic information

is information about places on the Earth's surface knowledge about where something is knowledge about what is at a given location

can be very detailed, for example:o information about the locations of all buildings in a cityo information about individual trees in a forest

can be very coarse, for example:o climate of a large regiono population density of an entire country

in these examples it's the geographic resolution that varies

other characteristics of geographic information are:o often relatively static

natural features and many features of human origin don't change rapidly

only static information can be portrayed on a static paper mapo can be very voluminous

a terabyte (1012 bytes) of data is sent from a single satellite in one day

gigabytes (gigabyte = 109 bytes) of data are needed to describe the US street network

1.2. Digital geographic information

geographic information expressed in digital formo coded in an alphabet that uses only two characters (0 or 1), called bitso data is represented as sequences of bitso GISCC section "Defining characteristics of computing technology" will

explore this topic once a package of information is in digital form, it looks like any other package

of information - a 'bag of bits'o many kinds of information can be handled by the same technology

a digital disk can store words, numbers, maps, sounds the Internet can transmit any type of information

1.3. Geographic information technologies

are technologies for collecting and dealing with geographic information there are three main types:

1.3.1. Global Positioning System (GPS)

a system of Earth-orbiting satellites transmitting precisely timed signalso a similar system deployed by the Russian Federation is called

GLONASS (global navigation satellite system) signals are received by a special electronic device

o the smallest versions are hand-held and even smaller provides direct measurement of position on the Earth's surface location is expressed in latitude/longitude or other standard system see GISCC section Global Positioning Systems

1.3.2. Remote sensing

use of Earth orbiting satellites to capture information about the surface and atmosphere below

satellites vary depending on how much detail can be seen, what parts of the electromagnetic spectrum are sensed

signals transmitted to Earth receiving stations where they are transformed for dissemination as digital images

see the Remote Sensing Core Curriculum

1.3.3. Geographic information system (GIS)

a system for input, storage, manipulation, and output of geographic information a class of software a practical instance of a GIS combines software with hardware, data, a user,

etc., to solve a problem, support a decision, help to plan the next section is a basic introduction to GIS

2. What is GIS?

GIS stands for "geographic information system"o is a special kind of "information system"

information systems are used to manipulate, summarize, query, edit, visualize - generally, to work with information stored in computer databases

a commonly encountered application are the information systems used by airlines and travel agents to make reservations, check in passengers, etc.

o uses special information about what is where on the Earth's surface there are many kinds of information used in computers

o numbers: computers are used to add, multiply, divide, ...

o text: computers are used as word processors to create, edit, send, and receive text

o pictures: computers are used as image processors

o lists, tables in spreadsheets

o sounds in music synthesizers

o maps and images of the Earth's surface in GIS

why use computers to handle information?o easy to store, retrieve, query, manipulate, send, receive, copy, display...

most of these things can be done by hand, but only slowly paper maps are difficult to handle, store, send, receive, copy...

o GIS makes all of these operations easier today, all kinds of information are being handled in computers

o good to have one place to go for all kinds of informationo one system (the Internet) used to send, receive all kinds

2.1. What does a GIS look like? How would I know one if I saw one?

are two distinct meanings of the question "is this a GIS?"1. GIS is a real application, including the hardware, data, software and

people needed to solve a problem (a GIS application)2. GIS is a type of software sold by a software developer (compare

Microsoft Word) will focus on #1 first

GIS hardware is like any other computer (nothing special about the hardware)o keyboard, display monitor (screen), cables, Internet connection

with some extra components perhapso maps come on big bits of paper

need specially big printers and plotters to make map output from GIS

need specially big devices to scan and input data from maps to GIS

digitizers, scannerso but not all GISs will need these

what is important is the kind of information that's storedo information about what is where

the contents of maps and imageso you would know a computer was being used for GIS because the data

stored in it would include maps and images but in addition, a GIS includes the tools to do things with this information

o special functions that work on geographic informationo functions to:

display on the screen edit, change, transform measure distances, areas

combine maps of the same area togethero those were simple, but functions can be much more sophisticated

keep inventories of what is where manage properties, facilities judge the suitability of areas for different purposes help users make decisions about places, to plan make predictions about the future

o these sophisticated functions require human expertise as well

the functions that a GIS can perform are part of its softwareo now we are into the second meaning above - a GIS is a type of softwareo the user combines the software with his or her data and performs various

functionso this software will probably have been supplied by a company that

specializes in GISo the price of the software may be anywhere from $50 to $50,000o there are many different GIS software vendors

some specialize in GIS for others, GIS is one of many markets for their products

there are several other versions of "What is GIS on the net"o see the Web References section below

2.2. What is GIS used for?

why go to all this trouble and expense? who needs to know what is where? here are just a few of the most important uses:

2.2.1. Utility companies

includes gas, phone, electric, water, cable TV companies a single company may have hundreds of thousands of customers

o each with a connection to the networko plus thousands of miles of wires, underground pipeso with transformers, switches, poles...o representing billions of dollars of installed infrastructure

a utility company receives thousands of maintenance calls per day they need to:

o keep track of all this activityo maintain accurate information about what is whereo keep records up to dateo make daily work assignments to crews

o provide information to others e.g. another company wishes to dig up a street, what do they need

to avoid?

2.2.2. Transportation

a state department of transportation needs too store information on the state of pavement everywhere on the state

highway networko maintain an inventory of all highway signso analyze data on accidents, look for 'black spots'

a traveling salesperson needso a system in the car for finding locations, routes

a delivery company, e.g. Federal Express, UPS, needs too keep track of shipments, know where they areo plan efficient delivery routes

a school bus operator needs too plan efficient collection routes

a transit authority needs too know where transit vehicles are at all times

studies have shown substantial savings when routes and schedules are managed using GIS

2.2.3. Farmers

increasingly use detailed maps and images to plan cropso analyze yieldso plan efficient application of fertilizers, chemicals

these techniques are known as precision agriculture

2.2.4. Forestry

need to keep track of what timber is growing where need to be able to plan timber harvest

o how to provide for timber needs now, but maintain a healthy forest resource for the future

need to plan locations of roads, methods of cutting and removing logs to comply with environmental regulations

need to manage forests for many purposes, including recreation

3. Systems, science and studies

what does it mean to be "doing GIS"?o for a lengthier discussion see Wright, Goodchild, and Proctor (1997)

it might mean using the tools of Geographic Information Systems to solve a problem

o such as those in the previous exampleso a GIS project might have the following stages:

1. define the problem2. acquire the software (and the hardware?)3. acquire the data4. clean the database5. perform the analysis6. interpret and present the results

or it might mean helping to build the toolso adding to existing geographic information technologieso helping to invent or develop new ones

or it might mean studying the theory and concepts that lie behind GIS and the other geographic information technologies

o thus GIS = Geographic Information Science

a different way of decoding the acronym 'GIS'o more discussion followso Goodchild (1992) discusses what a GIScience might be in detail

Forer and Unwin (1997) add a fourth varianto is a third way of decoding 'GIS' = Geographic Information Studieso are studies of the societal context of geographic information

the legal context issues of privacy, confidentiality economics of geographic information

4. Geographic information science (finally!)

is the science behind the technologyo considers fundamental questions raised by the use of systems and

technologieso is the science needed to keep technology at the cutting edge

is a multidisciplinary fieldo many disciplines contribute to these issues

e.g. cartography, geodesy, photogrammetry, ... today we should extend the list to include areas like cognitive

psychology, spatial statisticso the terms 'geomatics' and 'geoinformatics' have similar meaning

'geomatics' is more popular in Europe and Canada is it 'spatial' or 'geographic'?

o 'geographic' has to do with the Earth its two-dimensional surface its three-dimensional atmosphere, oceans, sub-surface

o 'spatial' has to do with any multi-dimensional frame medical images are referenced to the human body engineering drawings are referenced to a mechanical object architectural drawings are referenced to a building

o 'geographic' is a subset of 'spatial' often the terms are used interchangeably

o 'geospatial' is sometimes used does 'geographic' sound too 'soft'?

4.1. The big questions of GIScience

what questions does GIS raise?o or geographic technologies in general

questions of representationo the Earth's surface is infinitely complex

decisions must be made about how to capture it, represent it in a digital system

about how and where to sample about what data format options to use

o what criteria can be used to select a representation? accuracy of representation accuracy of predictions, decisions based on representation minimizing volume of data maximizing speed of computation compatibility with other projects, users, software compatibility with how people actually think about the world

how to assess a representationo how to measure its accuracyo how to measure what's missing, its uncertaintyo how to express these in ways that are meaningful to the user

how to describe them in documentation how to visualize them

how to simulate their impacts questions about the relationship between the representation and the user

o how to people, rather than machines, think about the world?o how can computer representations be made more like the ways people

think?o how do people reason with, learn about, communicate about the

geographical world?o how can output from GIS be made more intelligible

to certain types of users, e.g. children under certain constrained situations, e.g. in a fighter cockpit

questions about data models and structureso how to store a given representation efficientlyo how to retrieve information rapidly through appropriate indexingo how to achieve interoperability between systems

questions about the display of geographic datao how do methods of display affect the interpretation of geographic data?o how can the science of cartography be extended to take advantage of the

power of the digital environment?o what basic properties of display determine its success?

questions about analytical toolso what is the nature of human spatial intuition, and how can it be enhanced

by GIS tools?o what methods of analysis are needed to support specific types of

decisions made using GIS?o how can methods of analysis be presented so that users can choose

effectively between them? there are many other big questions

o a quick look at recent books and papers in the GIS research literature will suggest many more

the University Consortium for Geographic Information Science is a group of over 30 U.S. universities dedicated to promotion of GIScience

o the UCGIS research agenda includes many important and current research areas in GIScience

o see http://www.ucgis.org

4.2. The disciplines of GIScience

disciplines that have traditionally researched geographic information technologies

o cartography, the science (and art) of map-makingo remote sensing, the science of Earth observation from space

o geodesy, the science of accurate measurement of the Eartho surveying, the science of accurate measurement of natural and human-

made features on the Eartho photogrammetry, the science of measurement from photographs and

imageso image processing, the science of handling and analysis of image data

disciplines that have traditionally researched digital technology and information in general

o computer science, particularly: databases computational geometry image processing, pattern recognition

o information science disciplines that have traditionally studied the Earth, particularly its surface and

near-surface, in either physical or human aspecto geologyo geophysicso oceanographyo agricultureo biology, particularly ecology, biogeographyo environmental scienceo geographyo sociologyo political scienceo anthropologyo and many moreo these sciences are all potential users of GIS

disciplines that have traditionally worked to integrate knowledge from different disciplines, within the context of the Earth's surface

o geographyo environmental scienceo newer fields like global change, integrated assessment

disciplines that have traditionally studied the nature of human understanding, and its interactions with machines

o psychology, particularly cognitive psychology, environmental psychology

o cognitive scienceo artificial intelligence

4.3. How do I find out more about GIS and GIScience?

besides studying further in this curriculumo look up the references given below o surf the Web o settle down with a good book

5. Summary

geographic information is information about places on the earth's surface geographic information technologies include global positioning systems (GPS),

remote sensing and geographic information systems. geographic information systems are both computer systems and software GIS can have many different manifestations GIS is used for a great variety of applications geographic information science is the science behind GIS technology

6. Review and study questions

1. What do 'geographic' and 'spatial' mean, and why is the term 'geospatial' popular?

2. Identify any traditional disciplines missing from the lists given in the unit and explain their relationship to GIScience.

3. Explain why geographic information science should or should not be a distinct discipline:

o with its own journals.o with its own departments.o with its own degrees.

4. Cartography was identified as both a science and an art; why is this, and why were other disciplines not similarly identified?

5. It is tempting to think of a GIS as a computer containing maps but is that not like talking about the automobile as a horseless carriage? Explain why this vision is limiting.

7. References

7.1. Print references

7.1.1. Cited references

Forer, P., and D.J. Unwin (1997) Enabling progress in GIS and education. In P.A. Longley, M.F. Goodchild, D.J. Maguire, and D.W. Rhind (editors) Geographical Information Systems: Principles, Techniques, Management and Applications. Cambridge: GeoInformation International.

Goodchild, M.F. (1992) Geographical information science. International Journal of Geographical Information Systems 6(1): 31-45.

Wright, D.J., M.F. Goodchild, and J.D. Proctor (1997) Demystifying the persistent ambiguity of GIS as "tool" versus "science". Annals of the Association of American Geographers 87(2): 346-362.

7.1.2. Basic and practical introductions to GIS

John C. Antenucci and others (1991) Geographic Information Systems: A Guide to the Technology. New York : Van Nostrand Reinhold.

Tor Bernhardsen (1992) Geographic Information Systems. Arendal, Norway: Viak (but widely available in the US).

Keith C. Clarke (1997) Getting Started with Geographic Information Systems. Upper Saddle River, NJ: Prentice Hall.

Michael N. DeMers (1997) Fundamentals of Geographic Information Systems. New York: J. Wiley & Sons.

references to more advanced books will be found elsewhere in this curriculum

all of these and many others are obtainable through online GIS 'bookstores':o http://www.esri.com o http://www.geoplace.com

7.1.3. GIS magazines

o GIS World - http://www.geoplace.como Geo Info Systems - http://www.geoinfosystems.com

7.2. Web references

some cool sites that do GIS over the Webo http://www.mapquest.com o http://www.esri.com and try the live demos

sites of some major GIS software vendorso http://www.esri.com o http://www.intergraph.com o http://www.autodesk.com

some other introductions to GISo USGS GIS Tutorial - http://www.usgs.gov/research/gis/title.htmlo The Geographer's Craft

-http://www.utexas.edu/depts/grg/gcraft/notes/intro/intro.htmlo Nick Chrisman's "What is GIS?"

-http://faculty.washington.edu/chrisman/G460/Lec02.htmlo ESRI's About GIS

- http://www.esri.com/library/gis/abtgis/what_gis.html o The Essential Guide to GIS

- http://giswww.kingston.ac.uk/ESGUIDE/start.htmlo "What is GIS?" from Australia - http://www.dlsr.com.au/whatgis.htm

check the GIS magazine websites listed above

Evaluation


Citation

To reference this material use the appropriate variation of the following format:Michael F. Goodchild. (1997) What is Geographic Information Science?, NCGIA Core Curriculum in GIScience, http://www.ncgia.ucsb.edu/giscc/units/u002/u002.html, posted October 7, 1997.

The correct URL for this page is: http://www.ncgia.ucsb.edu/giscc/units/u002/u002.html. Created: July 24, 1997. Last revised: October 7, 1997.


Unit 005 - The World in Spatial Termsby Reginald G. Golledge1, Daniel Montello1,

and Timothy L. Nyerges2

This unit is part of the NCGIA Core Curriculum in Geographic Information Science. These materials may be used for study, research, and education, but please credit the authors Golledge, Montello, and Nyerges, and the project, NCGIA Core Curriculum in GIScience. All commercial rights reserved. Copyright 1997


Unit Topics

This unit has two primary segments:

Unit 006 - Human Cognition of the Spatial World, by Dan Montello and

Unit 007 - Asking Geographic Questions, by Timothy Nyerges and Reginald G. Golledge

Intended Learning Outcomes

The first section sets the scene by differentiationg between objects and processes and by using fundamental understanding of the spatial world to provide a necessary knowledge base for GIS.

The second section builds on the knowledge base to demonstrate how specific knowledge about objects and spatial relations among them can be unpacked by the mechanism of asking geographic questions.

Author Affiliations

Reg Golledge, Department of Geography, University of California Santa Barbara. E-mail: [email protected]

Dan Montello, Department of Geography, University of California Santa Barbara. E-mail: [email protected]

Timothy Nyerges, Department of Geography, University of Washington. E-mail:[email protected]

The correct URL for this page is: http://www.ncgia.ucsb.edu/giscc/units/u005/u005.html. Last revised: November 3 , 1997.


NCGIA Core Curriculum in Geographic Information ScienceURL: "http://www.ncgia.ucsb.edu/giscc/units/u006/u006.html"

Unit 006 - Human Cognition of the Spatial World

by Daniel R. Montello, Department of GeographyUniversity of California Santa Barbara, [email protected]

This section was edited by Reginald Golledge, Department of Geography, University of California Santa Barbara.

This unit is part of the NCGIA Core Curriculum in Geographic Information Science. These materials may be used for study, research, and education, but please credit the author, Daniel R. Montello and the project,NCGIA Core

Curriculum in GIScience. All commercial rights reserved. Copyright 1997 by Daniel R. Montello.


Advanced Organizer

Unit Topics and learning outcomes

This section sets the scene by differentiating between objects and processes and by using fundamental understanding of the spatial world to provide a necessary knowledge base for GIS.

Instructor's Notes

Table of Contents


Unit 006 - Human Cognition of the Spatial World

1. Introduction

at human scales, the world consists of objects, events, processes, and a background environment

the study of cognition is about knowledge: its acquisition, storage and retrieval, manipulation, and use by humans and other intelligent creatures

o cognition includes sensation and perception, thinking, imagery, reasoning and problem-solving, memory, learning, and language

o cognitive structures and process are part of the mind, which emerges from a brain and nervous system inside of a body that exists in a social and physical world

spatial cognition deals with the cognition of spatial properties of the world, including location, size, distance, direction, shape, pattern, movement, and inter-object relations.

this unit is about spatial cognition and its relevance for Geographic Information Systems

2. Sensing and Perceiving the World

sensation is the first response of the nervous system to stimulation from patterned energy in the world

o sensory systems are organized into modalities, including vision, hearing, smelling, tasting, pressure and texture, temperature, kinesthesis (limb position and movement), and vestibular senses (gravity and body acceleration)

perception is the active acquisition of knowledge about the self and the world through the senses

characteristics of the perceived world:o locational perspective -- world perceived from a point-of-view,

incomplete access to worldo redundancy of information (e.g., depth cues of interposition and linear

perspective)o constancy (color, size, position, shape) -- objects, events, and

background maintain many characteristics even as viewing conditions change

o meaningfulness -- tendency to perceive meaningful, familiar objects and events

3. Cognitive Maps

are internal representations of the world and its spatial properties stored in memory (also called "mental maps")

o what's out there, what are its attributes, where it is, how to get thereo are both idiosyncratic to individuals, and shared among groups

not like a cartographic map in the heado not a unitary representation with a constant scale, not completely

integratedo consists of discrete pieces (more vector than raster)

landmarks, routes and regions pieces determined by physical, perceptual, or conceptual

boundarieso hierarchically organized pieces

multiple levels of pieces differing in status (e.g., size) relation of containment between levels pieces within a level not completely connected hierarchies revealed by patterns of errors or times to respond to

questions about the relative locations of places within and between pieces

o spatial information not well modeled by metric geometries (such as high school Euclidean geometry)

o emotional associations too (connotative meaning)

distortions in cognitive mapso distortions tell us about properties of cognitive mapso how is accuracy of knowledge defined?

correspondence to physical measurement group consensus behavioral adaptiveness (does it work?)

o examples continents are aligned, e.g., South America is thought to be due

south of North America when it is actually southeast road intersections and barriers increase apparent distances

between places turns are remembered more like right angles and curved lines are

often straightened

4. Spatial Learning and Development

learning is a relatively permanent change in cognition or behavior that results from practice or experience

spatial knowledge is learned via one or more media of acquisitiono direct sensorimotor experience, maps, models, photos and drawings,

movies and videos, verbal and written language, virtual spaceso media has consequences for nature of acquired knowledge

cognitive development is systematic change in the content and process of cognition over time, including learning, maturation, and growth (child or adult)

o child psychologist Piaget known for a qualitative "stage theory" of cognitive development of children

change from concrete sensorimotor space in infancy to abstract spatial reasoning in adolescence

"frame of reference" used to define locations changes from egocentric (self-centered) to allocentric (externally referenced)

geometry of spatial knowledge changes from topological to projective and metric

o information-processing approach provides an alternative theory of continuous and quantitative development

traditional theory of developmental sequence in spatial knowledge of the world inspired by Piagetian theory; consists of 3 stages or elements, acquired over time

o first is "landmark knowledge": unique patterns of perceptual events that identify a place

o second is "route knowledge": sensorimotor routines that connect ordered sequences of landmarks; little or no metric spatial knowledge

o third is "survey knowledge": two-dimensional layout knowledge of simultaneous interrelations of locations; allows detouring, shortcutting, and creative navigation

information-processing approach inspires an alternative sequence of continuous and quantitative increase in extent, accuracy, and completeness of sometimes crude metric spatial knowledge

5. Navigation

navigation is coordinated and goal-directed route following through space

"metaphorical navigation" through a math problem, text, computer menu system, computer network

consists of 2 components: locomotion and wayfinding locomotion is guidance through space in response to local sensorimotor information in immediate surrounds

find support surfaces, avoid obstacles and barriers, follow beacons, move through openings modes: crawling, walking, bikes, cars, planes, etc.

wayfinding is planning and decision-making in response to nonlocal information, undertaken to reach goal

route-choice, destination scheduling, orientation to nonperceptible features, giving directions

two fundamental processes of orientation during navigationo landmark-based or pilotage ("taking-a-fix") is orientation by recognition

of external featureso dead reckoning is orientation relative to a start location by integrating

information about velocity or acceleration during movement, without reference to recognized features

navigation is carried out via skills that vary in their demands on attentional capacity

o relatively automatic skills do not demand much attention, such as locomotion in "normal" environments, following familiar routes to work, etc.

o controlled or effortful skills demand focussed attention, such as wayfinding in unfamiliar environments, giving directions, etc.

6. Using and Learning Maps

major purpose of cartographic maps is to communicate geographical information and support geographical problem-solving

o how do maps effectively communicate? humans fantastic at quickly extracting great amounts of

information from spatial depictions (images) like pictures or graphs

even nonspatial or nonperceivable information can be displayed this way (visualization or spatialization)

maps use convenient scales and viewing perspectives (you can perceive all from a single viewpoint)

maps highlight and clarify relevant properties; omit or downplay irrelevant properties

o how can maps confuse or distort communication? projections, generalizations, exaggerations, omissions may

mislead or distort knowledge scale translations between maps or between map and world are

difficult perspective translation from overhead to terrain-level view may be

confusing interpretation of symbols (colors, point symbols, contour lines)

may be difficult or misleading

training and experience with maps changes the way they are perceived and interpreted

maps show robust "alignment effects", especially when used for navigationo confusing if not oriented with the top of map as the direction you are

facing when viewing it (such as "you-are-here" maps)o such misalignment causes errors and delays

7. Spatial Language

spatial information often expressed verbally

giving verbal directions, spatial descriptions in stories, road signs, computer queries

producing spatial language often requires translation of nonverbal spatial knowledge, which can alter the knowledge some properties of spatial language

nearly all grammatical classes can express spatial information, but especially prepositions

prepositions often ambiguous, difficult to translate into other languages "the house on the lake" vs. "the boat on the lake"; "water in a cup" vs. "crack in a cup"

language expresses mostly nonquantitative or imprecise quantitative ("fuzzy") information about space; connections and general location more important

for example, we say "turn left at the gas station", not "turn 80° after you go .6 miles"

quantitative precision usually unnecessary or even confusing for verbal communication (not always)

context is critical in interpreting spatial language context provided by who is speaking, situation, preceding events, etc. spatial quantity terms: near, far, small, large spatial location terms: here, there, left, right

language often uses spatial metaphors for nonspatial concepts examples: "roundabout argument", "lost in life", "success is dead ahead", "encroach on my space"

verbal directionso person giving directions makes assumptions about questioner's ability to

understand the directionso what makes the best directions?

landmarks and actions only, or an overall description of the space?

how do gestures and maps help? how are they combined with words?

how much quantitative precision is best? should corrective or overshoot statements be given?

o many ambiguities in verbal directions what's a block? what's an intersection? what's a right turn when 5

streets come together? "you can't miss it": what does that mean, why do we say it, how

do we decide when to say it?

8. Relevance to GIS

GISs are frequently difficult to use effectively and efficiently and have not nearly reached their potential

o costs more time and money than it needs to, is more difficult and unpleasant to use than it has to be, and does not perform all of the tasks that it might

limitations and problems could be improved with greater attention to cognitive issues in GIS

o how do humans acquire, reason about, and communicate knowledge with GIS

o cognitive issues touch on all three major functions of GIS: the storage, representation, and analysis of earth-referenced data

some examples of cognitive issues in GISo how experts and laypeople conceptualize and reason about geographical

space, and how GIS can be designed and taught to support both classes of users

o how people express spatial information in natural language (such as English), and how this can be used to understand communication with a GIS in natural language (such as a navigation computer inside a car)

o how interfaces should be designed to promote accurate and efficient communication of spatial and geographic information, such as scale, uncertainty, and network structure

9. Exam and Discussion Questions

1. Discuss ways that the cognitive map is like and unlike a cartographic map. Give some examples of phenomena that support your position.

2. The traditional theory of how spatial knowledge develops over time in a new environment is inspired by the child psychology of Piaget. Describe this traditional theory. What sorts of evidence would support various parts of the traditional theory? What sorts of evidence would argue against parts of the traditional theory?

3. There is a great deal of interest in creating GISs that can directly communicate with users in their own language. Discuss at least two applications where this goal makes sense. Considering the properties of language, especially spatial language, what are some of the problems that must be solved to make language-competent GISs a reality?

4. An argument has been made above that GIS can be improved by understanding human perception and cognition. Review and discuss this argument. In what ways do you agree or disagree with the argument?

10. ReferencesReviews of perception and cognition may be found in any psychology textbook in those areas.

Golledge, R.G., 1987. "Environmental cognition", in D. Stokols and I. Altman, editors, Handbook of environmental psychology. Wiley, New York, 131-174. Reviews 25 years of research in geography, psychology, and related disciplines.

Mark, D.M., and A.U. Frank, editors, 1991. Cognitive and linguistic aspects of geographic space. Kluwer Academic Publishers, Dordrecht, The Netherlands.

Contains many chapters examining cognitive and linguistic issues in GIS from a variety of disciplines.

Montello, D.R., and S.M. Freundschuh, 1995. "Sources of spatial knowledge and their implications for GIS: An introduction", Geographical Systems 2:169-176. Concise overview of several perceptual and cognitive issues relevant to GIS.

Tversky, B., 1992. "Distortions in cognitive maps", Geoforum 23:131-138. Readable and concise review of research on the structure of cognitive maps, patterns of distortions, etc.

Evaluation

We are very interested in your comments and suggestions for improving this material. Please follow the link above to the evaluation form if you would like to contribute in this manner to this evolving project.

Citation

To reference this material use the appropriate variation of the following information:

by Dan Montello, NCGIA Core Curriculum in GIS, National Center for Geographic Information and Analysis, University of California, Santa Barbara, Unit 006,http://www.ncgia.ucsb.edu/giscc/units/u006/u006.html, posted November 5, 1997.

The correct URL for this page is: http://www.ncgia.ucsb.edu/giscc/units/u006/u006.html. Last revised: November 5, 1997.


Unit 007 - Asking Geographic Questionsby: Timothy L. Nyerges, Department of Geography,

University of Washington, e-mail: [email protected] Reginald G. Golledge, Department of Geography,

Univ. of Calif. Santa Barbara, e-mail: [email protected]

This section was edited by Reginald Golledge, Department of Geography, University of California Santa Barbara.

This unit is part of the NCGIA Core Curriculum in Geographic Information Science. These materials may be used for study, research, and education, but please credit the authors, Timothy Nyerges and Teg Golledge, and the project, NCGIA Core Curriculum in GIScience. All commercial rights reserved. Copyright 1997 by Timothy Nyerges.


Advanced Organizer

Unit Topics

Learning Outcomes

Instructor's Notes

Table of Contents


Unit 007 - Asking Geographic Questions

1. Introduction

Questions are designed to encourage thinking and learning.o They do this by posing a problem which requires an answer.

Answers sometimes involve creatively integrating, rearranging, or manipulating bits of information stored in long-term memory or currently being perceived.

o Often hitherto unnoticed connections between facts or constructs may be made when answering a question.

Deriving inspiration from Slater�s monograph Learning Through Geography(1982), Nyerges has developed a set of critical thinking questions to stimulate students� curiosity about geography and GIS (Nyerges, 1991).

Nyerges (1991) suggests that geographic questions can be categorized into those dealing with:

1. location and extent;2. distribution and pattern or shape;3. spatial association;4. spatial interaction; and5. spatial change.

In documenting some of the essential steps and stages one goes through when asking and solving geographic questions, the following material draws extensively on the works of Piper (1976), Slater (1982) Nyerges (1991), and Golledge (1996).

2. The process of enquiry

To begin, consider the following summary of the process of enquiryo Table 1 - The process of enquiry - the skills dimension

To elaborate on the above table, Slater (1982) and later Nyerges (1991) have discussed each of the tabular components in the following ways.

2.1. Research the Questions and Gather Data

Step 1: Identify and clarify questions, issues and problems.

1. Identify central questions and issues.2. Identify value questions.3. Detect ambiguity and vagueness of statement.4. Restate questions, problems, issues in clear, precise, unambiguous terms.5. Identify elements of a question, problem, issue in need of further

clarification.6. Identify the "valuing" elements in a question, issue, problem.7. Identify areas of conflict (especially conflicting values) in a question,

issue, problem.8. Identify areas in need of investigation.9. Distinguish between direct questions and hypothetical questions.10.Formulate hypotheses.11.Identify appropriate procedures for testing hypotheses.

Step 2: Gather and organize data.

1. Locate data.2. Locate sources of data.3. Use of data gathering techniques (e.g. sampling, surveys, questionnaires,

interviews, content analysis, focus group, case studies and so on).4. Select appropriate data.5. Record data.6. Classify data.7. Summarize data.8. Present data.9. Select appropriate techniques for treatment of data.

2.2. Process the Data

Step 1: Interpret the data.

1. Understand form in which data is presented.2. Retrieve basic information from single data source.3. Retrieve detailed/less obvious information from single data source.4. Retrieve complex information from single data source.5. Retrieve information requiring use of more than one data source.6. Compare data from different sources.7. Distinguish between fact and opinion/speculation.8. Distinguish between specific facts and general facts (empirical

generalizations)

9. Distinguish between factual statements and conditional or hypothetical statements.

10.Distinguish between factual statements and value judgements.11.Distinguish between factual statements and normative statements.

Step 2: Analyze the data.

1. Recognize underlying assumptions.2. Following a line of argument (especially where this from an

unfamiliar/unconventional point of view)3. Determine the point of view of author.4. Detect logical flaws in an argument.5. Detect unwarranted assertions, inferences, conclusions, etc.6. Detect relationships, e.g., causal, chronological, concurrent, etc.7. Make warranted inferences/extrapolations from the data.8. Make warranted interpolations where there are gaps in the data.9. Draw warranted conclusions from the data.10.Make warranted predictions of trends, consequences, etc. from the data.11.Discern factors which may affect the accuracy of predictions.12.Formulate hypotheses to account for effects observed in the data.

Step 3: Evaluate evidence.

1. Recognize stereotypes and cliches.2. Detect emotive elements in the presentation.3. Detect bias and prejudice in the presentation.4. Detect motive/purpose in the presentation.5. Detect persuasive techniques used in propaganda, advertising, etc.6. Distinguish between verifiable and unverifiable data.7. Distinguish between relevant and irrelevant information.8. Distinguish between essential and incidental information.9. Assess the adequacy/ inadequacy of data.10.Assess the appropriateness or inappropriateness of the data.11.Determine the consistency/inconsistency of the data.12.Determine whether facts support a generalization, conclusion or

inference.13.Assess the reliability of data sources.14.Recognize limitations/qualifications in the data.15.Distinguish between anecdotal evidence and objective data.

2.3. Reach and Apply Generalizations

Step 1: Generalize.

1. Detect common elements in data.2. Detect relationships in data which could lead to valid generalizations.3. Detect limitations/deficiencies/gaps in data which could render

generalizations valid.4. Modify or reject hypotheses on the basis of evidence.5. Formulate valid generalizations.6. Recognize limitations/ probability factors in generalizations involving

appropriate phenomena in a geographic context.7. Recognize the tentative nature of generalizations involving phenomenon

in a geographical context.8. Discern factors (e.g., change) which may affect the validity of

generalizations.

Step 2: Draw conclusions.

1. Suggest tentative solutions to making tentative decisions in relation to questions/issues/problems.

2. Posing alternative solutions of decisions to problems.3. Examine relative merits of alternative solutions or decisions to problems.4. Propose suitable courses of action in relation to problems in a

geographical context.5. Propose appropriate techniques for reaching generalizations and finding

solutions to questions/issues/problems of a geographical nature.6. Predict probable consequences of a course of action/inaction.7. Identify areas in need of further evidence or investigation.

Step 3: Make value judgments.

1. Formulating reasoned value judgments.2. Defend a value position.3. Examine the implications of alternative value positions.4. Suggest resolution of value conflicts.

2.4. Re-Evaluate

Step 1: Re-evaluate the decision.

3. Examples of geographic questions

While Piper, Slater and Nyerges provide a very detailed framework that a researcher should go through when posing and elaborating geographic questions, we return now to Slater (1982) for specific examples of the types of questions that geographers should be prepared to ask.

The set of questions that Slater suggests should be in every geography inventory include the following:

o Where is it?o Where does it occur?o What is there?o Why is it there?o Why is it not elsewhere?o What could be there?o Could it be elsewhere?o How much is there at that location?o Why is it there rather than anywhere else?o How far does it extend already?o Why does it take a particular form or structure that it has?o Is there regularity in its distribution?o What is the nature of that regularity?o Why should the spatial distributional pattern exhibit regularity?o Where is it in relation to others of the same kind?o What kind of distribution does it make?o Is it found throughout the world?o Is it universal?o Where are its limits?o What are the nature of those limits?o Why do those limits constrain its distribution?o What else is there spatially associated with that phenomenon?o Do these things usually occur together in the same places?o Why should they be spatially associated?o Is it linked to other things?o Has it always been there?o When did it first emerge or become obvious?o How has it changed spatially (through time)?o What factors have influenced its spread?o Why has it spread or diffused in this particular way?

o What geographic factors have constrained its spread?

4. Conclusion

Slater (1982) argues thato in order to answer some of these questions, geographical investigation

requires that individuals practice their skills of observing, defining, classifying, analyzing, inferring, reasoning, integrating, and associating phenomena, and

o doing so will train both the teacher and the students in the use of geographic thinking and transfer their ability to handle the processes which, if followed, can help solve geographic problems in new environments and in new problem situations.

Thus to both ask and answer geographic questions, students should be provided with

o a template of the concepts used in geography (e.g., location, distribution, pattern, shape, association, hierarchy, network, etc., see Golledge (1996)) and with

o an outline of the processes involved in thinking geographically (e.g. observing, defining, interpolating, spatially associating, and so on, see Nyerges (1991)).

Together the template and the process assist not only in handling specific questions but also with linking questions that may not otherwise appear to be linked.

The ultimate aim is to develop an ability to understand what and where things are and how and why they are where they are.

The ability to state and answer geographic questions implies the existence of informed persons who

o can see meaning in the way things occur or are deliberately arranged in space,

o are capable of unpacking spatial relations between and among people, places, and environments,

o are capable of developing and using geographic skills and spatial abilities, and

o are capable of examining ecological, spatial and social perspectives to understand various life situations.

5. Relevance to GIS

GIS can help form, generate, and define geographic questions as well as help solve them.

By enabling representations of data to be displayed and visualized, GIS helps with identification and definition (i.e., generating "what" and "where" questions) as well as solving them by using various display modes.

Questions of association can be illustrated with overlay procedures.

Questions of change can be generated from sequential "snapshots" of locations, patterns and distributions.

A variety of analytical functions help solve "why" questions, and a selection of methods can be used to examine questions of methodology and process.

In particular, the instructor should provide:o examples of GIS functionalities and the questions they generateo examples of GIS methods and the problems to which they applyo examples of using GIS to change the naïve geographer into an experto examples of phrasing questions in different formats (verbal, graphic,

pictorial, mathematical).

6. Key References

Piper, K. (1976) Evaluation and the Social Sciences, National Committee on Social Science Teaching, Australian Government Planning Service, Canberra, ACT, Australia

Slater (1982) Learning through Geography, Heineman Educational Books, Ltd. London, UK

Timothy L. Nyerges (1991) Analytical Map Use. Cartography and GIS, 18

Reginald G. Golledge (1995) Spatial Primitives. In Nyerges, T.L., Mark, D.M., Laurini, R., and Egenhofer, M.J. (1995) Cognitive aspects of human-computer interaction for Geographic Information Systems. Proceedings of the NATO Advanced Research Workshop , Palma de Mallorca, Spain, March 20-25, 1994. NATO ASI Series D: Behavioural and Social Sciences - Volume 83. Dordrecht, The Netherlands: Kluwer Academic Publishers.

NCGE and National Geographic Society, Geography For Life. (1994)

7. Discussion and Exam Questions:

1. How does GIS help define and solve geographic questions?

2. How are spatial abilities used to interpret and solve geographic questions/problems?

3. Define the stages involved in generating and solving geographic questions.

4. Slater differentiates between "the Big Question" and others. Explain the nature of geographic questions in each of these categories.

5. Given that one can develop an understanding of the cognitive processes required to comprehend the world in spatial terms, how can GIS be used to relate that understanding to Places and Regions?

Evaluation

We are very interested in your comments and suggestions for improving this material. Please follow the link above to the evaluation form if you would like to contribute in this manner to this evolving project.

Citation

To reference this material use the appropriate variation of the following information:

by Timothy L. Nyerges and Reginald G. Golledge, NCGIA Core Curriculum in GIS, National Center for Geographic Information and Analysis, University of California, Santa Barbara, Unit 007, http://www.ncgia.ucsb.edu/giscc/units/u007/u007.html, posted November 12, 1997.

The correct URL for this page is: http://www.ncgia.ucsb.edu/giscc/units/u007/u007.html. Last revised: November 12, 1997.


NCGIA Core Curriculum in Geographic Information ScienceURL: "http://www.ncgia.ucsb.edu/giscc/units/u012/u012.html"

Unit 012 - Position on the Earthby Kenneth E. Foote, Department of Geography, University of Texas at Austin, USA

This unit is part of the NCGIA Core Curriculum in Geographic Information Science. These materials may be used for study, research, and education, but please credit the author Kenneth E. Foote, and the project,NCGIA Core Curriculum in GIScience. All commercial rights reserved. Copyright 1998.


Unit Topics

Five topics are highlighted in this section:o Unit 013 - Coordinate Systems Overview , by Peter Danao Unit 014 - Latitude and Longitude , by Anthony Kirvano Unit 015 - The Shape of the Earth , by Peter Danao Unit 016 - Discrete Georeferencing , by David Coweno Unit 017 - Global Positioning Systems Overview , by Peter Dana

These cover topics that are fundamental to understanding the systems of locational reference used in GIS.

The units have been written as overviews, but additional references and materials are provided for instructors wishing to extend their presentations of these important topics.

Intended Learning Outcomes of this Section

Determine location and calculate distances using global coordinate systems (latitude-longitude and UTM).

Determine location and calculate distances in the local coordinate system employed most commonly in the student's state, region, or nation.

Understand why different coordinate systems have been developed to record location.

Select a coordinate system suited to a particular GIS project. Explain how the shape of the earth is related to geographic position and to the

measurement of distance. Understand how geographic coordinates can be assigned to street address and

postal codes using discrete georeferencing. Identify the difficulties and errors that arise in discrete geocoding. Explain how a GPS receiver computes position and time from GPS signals and

list major types of error. State the methodological differences between single-user and differential GPS. Describe the practical differences between using GPS for low-precision and

high-precision positioning. See also the detailed learning outcomes listed below by unit.


Position on the Earth

1. The Importance of Position

Accurate referencing of geographic location is fundamental to all GIS.o The management, analysis, and reporting of all GIS data requires that it

be carefully referenced by position on the Earth's surface.o Mispositioned data can disrupt and even invalidate a GIS dataset and all

modeling based upon that dataset. Many different coordinate systems are used to record location.

o Some systems such as latitude and longitude are global systems that can be used to record position anywhere on the Earth's surface.

o Other systems are regional or local in coverage and intended to provide accurate positioning over smaller areas.

o Position is sometimes recorded in other ways, for instance by using postal codes and cadastral reference systems.

o The system of locational reference used in a particular GIS project will depend on the purpose of the project and how the positions of the source data have been recorded.

It is sometimes the case that the data needed for a particular GIS project will be recorded in two or more of these reference systems.

o Combining the information of these sources will require that positions be carefully converted, transformed, or projected from one system to another.

o This is a reason why GIS practitioners must usually be familiar with a variety of commonly used coordinate systems.

Geographic position is related to the shape of the Earth.o This shape is not a perfect sphere but rather an irregular ellipsoid.o Positions are sometimes reported in spherical units, but are more

commonly are adjusted to account for Earth shape using what are called geodetic datums.

Spherical distances and measurements differ from those that use geodetic datums to adjust for Earth shape.

o Accurate positioning requires knowledge of the datum used to construct a given coordinate system.

Transforming locations from one coordinate system to another will often also require shifting datums as well.

Phenomena whose positions are recorded by street address or postal code can also referenced using geographic coordinates.

o The process of matching street addresses and postal codes to geographic coordinate systems is called discrete georeferencing.

Precise positioning of natural and human phenomena can be a very demanding task.

o The level of precision with which position is recorded in a GIS dataset will vary from project to project.

Some engineering applications demand centimeter precision, some demographic and marketing applications require much lower precision to accomplish their objectives.

o High precision positioning usually requires the use of staff well trained in surveying, geodesy, and photogrammetry.

The Global Positioning System (GPS) is now used routinely for both low-precision and high-precision positioning.

o Low-precision GPS positioning can be attained by users with little knowledge of the underlying GPS technology and inexpensive equipment.

o High-precision GPS positioning requires both a thorough knowledge of the technology and more specialized equipment.

2. Overview of the Section Units

The units are intended to provide an overview to the most important issues in determining position.

These overviews still contain much technical information.o Lecturing from these units may occasionally require studying some of

the reference materials. Instructors are encouraged to adapt these materials to their audiences.

o Students often benefit from having these topics explained using local examples.

o Students often benefit from exercises and activities that require them to practice using different coordinate systems.

Instructors may find it useful to teach these units in conjunction with those on map projections and on uncertainty in spatial databases.

The contents and interrelationships of the units in this section are described below.

2.1. Unit 013 - Coordinate Systems Overview

This unit provides an overview of coordinate systems used for georeferencing, including:

o A description of basic coordinate systemso A description of the shape of the Eartho Some examples of global and regional systems used for precise

positioning, navigation, and geographic information systems The overview discusses the rationale behind these systems and how they are

used After learning the material covered in this unit, students should be able to:

o List the major global georeferencing systemso Explain how the UTM georeferencing system is organizedo Locate a given local landmark in three or more global or regional

coordinate systemso Express the location of the student's home in UTM and one regional

coordinate systemo Identify the georeferencing system used most widely in the student's

locality.o Differentiate between different global systems of georeferencing

including UTM, MGRS, and GEOREF systems.o Collect examples of regional and local coordinate systems employed by

nations or states not mentioned in the text.o Find and plot one example of a metes-and-bounds surveyo Plan a regional GIS project that spans two or more UTM or SPC zones.

2.2. Unit 014 - Latitude and Longitude

This unit focuses on the most widely used global reference system, latitude and longitude.

It defines, explains, and illustrates:o Earth rotation, the North and South Poles, and the Equatoro Parallels of latitude and meridians of longitudeo Determination of north or south position with latitudeo The use of longitude to determine east or west positiono The measurement of latitude and longitude with degrees, minutes, and

seconds After learning the material covered in this unit, students should gain an

appreciation for:o The relationship between plane and earth coordinate geometrieso The importance of the earth's rotation and poles to measurement and

point locationo The use of latitude and longitude to determine locations on the earth's

surfaceo The differences and relationships between latitude and longitudeo Using latitude and longitude to measure distances

2.3. Unit 015 - The Shape of the Earth

This unit focuses on the shape of the Earth, and how this shape is related to location.

The unit provides an overview of the following concepts:

o Geodetic datumso Geometric Earth modelso Reference ellipsoidso Earth surfaces

After learning the material covered in this unit, students should gain an appreciation for:

o The various methods of describing the size and shape of the eartho The evolution of a flat earth model into an accurate spherical

representation.

2.4. Unit 016 - Discrete Georeferencing

GIS often must assign geographic coordinates to data recorded by street address or postal code using discrete georeferencing.

This unit provides an overview of discrete georeferencing, including:o Description of how georeferencing is used to create GIS databaseso Applications that rely on georeferencingo The level of geographic resolution possible for various alternatives of

georeferencingo Sources of base maps for georeferencingo Software for georeferencing address fileso Problems associated with handling addresseso Internet resources for georeferencing

After learning the material covered in this unit, students should understand:o The importance of georeferencing as a way to create GIS databaseso The limitations of the approach and the benefits of certain alternativeso The mechanics of how to use GIS software to perform georeferencing

taskso Sources of software and data for performing geocoding operations

2.5. Unit 017 - Global Positioning Systems Overview

The Global Positioning System (GPS) is now widely used for both low-precision and high-precision positioning.

This unit provides an overview of the GPS including:o A description of the space, control and user components of the system.o A description of the basic services provided by GPS.o A discussion of position and time determination from GPS signals.o A discussion of GPS error sources and methods for overcoming some

GPS errors. The overview discusses GPS project planning and costs.

The overview does not discuss details of GPS signals and data formats, but does provide references to relevant sources.

After learning the material covered in this unit, students should be able to:o List the major GPS segments as defined by the Department of Defense.o Explain how a GPS receiver computes position and time from GPS

signals.o Describe the major error sources for GPS positioning projects.o Explain the various forms of Differential GPS.o Propose suitable equipment and processes for various levels of

positioning accuracy.

Unit 013 - Coordinate Systems Overviewby Peter H. Dana, Department of Geography, University of Texas at Austin, USA

This section was edited by Kenneth Foote, Department of Geography, University of Texas Austin.

This unit is part of the NCGIA Core Curriculum in Geographic Information Science. These materials may be used for study, research, and education, but please credit the author, Peter H. Dana, and the project,NCGIA Core Curriculum in GIScience. All commercial rights reserved. Copyright 1997 by Peter H. Dana.


Advanced Organizer


This unit provides an overview of coordinate systems used for georeferencing, including:

o a description of basic coordinate systemso a description of the shape of the Eartho some examples of global and regional systems used for precise

positioning, navigation, and geographic information systems

http://www.ncgia.ucsb.edu/education/curricula/giscc/units/u013/u013.html#evaluation

http://www.ncgia.ucsb.edu/giscc

The overview discusses the rationale behind these systems and how they are used

Learning Outcomes

After learning the material covered in this unit, students should be able to:o List the major global georeferencing systemso Explain how the UTM georeferencing system is organizedo Locate a given local landmark in three or more global or regional

coordinate systemso Express the location of the student's home in UTM and one regional

coordinate systemo Identify the georeferencing system used most widely in the student's

locality.o Differentiate between different global systems of georeferencing

including UTM, MGRS, and GEOREF systems.o Collect examples of regional and local coordinate systems employed by

nations or states not mentioned in the text.o Find and plot one example of a metes-and-bounds surveyo Plan a regional GIS project that spans two or more UTM or SPC zones.


Instructors' Notes


Unit 013 - Coordinate Systems Overview

1. Basic Coordinate Systems

There are many basic coordinate systems familiar to students of geometry and trigonometry.

o These systems can represent points in two-dimensional or three-dimensional space.

Ren� Decartes (1596-1650) introduced systems of coordinates based on orthogonal (right angle) axes.

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o These two and three-dimensional systems used in analytic geometry are often referred to as Cartesian systems.

Similar systems based on angles from baselines are often referred to as polar systems.

1.1. Plane Coordinate Systems

Two-dimensional coordinate systems are defined with respect to a single plane, as demonstrated in the following figures:

o Figure 1. A Point Described by Cartesian Coordinates in a Planeo Figure 2. A Line Defined by Two Points in a Planeo Figure 3. Distance Between Two points (Line Length) from the formula

of Pythagoraso Figure 4. A Point Described by Polar Coordinates in a Planeo Figure 5. Conversion of Polar to Cartesian Coordinates in a Plane

1.2. Three-Dimensional Systems

Three-dimensional coordinate systems can be defined with respect to two orthogonal planes.

o Figure 6. A Point Described by Three-Dimensional Cartesian Coordinateso Figure 7. A Point Described by Three-Dimensional Polar Coordinateso Figure 8. Conversion of Three-Dimensional Polar to Three Dimensional

Cartesian Coordinates

2. Earth-Based Locational Reference Systems

Reference systems and map projections extend the ideas of Cartesian and polar coordinate systems over all or part of the earth.

o Map projections portray the nearly spherical earth in a two-dimensional representation.

Earth-based reference systems are based on various models for the size and shape of the earth.

o Earth shapes are represented in many systems by a sphereo However, precise positioning reference systems are based on

an ellipsoidal earth and complex gravity models.

2.1. Reference Ellipsoids

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Ellipsoidal earth models are required for precise distance and direction measurement over long distances.

o Ellipsoidal models account for the slight flattening of the earth at the poles. This flattening of the earth's surface results at the poles in about a twenty kilometer difference between an average spherical radius and the measured polar radius of the earth.

o The best ellipsoidal models can represent the shape of the earth over the smoothed, averaged sea-surface to within about one-hundred meters.

Reference ellipsoids are defined by either:o semi-major (equatorial radius) and semi-minor (polar radius) axes, oro the relationship between the semi-major axis and the flattening of the

ellipsoid (expressed as its eccentricity).o Figure 9. Reference Ellipsoid Parameters

Many reference ellipsoids are in use by different nations and agencies.o Table 1. Selected Reference Ellipsoids

Reference ellipsoids are identified by a name and often by a yearo for example, the Clarke 1866 ellipsoid is different from the Clarke 1858

and the Clarke 1880 ellipsoids.

2.2. Geodetic Datums

Precise positioning must also account for irregularities in the earth's surface due to factors in addition to polar flattening.

Topographic and sea-level models attempt to model the physical variations of the surface:

o The topographic surface of the earth is the actual surface of the land and sea at some moment in time.

Aircraft navigators have a special interest in maintaining a positive height vector above this surface.

o Sea level can be thought of as the average surface of the oceans, though its true definition is far more complex.

Specific methods for determining sea level and the temporal spans used in these calculations vary considerably.

Tidal forces and gravity differences from location to location cause even this smoothed surface to vary over the globe by hundreds of meters.

Gravity models and geoids are used to represent local variations in gravity that change the local definition of a level surface

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o Gravity models attempt to describe in detail the variations in the gravity field.

The importance of this effort is related to the idea of leveling. Plane and geodetic surveying uses the idea of a plane perpendicular to the gravity surface of the earth which is the direction perpendicular to a plumb bob pointing toward the center of mass of the earth.

Local variations in gravity, caused by variations in the earth's core and surface materials, cause this gravity surface to be irregular.

o Geoid models attempt to represent the surface of the entire earth over both land and ocean as though the surface resulted from gravity alone.

Geodetic datums define reference systems that describe the size and shape of the earth based on these various models.

o While cartography, surveying, navigation, and astronomy all make use of geodetic datums, they are the central concern of the science of geodesy.

Hundreds of different datums have been used to frame position descriptions since the first estimates of the earth's size were made by the ancient greeks.

o Datums have evolved from those describing a spherical earth to ellipsoidal models derived from years of satellite measurements.

o Modern geodetic datums range from flat-earth models, used for plane surveying to complex models, used for international applications, which

completely describe the size, shape, orientation, gravity field, and angular velocity of the earth.

Different nations and international agencies use different datums as the basis for coordinate systems in geographic information systems, precise positioning systems, and navigation systems.

o In the United States, this work is the responsibility of the National Geodetic Survey (http://www.ngs.noaa.gov/).

o Links to some of the NGS's counterparts in other nations are listed below inSection 7.2 (Web References).

Linking geodetic coordinates to the wrong datum can result in position errors of hundreds of meters.

o The diversity of datums in use today and the technological advancements that have made possible global positioning measurements with sub-meter accuracies requires careful datum selection and careful conversion between coordinates in different datums.

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For the purposes of this unit, reference system can be divided into two groups:.

o Global systems can refer to positions over much of the Earth.o Regional systems have been defined for many specific areas, often

covering national, state, or provincial areas.

3. Global Systems

3.1. Latitude, Longitude, Height

The most commonly used coordinate system today is the latitude, longitude, and height system.

The Prime Meridian and the Equator are the reference planes used to define latitude and longitude.

o Figure 10 . Equator and Prime Meridian There are several ways to define these terms precisely. From the geodetic

perspective these are:o The geodetic latitude of a point is the angle between the equatorial

plane and a line normal to the reference ellipsoid.o The geodetic longitude of a point is the angle between a reference

plane and a plane passing through the point, both planes being perpendicular to the equatorial plane.

o The geodetic height at a point is the distance from the reference ellipsoid to the point in a direction normal to the ellipsoid.

o Figure 11 . Geodetic Latitude, Longitude, and Height

3.2. ECEF X, Y, Z

Earth Centered, Earth Fixed (ECEF) Cartesian coordinates can also be used to define three dimensional positions.

ECEF X, Y, and Z Cartesian coordinates define three dimensional positions with respect to the center of mass of the reference ellipsoid.

o The Z-axis points from the center toward the North Pole.o The X-axis is the line at the intersection of the plane defined by the

prime meridian and the equatorial plane.o The Y-axis is defined by the intersection of a plane rotated 90� east of

the prime meridian and the equatorial plane.o Figure 12. ECEF X, Y, and Z




o Table 2. ECEF X, Y, Z Coordinates Example

3.3. Universal Transverse Mercator (UTM)

Universal Transverse Mercator (UTM) coordinates define two dimensional, horizontal, positions.

Each UTM zone is identified by a numbero UTM zone numbers designate individual 6� wide longitudinal strips

extending from 80� South latitude to 84� North latitude.o (Military UTM coordinate systems also use a character to designate 8�

zones extending north and south from the equator, see below).o Figure 13 . UTM Zones

Each zone has a central meridian.o For example, Zone 14 has a central meridian of 99� west longitude.

The zone extends from 96 to 102� west longitude.o Figure 14. UTM Zone 14

Locations within a zone are measured in meters eastward from the central meridian and northward from the equator. However,

o Eastings increase eastward from the central meridian which is given a falseeasting of 500 km so that only positive eastings are measured anywhere in the zone.

o Northings increase northward from the equator with the equator's value differing in each hemisphere

in the Northern Hemisphere, the Equator has a northing of 0 for Southern Hemisphere locations, the Equator is given a false

northing of 10,000 kmo Figure 15. UTM Zone 14 Example Detailo Table 3. UTM Coordinate Example

3.4. Military Grid Reference System (MGRS)

The Military Grid Reference System (MGRS) is an extension of the UTM system.

A UTM zone number and an additional zone character are used to identify areas 6� in east-west extent and 8� in north-south extent.

o A few special UTM zones do not match the standard configuration (seeFigure 13)






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between 0� and 42� east longitude, above 72� north latitude in the area of the Greenland and Barents Seas, and the Arctic Ocean.

in zones 31 and 32 between 56� and 64� north latitude including portions of the North Sea and Norway.

UTM zone number and character are followed by two characters designating the eastings and northings of 100 km square grid cells.

o Starting eastward from the 180� meridian, the characters A to Z are assigned consecutively to up to 24 strips covering 18� of longitude (characters I and O are omitted to eliminate the possibility of confusion with the numerals 1 and 0). The sequence begins again every 18�.

o From the equator northward, the characters A to V (omitting characters I and O) are used to sequentially identify 100 km squares, repeating the sequence every 2,000 km.

for odd numbered UTM easting zones, northing designators normally begin with 'A' at the equator

for even numbered UTM easting zones, the northing designators are offset by five characters, starting at the equator with 'F'.

South of the equator, the characters continue the pattern set north of the equator.

Complicating the system, ellipsoid junctions ("spheroid junctions" in the terminology of MGRS) require a shift of 10 characters in the northing 100 km grid square designators. Different geodetic datums using different reference ellipsoids use different starting row offset numbers to accomplish this.

o Figure 16. Military Grid Reference System For a full MGRS location, UTM zone number and character and the two grid

square designators are followed by an even number of digits representing more precise easting and northing values.

o 2 digits give a coordinate precision of 10 km.o 10 digits give a coordinate precision of 1 m.o Table 4. MGRS Example

MGRS and UTM systems are often employed in products produced by the US National Imagery and Mapping Agency (http://www.nima.mil/), formerly the Defense Mapping Agency.

3.5. World Geographic Reference System (GEOREF)

The World Geographic Reference System is used for aircraft navigation.

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GEOREF is based on latitude and longitude. The globe is divided into twelve bands of latitude and twenty-four zones of

longitude, each 15� in extent.o Figure 17 . World Geographic Reference System Index

These 15� areas are further divided into one degree units identified by 15 characters.

o Figure 18. GEOREF 1� Grido Table 5. GEOREF Example

4. Regional Systems

Several different systems are used regionally to identify geographic location Some of these are true coordinate systems, such as those based on UTM and

UPS systems Others, such as the metes and bounds and Public Land Survey systems

describe below, simply partition space

4.1. Transverse Mercator Grid Systems

Many nations have defined grid systems based on Transverse Mercator coordinates that cover their territory.

4.1.1. An example - the British National Grid (BNG)

The British National Grid (BNG) is based on the National Grid System of England, administered by the British Ordnance Survey (http://www.ordsvy.gov.uk/)

The BNG has been based on a Transverse Mercator projection since the 1920s.o The modern BNG is based on the Ordnance Survey of Great Britain

Datum 1936. The true origin of the system is at 49� north latitude and 2 degrees west

longitude.o The false origin is 400 km west and 100 km north.

Scale factor at the central meridian is 0.9996012717. The first BNG designator defines a 500 km square. The second designator defines a 100 km square.

o Figure 19 . British National Grid 100 km Squares


http://www.ordsvy.gov.uk/




The remaining digits define 10 km, 1 km, 100 m, 10 m, and 1 m eastings and northings.

o Table 6 . British National Grid Example

4.2. Universal Polar Stereographic (UPS)

The Universal Polar Stereographic (UPS) projection is defined above 84� north latitude and south of 80� south latitude.

The eastings and northings are computed using a polar aspect stereographic projection.

Zones are computed using a different character set for south and north Polar regions.

Figure 20 . North Polar Area UPS Grido Table 7 . North Polar UPS Example

Figure 21 . South Polar Area UPS Grido Table 8 . South Polar UPS Example

4.3. State Plane Coordinates (SPC)

State plane systems were developed in order to provide local reference systems that were tied to a national datum.

In the United States, the State Plane System 1927 was developed in the 1930s and was based on the North American Datum 1927 (NAD-27).

o NAD-27 coordinates are in English units (feet).o Figure 22 . NAD-27 State Plane Coordinate Example

The State Plane System 1983 is based on the North American Datum 1983 (NAD-83).

o NAD-83 coordinates are metric.o Table 9 . NAD-83 State Plane Coordinate Exampleo While the NAD-27 State Plane System has been superceded by the

NAD-83 System, maps in NAD-27 coordinates are still in use. Most USGS 7.5 Minute Quadrangles show several coordinate system grids

including latitude and longitude, UTM kilometer tic marks, and applicable State Plane coordinates.

o Figure 23 . Three Coordinate Systems on the Austin, East USGS 7.5' Quadrangle

Each state has its own State Plane system with specific parameters and projections.









o Software is available for easy conversion to and from latitude and longitude.

o A popular public domain software package, CORPSCON is maintained by the US Army Corps of Engineers

Some smaller states use a single state plane zone while larger states are divided into several zones.

o State plane zone boundaries often follow county boundaries.o Figure 24 . State Plane Zone Example

Two projections are used in all State Plane systems, with one exception:o Lambert Conformal Conic projections are used for regions with a larger

east-west than north-south extent. examples are Nebraska and North Carolina

o Transverse Mercator projections are used for regions with a larger north-south extent.

examples are New Hampshire and Illinoiso Some states use both projections

in Florida, the Lambert Conformal Conic projection is used for the North zone while the Transverse Mercator projection is used for the East and West zones.

o The exception is one State Plane zone in Alaska which uses an Oblique Mercator projection for a thin diagonal area.

Figure 25 . Alaska State Plane Zone 5001

4.4. Public Land Rectangular Surveys (USPLS)

Public Land Rectangular Surveys have been used since the 1790s to identify public lands in the United States.(USPLS = US Public Land Survey)

o The system is based on principal meridians and baselines. Townships, square with six miles on each side, are numbered with reference

to a baseline and principal meridian.o actually, few townships are truly square due to convergence of the

meridians. Ranges are the distances and directions from baseline and meridian expressed

in numbers of townships. Every four townships, a new baseline is established so that orthogonal

meridians can remain north oriented.o Figure 26 . U.S. Rectangular Survey

Sections, approximately one mile square, are numbered from 1 to 36 within a township.




http://www.usace.army.mil/

http://www.tec.army.mil/TD/corpscon.html

o Figure 27 . Township Sectionso Sections are divided into quarter sections.o Quarter sections are divided into 40-acre, quarter-quarter sections.o Quarter-quarter sections are sometimes divided into 10-acre areas.o Figure 28 . Subdivided Sectiono Fractional units of section quarters, designated as numbered lots, often

result from irregular claim boundaries, rivers, lakes, etc. Abbreviations are used for Township (T or Tps), Ranges (R or Rs), Sections (Sec

or Secs), and directions (N, E, S, W, NE, etc.).o Table 10 . A Township and Range Property Description

4.5. Metes and Bounds

Metes and Bounds identify the boundaries of land parcels by describing lengths and directions of a sequence of lines forming the property boundary.

o Lines are described with respect to natural or artificial monuments and to baselines drawn from these monuments.

The metes and bounds survey is based on a point of beginning, an established monument.

o Line lengths are measured along a horizontal level plane.o Directions are bearing angles measured with respect to the previous

line in the survey.o Table 11 . Metes and Bounds Exampleo Figure 28a . Metes and Bounds graphic

Metes and bounds descriptions are also referred to as COGO (CoordinateGeometry) when used in GIS and CAD systems

5. Summary

This overview has introduced a number of global and regional coordinate systems. A single point on the Earth can be described in a variety of systems. Each GIS project may require the use of a specific locational reference system. It is important to be aware of the variety of systems in use.

As an example of a point that could be referred to by a number of different system, one of the horizontal control monuments used in the survey network maintained by the National Geodetic Survey (the star in the hand of the statue

http://www.ncgia.ucsb.edu/education/curricula/giscc/units/u013/figures/metes.jpg





of the Goddess of Liberty on top of the state capitol building in Austin, Texas) has been used throughout this overview.

o Figure 29 . The Texas Capitol Buildingo Figure 30 . The Star in the Hand of The Goddess of Liberty

This horizontal control monument can be described by many different locational reference systems.

o Table 12 . One Location Described by a Variety of Systems

6. Review and Study Questions

6.1. Essay and Short Answer Questions

In what ways does the long and widespread use of SPC, UTM, COGO, and USPLS reference systems limit the possibility of building regional and state-wide GIS?

What is metes and bounds surveying and how is it used to measure and record land records?

The US Public Land Survey is a method of cadastral partitioning. How has it influenced the appearance of the American landscape and why?

What is the rationale behind both the State Plane Coordinate and Universal Transverse Mercator coordinate systems?

From the standpoint of locational reference systems (SPC and UTM) and methods of cadastral partitioning (USPLS, metes and bounds, etc.), why is Texas such an unusual state?

Describe the Township and Range land surveying system. Use a diagram. What is a false origin? In practice, why are they always placed outside of the

map zone being used? In a state of Texas's size, why can't SPC or UTM coordinates be used for

mapping and GIS projects that span the entire state? Why was the State Plane Coordinate System such an important advance for

mapping in the US?

6.2. Multiple-choice questions

Choose the best or most appropriate answer(s) to the question.

Which of the following statements are true of both SPC and UTM coordinate systems?




1. both SPC and UTM are for mapping in the US2. both SPC and UTM employ conformal, equidistant projections3. within the US both systems yield horizontal coordinates of equal

precision4. UTM zones correspond to state boundaries, whereas SPC zone are

aligned with county boundaries

Which system incorporates a false origin to measure position within a Cartesian grid?

1. metes and bounds2. State Plane Coordinate System (SPC)3. Universal Transverse Mercator (UTM)4. Township and Range5. long lots

Which of the following are true about the SPC?1. accuracy is 1 part in 100002. the system is best used in regional and statewide GIS projects3. city governments resist using the SPC because of cost4. both A and B5. none of the above

7. Reference Materials

7.1. Print References

Bugayevskiy, Lev M. and John P. Snyder. 1995. Map Projections: A Reference Manual. London: Taylor and Francis. This book contains a general exposition on map projection theory followed by sections on particular types of projection. Projections are classified by those whose parallels are straight, in the shape of concentric circles, or in the shape on non-concentric circles. Other types map projections and current map projection research are discussed. This is an excellent resource especially when paired with Snyder's Map Projections 1987.

Clarke, Keith C. 1995. Analytical and Computer Cartography, 2nd ed.Englewood Cliffs, NJ: Prentice Hall.

This book contains descriptions of most coordinate systems used in GIS along with enough technical details (including source code examples and a diskette) to work out many coordinate system conversions including computer raster graphic transformations not included in many other books on map projections.

Defense Mapping Agency. 1977. The American Practical Navigator: Publication No. 9, Defense Mapping Agency Hydrographic Center. A venerable reference work containing many practical details for using maps and navigation systems. While primarily useful for working with nautical charts, the book contains sections on numerous navigation aids, from sextants to GPS.

Defense Mapping Agency. 1991. World Geodetic System 1984 (WGS 84) - Its Definition and Relationships with Local Geodetic Systems, 2nd Edition. Washington, DC: Defense Mapping Agency (DoD). The primary source for WGS-84 information, including lists of reference ellipsoids, geodetic datums, and the simple three-parameter datum shift values required for datum transformation approximations.

Laurila, Simo H. 1976. Electronic Surveying and Navigation. New York: John Wiley & Sons. An excellent source for geodetic formulas, including details on latitude, longitude, height systems, rectangular coordinate systems and ellipsoidal geodesics. The book, while somewhat dated now, provides a good background on many surveying and navigation systems in use today.

Muehrcke, P.C and Juliana O. Muehrcke. 1992. Map Use. Madison, WI: JP Publications. While not a technical manual for mapping transformations, the book has very clear descriptions of most coordinate systems as well as discussions of many more detailed GIS issues relating to terrain surfaces and statistical evaluations.

Maling, D.H. 1992. Coordinate systems and map projections. 2nd ed. New York: Pergamon Press. A reference manual containing algorithms and formulas for conversion between different coordinate systems and map projections.

Robinson, Arthur H., Joel L. Morrison, Phillip C. Muehrcke, A. Jon Kimerling, and Stephen C. Guptill. 1995. Elements of Cartography. 6th ed. New York: John Wiley and Sons, 41-58, 91-111. A book that has served as the basis for cartography courses for more than 40

years. An indispensable reference book covering all phases of map making and map reading.

Snyder, John P. 1987. Map Projections: A Working Manual. Washington, DC: US Government Printing Office. The best single reference for details on map projection methods, the book includes numerical examples for help in producing map projection code.

US Army. 1967. TM 5-241-1 Grids and Grid References. Washington, DC: Department of the Army. A complete description of MGRS and UTM, including maps of the world with the MGRS preferred "spheroids" and MGRS row offsets. This old edition is out of print and does not contain WGS-84-based MGRS details.

7.2. Web References

7.2.1. US Federal Agencies

US Army Corps of Engineers, http://www.tec.army.mil/o maintains the CORPSCON program which is described

athttp://crunch.tec.army.mil/software/corpscon/corpscon.html US Geological Survey, http://www.usgs.gov/

o EROS Data Center, http://edcwww.cr.usgs.gov/o National Mapping Division, http://www-nmd.usgs.gov/o Global Land Information System, http://edcwww.cr.usgs.gov/webglis/

US National Geodetic Survey, http://www.ngs.noaa.gov/o Geodetic Control

Subcommittee,http://www.ngs.noaa.gov/FGCS/index.htmo a set of links to programs for geodetic adjustments and coordinate

system translations is maintained by the NGS athttp://www.ngs.noaa.gov/PC_PROD/pc_prod.html

US National Imagery and Mapping Agency (NIMA), http://www.nima.mil/

7.2.2. Non-US Federal Agencies

Australian Surveying and Land Information Group (AUSLIG),http://www.auslig.gov.au/index.htm

o AUSLIG Geodesy Division,http://www.auslig.gov.au/geodesy/newhome.htm

British Geological Survey, http://www.bgs.ac.uk/ Geomatics Canada/G�omatique Canada

http://www.bgs.ac.uk/

http://www.auslig.gov.au/geodesy/newhome.htm

http://www.auslig.gov.au/index.htm

http://www.nima.mil/

http://www.ngs.noaa.gov/PC_PROD/pc_prod.html

http://www.ngs.noaa.gov/FGCS/index.htm

http://www.ngs.noaa.gov/

http://edcwww.cr.usgs.gov/webglis/

http://www-nmd.usgs.gov/

http://edcwww.cr.usgs.gov/

http://www.usgs.gov/

http://crunch.tec.army.mil/software/corpscon/corpscon.html

http://www.tec.army.mil/

o National Atlas Information Service, http://www-nais.ccm.emr.ca/o Geodetic Survey of Canada/Division des lev�s

g�od�siques,http://www.geod.nrcan.gc.ca/ Geographical Survey Institute of

Japan, http://www.gsi-mc.go.jp/ENGLISH/index.html Institut G�ographique National (France), http://www.ign.fr/ National Survey and Cadastre (Denmark), http://www.kms.dk/index_en.html Ordnance Survey (United Kingdom), http://www.ordsvy.gov.uk/ Ordnance Survey of Northern Ireland, http://www.osni.gov.uk/ Sistema Nactional de Informa��o Geogr�phica

(Portugal),http://www.cnig.pt/index_I.html Statens Kartverk (Norway), http://www.statkart.no/

7.2.3. Other relevant webpages

The following are related sections by the same author in The Geographer's Craft Project at the University of Texas Austin:

o Dana, Peter H. 1995. Geodetic Datum Overview,http://www.colorado.edu/geography/gcraft/notes/datum/datum_f.html

o Dana, Peter H. 1995. Coordinate Systems Overview,http://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys_f.html

o Dana, Peter H. 1995. Map Projections Overview,http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj_f.html

Evaluation


http://www.ncgia.ucsb.edu/education/curricula/giscc/units/evaluation/password_ck.html

http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj_f.html

http://www.colorado.edu/geography/gcraft/notes/mapproj/mapproj_f.html

http://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys_f.html

http://www.colorado.edu/geography/gcraft/notes/coordsys/coordsys_f.html

http://www.colorado.edu/geography/gcraft/notes/datum/datum_f.html

http://www.colorado.edu/geography/gcraft/notes/datum/datum_f.html

http://www.statkart.no/

http://www.cnig.pt/index_I.html

http://www.osni.gov.uk/

http://www.ordsvy.gov.uk/

http://www.kms.dk/index_en.html

http://www.ign.fr/

http://www.gsi-mc.go.jp/ENGLISH/index.html

http://www.geod.nrcan.gc.ca/

http://www-nais.ccm.emr.ca/

Citation

To reference this material use the appropriate variation of the following format:

Dana, Peter H. (1997) Coordinate Systems Overview, NCGIA Core Curriculum in GIScience, http://www.ncgia.ucsb.edu/giscc/units/u013/u013.html, posted (today).

http://www.ncgia.ucsb.edu/giscc/units/u013/u013.html

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