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GIS Lecture 5 Importing Spatial and Attribute Data

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Outline•GIS Data Sets•Map Projections•Coordinate Systems•GIS Data Sources

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GIS Data Sets

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GIS Data Sets• ArcInfo Coverages• ArcView Shapefiles• CAD Files• Aerial Photos• Event Files

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ArcInfo

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ArcInfo Coverages

AAT Arc Attribute TableARC Arc coordinates and topologyBND Coverage minimum and maximum coordinatesCNT Polygon centroid tablePAL Polygon topologyPAT Polygon/Point Attribute TableTIC Tic coordinates and IdsDBF Database Table

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Coverage Attribute TablePolygon Coverage

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Coverage Attribute TablePoint Coverage

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Coverage Attribute TableLine Coverages

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ArcInfo Coverages•Advantages-Many feature types-Polygons share borders-Area/Perimeter Fields

•Disadvantages-Cannot edit in ArcMap

B

A

D

1 2

3 4

Pine St.

Oak St.734C

E

G

F733

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ArcInfo Export files•.e00 export exchange file•ArcCatalog translates into ArcGIS•Creates coverages

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ArcView Shape Files Advantages•heads-up digitizing and editing•less storage/rapid display •can export to CAD

Disadvantages•one feature type•no area or perimeter with new shapefiles

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ArcView Shape Files From 3 to 5 Files•.shp - stores feature geometry•.shx - stores index of features•.dbf - stores attribute data•.sbn and .sbx - store additional indices

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ArcView Shapefiles

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CAD Files Why CAD Drawings?• Better Precision for Digitizing -AutoCAD / Microstation-.DWG / .DXF

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CAD Layers

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Aerial Photos Combining Grid and Vector Maps

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Orthophotography Digital imagery in which distortion from the camera angle and topography have been removed, thus equalizing the distances represented on the image

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GPS•Global Positioning Systems•Earth-orbiting satellites broadcast precisely timed radio signals•GPS receivers determine positions on the ground by calculating distances from three or more satellite transmitters•More expensive than traditional optical and electronic methods

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Event FilesX,Y Coordinates

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Event Files

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Map Projections

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Map Projections and Distortion Map projections produce distortion in one or more spatial properties:•Shape, area, distance, and direction•Specific projections eliminate or minimize distortion

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Distortion Examples

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Mercator Projection: Distortion

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Robinson Projection: Distortion

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Projection Important•Measurements used to make important decisions•Comparing shapes, areas, distances, or directions of map features •Feature and image themes are aligned

Los Angeles

New York

Los Angeles

New York

Projection: MercatorDistance: 3,124.67 miles

Projection: Albers Equal AreaDistance: 2,455.03 miles

Actual distance: 2,451 miles

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Projection not Important Business applications•Not of critical importance. •Concerned with the relative location of different features

On large scale maps - street maps•Distortion may be negligible •Map covers only a small part of the Earth's surface.

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Coordinate Systems

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Coordinate Systems•Spherical/Polar-Geographic Coordinate System

• Rectangular-State Plane-UTM

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Geographic Coordinate System• Latitude and Longitude• Census Bureau TIGER files

Geographic Coordinate System Grid

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Longitude: Meridians

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Latitude: Parallels

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Origin° Longitude (prime meridian)0

° Latitude (equator)

0

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CoordinatesPittsburgh

-80

40

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Degrees, Minutes, and Seconds (DMS): 40°26’2”N latitude -80°0’58”W longitude

Decimal Degrees (DD) 1 degree = 60 minutes, 1 minute = 60 seconds 40°26’2” = 40 + 26/60 + 2/3600 = 40 + .43333 + .00055 = 40.434°

Pittsburgh’s Point

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World circumference through the poles is 24,859.82 miles, so for latitude: 1° = 24,859.82/360 = 69.1 miles 1’ = 24,859.82/(360*60) = 1.15 miles 1” = 24,859.82*5,280/(360*3600) = 101 feet

Length of the equator is 24,901.55 miles

Translated to Distance

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Rectangular Coordinate Systems

State Plane Coordinates- Local Governments

UTM- US Military

Rectangular Coordinate System Grid

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Rectangular Coordinates

200

400

0 200 4000

(100, 200)

(400, 300)

East (Feet)

Nor

th (F

eet)

Has all positive Cartesian coordinates in feet, called false eastings and false northings

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State Plane Coordinate System•Established by the U.S. Coast and Geodetic Survey (now the National Ocean Survey)•At least one for each state•Rectangular (x,y) coordinates•125 zones, following state and county boundaries each with its own projection:

Lambert conformal projection for zones with east-west extent

Transverse Mercator projection for zones with north-south extent

•Cannot have zones joined to make larger regions

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State Plane Coordinate Zones

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State Plane Coordinate Zones

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City of Pittsburgh as Geographic Coordinates

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City of Pittsburgh as State Plane Coordinates

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•NIMA - Military grid system

•Based on the transverse Mercator projection

•Applied to maps of the Earth's surface extending from the Equator to 84 Degrees north and 80 degrees south latitudes

Universal Transverse Mercator System (UTM)

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UTM Zones in the Contiguous United StatesWorld is divided into 60 north-south zones, each covering a strip 6° wide in longitude

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Data Sources

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Other Sources of GIS Data

•US Census•ESRI Web Sites and Media Kit•Local Agencies•Land Surveys •Satellite Remote Sensing•Existing Paper Maps•Other WEB Sites

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US Census• www.census.gov- TIGER Maps- Summary File

(SF) Tables

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Census Tracts (TIGER) Small, relatively permanent statistical subdivisions of counties

•delineated by local committees in accordance with Census Bureau guidelines •between 1,000 and 8,000 people (in general)•1,700 housing units or 4,000 people•homogeneous population characteristics (economic status and living conditions)• normally follow visible features•may follow governmental unit boundaries and other non visible features• more than 60,000 census tracts in Census 2000

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State Census Tracts

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County Census Tracts

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City Census Tracts

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Census Blocks Groups Block groups (BGs) are the next level below census tracts in the geo-graphic hierarchy - a subdivision of a census tract -400 housing units, with a minimum of 250, and a maximum of 550 housing units -follow clearly visible features, such as roads, rivers, and railroads.

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Census Block Groups

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Census Blocks Smallest geographic area for which the Census Bureau collects and tabulates decennial census information.

Block boundaries are visible (street, road, stream, shoreline, etc.) or nonvisible (county line, city limit, property line, etc.) features.

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Census Blocks

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Other Census TIGER Layers

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Summary File (SF) Tables American Factfinder

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SF1 Tables

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SF2 Tables

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SF3 Tables

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ESRI’s Website

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ESRI Media Kit•Data and Maps•8 CDs and DVDs-Data & Maps and StreetMap USA (DVD)-Image Data (DVD)-Global Imagery (DVD)-World, Europe, Canada, and Mexico (CD)-United States (CD)

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Local GIS Departments

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Land Surveys•Specifies boundaries, rights-of-way, and other legal descriptions•Surveyors use optical and electronic instruments to measure precise control point locations established by geodesists•High quality data, but takes a lot of time

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Existing Paper Maps•Vector Digitizing•Raster Scanning

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Other GIS WEB Sites•http://www.gisportal.com/

•http://www.pasda.psu.edu/

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Linking to Internet Sites PASDA Example

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Linking to Internet Sites Geography Network Example

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Summary•GIS Data Sets•Map Projections•Coordinate Systems•GIS Data Sources