Lecture 4 Data
Dec 25, 2015
Why GIS?
Ask questions Solve a problem Support a decision Make Maps Involve others, share data, procedures, ideas
What is a GIS?
GISs are simultaneously the telescope, the
microscope, the computer, and the Xerox
machine of regional analysis and synthesis
of spatial data. (Ron Abler, 1988)
Definition 1: A GIS is a toolbox "a powerful set of tools for storing and
retrieving at will, transforming and displaying spatial data from the real world for a particular set of purposes"
(Burrough, 1986, p. 6).
"automated systems for the capture, storage, retrieval, analysis, and display of spatial data." (Clarke, 1995, p. 13).
Definition 2: A GIS is an information system "An information system that is designed to
work with data referenced by spatial or geographic coordinates. In other words, a GIS is both a database system with specific capabilities for spatially-referenced data, as well as a set of operations for working with the data" (Star and Estes, 1990, p. 2).
Definition 3: GIS is an approach to science Geographic Information Science is research
both on and with GIS.
"the generic issues that surround the use of GIS technology, impede its successful implementation, or emerge from an understanding of its potential capabilities."
(Goodchild, 1992)
Definition 4: GIS plays a role in society
Nick Chrisman (1999) “organized activity by which people measure and represent geographic phenomena, and then transform these representations into other forms while interacting with social structures.”
Hardware
Computer, CPU, memory, and monitor Modem and internet connection Data collection devices, GPS, handheld data Scanner or digitizing table Plotter and printer Web Server
Software
GIS software – range of functions Software extensions – add functions Data viewers – least functionality Single purpose software – make parcel maps Software for the web – ATM, House locators Non-GIS software - database, statistics,
image processing
Procedures
Data input – paper maps, GPS, images Data management - edit and quality Query - Asking map questions Analysis - Spatial, tabular and statistical
analysis Map overlay Distance calculations
Data output - Map making, on screen, paper, internet
People with spatial knowledge Data entry Data quality Analyst Developer / Programmer Database manager Web developer Project manager GIS managerwww.gjc.org - GIS jobs listing
Data storage formats Maps and layers
Mxd lyr
Vector Geodatabase, shapefile, coverage DXF, DWG DGN
Raster GRID, sid, img, gif, jpeg
Tables Geodatabase, dbf,
3D TIN format
Vector data Point - x, y Line - list of x, y coordinates Polygon - list of lines that form a closed area
Points
4753456 6234124753436 6234244753462 6234784753432 6234824753405 6234294753401 6235084753462 6235554753398 623634
Lines Polygons
Feature class Group of points, lines, or polygons Has a theme-rivers, streets, cities, lakes, states… Makes a layer
Point feature class
Line feature class
Polygon feature class
Layer files File for one layer, stores its symbology .lyr extension, streets.lyr Add to any map or share with friends No data
Pointer to data Symbols
What is a database Storage format Container for tables of data Allows queries The sales table contains five tables