CFR 250/590 Introduction to GIS © Phil Hurvitz, 1999-2000intro_gis.ppt 1 Introduction to GIS Spatial (coordinate) data model Relational (tabular) data.

© Phil Hurvitz, 1999-2000

CFR 250/590 Introduction to GIS

intro_gis.ppt 1

Introduction to GIS

• Spatial (coordinate) data model

• Relational (tabular) data model

• Scale issues

• Sample data_

Overview



intro_gis.ppt 2

Spatial Data Model

• GIS are driven by spatial data

• 2 basic spatial data models exist

• vector• points• lines • polygons

• raster• grid cells (images, bitmaps, DEMs)

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intro_gis.ppt 3

Vector Data Model

• Characteristics of the vector data model:

• Features positioned accurately

• Shape of features represented correctly

• Features represented discretely (no fuzzy boundaries)

• Complex data structure (especially for polygons)_



intro_gis.ppt 4

Vector Data Model

Points: represent discrete point features



intro_gis.ppt 5

Vector Data Model

Lines: represent linear features



intro_gis.ppt 6

Vector Data Model

Lines: represent linear features

• Lines start and end at nodes• line #1 goes from node #2 to node #1

• Vertices determine shape of line_



intro_gis.ppt 7

Vector Data Model

Polygons: represent bounded areas



intro_gis.ppt 8

Vector Data Model


• Polygon #2 is bounded by lines 1 & 2• Line 2 has polygon 1 on left and polygon 2 on right

_



intro_gis.ppt 9

Vector Data Model

• complex data model• “arc/node topology”

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intro_gis.ppt 10

Vector Data Model

Types (formats) of vector data available in ArcView

• ArcView shapefiles

• ArcInfo coverages and libraries

• CAD files (AutoCAD DWG, DXF;Microstation DGN)

• StreetMap files

• Spatial Database Engine (SDE) data

• ASCII point coordinate data_



intro_gis.ppt 11

Vector Data Model

• A relatively new vector data format

• Preferred in ArcView• Draws fast• Fully editable in ArcView

• Simple in structure

• Does not use arc-node topology• “Connected” lines do not necessarily share a common node• Adjacent polygons do not share common bounding arcs• Data sets are either point or line or polygon

_

ArcView shapefiles



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Vector Data Model

• A commonly found format

• Data model more complex

• Draws more slowly in ArcView

• Coordinate data not editable in ArcView

• Can be used in both ArcView and ArcInfo

• Polymorphic

• Problematic file structure (more on this later in the term)_

ArcInfo coverages



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Vector Data Model

• CAD data are very common (industry standard)

• DXF, DWG, and DGN formats supported in ArcView

• Coordinate data not editable in ArcView

• Frequently contain “sloppy” data• No enforced topology rules• Gaps in data

• Frequently contain little or no useful attribute data_

AutoCAD & Microstation CAD drawing data



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Vector Data Model

• Easy to obtain from a variety of sources• GPS• Traverse• Direct reading from maps

• OS, architecture, and application independent

ASCII coordinate data



intro_gis.ppt 15

Raster Data Model

• Rectangular grid of square cells

• Shape of features generalized by cells

• Continuous (surface) data represented easily

• Simple data structure_

Characteristics of the raster data model:



intro_gis.ppt 16

Raster Data Model

• Wind speed

• Elevation, slope, aspect

• Chemical concentration

• Likelihood of existence of a certain species

• Electromagnetic reflectance (photographic or satellite imagery)_

Raster data are good at representing continuous phenomena



intro_gis.ppt 17

Raster Data Model

• origin is set explicitly

• cell size is known

• cell references (row/column locations)are known

• cell values are referencedto row/column location

• values represent numerical phenomena orindex codes for non-numerical phenomena_

Raster spatial data model



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Raster Data Model

• digital orthophoto

• digital elevation model (DEM)_

A few different types of raster data



intro_gis.ppt 19

• The “where” of GIS is determined by coordinate (map) data structures, but …

• The “what” of GIS is determined by tabular (relational database) data structures

• Thus, tabular data are just as important as coordinate data_

Relational Database Model & Attribute Data Structures



intro_gis.ppt 20


• Tables are composed of:

• fields

and

• records_

Attribute data are stored in database tables.



intro_gis.ppt 21


• dBase

• rBase

• Access

• Excel (database functionality)

• Oracle, INFORMIX, INGRES, SQL Server

• INFO (in ArcInfo)_

You may already be familiar with relational databases



intro_gis.ppt 22


• tables are stored on the disk as

• .dbf,

• .txt, or

• in INFO directories_

ArcView uses tabular data formats from dBase, ASCII text, and INFO files



intro_gis.ppt 23


Tables can be linked and joined (“related”) by use of common values in fields



intro_gis.ppt 24


• Vector• point attribute tables• polygon attribute• line attribute

• node attribute* • text attribute*• route & event tables*

* in ArcInfo coverage data only

Different types of attribute tables in ArcView

• Raster• value attribute

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intro_gis.ppt 25


Relationship between tabular and map data

• one-to-one between features and records_



intro_gis.ppt 26

Scale Issues

Be aware of:

• Data’s source scale

• Mixing data from different source scales

• Appropriateness of output scale_

Scale of data plays an important role, and frequently causes problems



intro_gis.ppt 27

Scale Issues

• A 1/40th in line on a 1:24,000 scale map is 50 ft on the ground

50' * * 0.025" 12"1'

1"24,000"

• A .30 mm line on a 1:200,000 scale map is almost 2,000 ft on the ground_

1,969' * * * * mm 0.30 12"1'

2.54cm1"

mm 101cm

12,000,000

Map measurement and true ground measurement



intro_gis.ppt 28

Scale Issues

• 1:100,000 scale data from USGS DLG

Data from different sources and scales can vary widely



intro_gis.ppt 29

Scale Issues

• 1:1,000,000 scale data from DCW (DMA)




intro_gis.ppt 30

Scale Issues

•1:2,000,000 scale data from USGS DLG




intro_gis.ppt 31

Scale Issues

• one inch on the map equals 200 inches on the ground?

or

• one inch on the map equals 200 feet on the ground?_

• “one to two-hundred”: does this mean

Beware of scale statements



intro_gis.ppt 32

Course Sample Data

• Original data sources

• Legacy maps

• USGS digital line graphs

• DNR data

• GPS surveys

• Digital orthophoto interpretation_

Pack Forest GIS database



intro_gis.ppt 33

Course Sample Data

• CD directory pfdata• Forest stands• Streams• Roads, trails• Soils• Elevation contours• Culverts• Forest inventory data• Digital orthophotos• Digital elevation model• …

_

Pack Forest GIS database



intro_gis.ppt 34

Course Sample Data

• CD directory esridata• Worldwide data sets

• countries• major rivers

• United States data• states• counties• cities• rivers• roads

• Canada• Mexico

_

ESRI Sample Data



intro_gis.ppt 35

Sample Data

Unless otherwise specified,

Projection STATEPLANEWashington South Zone (State Plane 5626 or FIPSZone 4602)

Datum HPGN (a.k.a. NAD83/91)Units FEET Spheroid GRS1980_

Pack Forest GIS database projection & coordinate definition

CFR 250/590 Introduction to GIS © Phil Hurvitz, 1999-2000intro_gis.ppt 1 Introduction to GIS Spatial (coordinate) data model Relational (tabular) data.

Documents

vector data model cad

vector data model polygons

vector data model lines

spatial data model gis

format data model

sloppy data

vector data model points

arcview coordinate data