GIS Lecture 5 Importing Spatial and Attribute Data

1. GIS Lecture 5 Importing Spatial and Attribute Data

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

3. GIS Data Sets

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

5. ArcInfo

6. 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

7. Coverage Attribute Table Polygon Coverage

8. Coverage Attribute Table Point Coverage

9. Coverage Attribute Table Line Coverages

10. B E 1 2 Pine St. 733 A 734 F C Oak St. 3 4 D G ArcInfo Coverages • Advantages • Many feature types • Polygons share borders • Area/Perimeter Fields • Disadvantages • Cannot edit in ArcMap

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

12. 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

13. 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

14. ArcView Shapefiles

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

16. CAD Layers

17. Aerial Photos • Combining Grid and Vector Maps

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

19. 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

20. Event Files X,Y Coordinates

21. Event Files

22. Map Projections

23. 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

24. Distortion Examples

25. Mercator Projection: Distortion

26. Robinson Projection: Distortion

27. 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

28. 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.

29. Coordinate Systems

30. Coordinate Systems • Spherical/Polar • Geographic Coordinate System • Rectangular • State Plane • UTM

31. Geographic Coordinate System • Latitude and Longitude • Census Bureau TIGER files • Geographic • Coordinate • System Grid

32. Longitude: Meridians

33. Latitude: Parallels

34. Origin • Longitude (prime meridian) 0 • Latitude (equator) 0

35. Coordinates Pittsburgh 40 -80

36. 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°

37. 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

38. Rectangular Coordinate Systems State Plane Coordinates • Local Governments UTM • US Military • Rectangular • Coordinate • System Grid

39. 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

40. 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

41. State Plane Coordinate Zones

42. State Plane Coordinate Zones

43. City of Pittsburgh as Geographic Coordinates

44. City of Pittsburgh as State Plane Coordinates

45. Universal Transverse Mercator System (UTM) • 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

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

47. Data Sources

48. 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

49. US Census • www.census.gov • TIGER Maps • Summary File(SF) Tables

50. 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