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GIS Lecture 5 Importing Spatial and Attribute Data. Outline. GIS Data Sets Map Projections Coordinate Systems GIS Data Sources. GIS Data Sets. GIS Data Sets. ArcInfo Coverages ArcView Shapefiles CAD Files Aerial Photos Event Files. ArcInfo. AAT Arc Attribute Table
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GIS Lecture 5 Importing Spatial and Attribute Data
Outline • GIS Data Sets • Map Projections • Coordinate Systems • GIS Data Sources
GIS Data Sets • ArcInfo Coverages • ArcView Shapefiles • CAD Files • Aerial Photos • Event Files
AAT Arc Attribute Table ARC Arc coordinates and topology BND Coverage minimum and maximum coordinates CNT Polygon centroid table PAL Polygon topology PAT Polygon/Point Attribute Table TIC Tic coordinates and Ids DBF Database Table ArcInfo Coverages
Polygon Coverages • Area and perimeter automatically calculated
B E 1 2 Pine St. 733 A 734 F C Oak St. 3 4 D G Polygon Coverages Polygons share borders
Line Coverages • Length automatically calculated
ArcInfo Coverages • Advantages • Many feature types • Shared borders • Automatic Area/Perimeter/Length fields • Disadvantages • Cannot edit in ArcMap
ArcInfo Export files • .e00 export exchange file • ArcCatalog translates into ArcGIS • Creates coverages
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
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
CAD Files • Why CAD Drawings? • Better Precision for Digitizing • .DWG / .DXF
Aerial Images • Combining Grid and Vector Maps
Event Files X,Y Coordinates
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
Projection Important • Measurements used to make important decisions • Comparing shapes, areas, distances, or directions of map features • Feature and image themes are aligned New York New York Los Angeles Los Angeles Projection: MercatorDistance: 3,124.67 miles Projection: Albers Equal AreaDistance: 2,455.03 miles Actual distance: 2,451 miles
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.
Coordinate Systems • Spherical/Polar • Geographic Coordinate System • Rectangular • State Plane • UTM
Geographic Coordinate System • Latitude and Longitude • Census Bureau TIGER files • Geographic • Coordinate • System Grid
Origin • Longitude (prime meridian) 0 • Latitude (equator) 0
Coordinates Pittsburgh 40 -80
Pittsburgh’s Point • 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°
Translated to Distance • 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
Rectangular Coordinate Systems State Plane Coordinates • Local Governments UTM • US Military
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 Mercatorprojection for zones with north-south extent • Cannot have zones joined to make larger regions
400 (400, 300) North (Feet) 200 (100, 200) 0 0 200 400 East (Feet) Rectangular Coordinates • Has all positive Cartesian coordinates in feet, called false eastings and false northings
State Plane Coordinate Names • North American Datum of 1927 (NAD27) • American Datum of 1983 (NAD83) • "High Accuracy Reference Network" (HARN) • "High Precision GPS Network" (HPGN)
Universal Transverse Mercator System (UTM) • Developed by the NATO in 1947 • Military grid system • Based on transverse Mercator projection • Applied to maps of the Earth's surface extending from the Equator to 84 Degrees north and 80 degrees south latitudes
UTM Zones World is divided into 60 north-south zones, each covering a strip 6° wide in longitude