Sources of GIS data

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Sources of GIS data

• J426 Class 15
• March 3, 2009

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Overview

• Paper maps
• Aerial photos
• Satellite imagery
• Organization records
• Global positioning system collection

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Paper maps

• Most common form for recorded geographic
  information
• USGS topographic maps
• Specialized maps portraying specific data
• Flood hazards
• Soils
• Wetlands
• Maps created by local and state agencies

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Paper mapdowntown indianapolis
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Aerial photos

• Relatively inexpensive source of geographic
  information
• Can provide information for detailed, large-scale
  mapping, as detailed as manhole covers
• Can achieve accuracy of one foot or less
• Can be interpreted to provide information on
  other topics such as land cover
• Digital orthophotos, rectified images can be used
  directly in GIS

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Digital orthophotodowntown Indianapolis
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Satellite imagery

• Information generally obtained for raster-type
  grid cells
• Information available at various wavelengths
• Classification procedures can be used to
  interpret land use, land cover
• Commercially available
• Pixel size available down to 0.6 meters, which
  can provide quite detailed images

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Land cover for Indianapolis from LandSAT
satellite imagery
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Satellite image of IUPUI from Google Maps
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Organization records

• It has been estimated that at least 80 percent of
  the records kept by public agencies have
  geographic locations
• Such locational identifiers allow such records to
  be used in geographic information systems

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Geographic identifiers

• Addresses
• Intersections
• ZIP codes (including ZIP4)
• Milepost markers on highways

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Criminal justice records

• Calls for service
• Officer incident reports
• Basis for IPD Tiburon system
• Court records
• Corrections records
• Addresses of persons on probation and parole

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Police incident records from IPD Tiburon system
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Global Positioning System collection

• System of satellites from which location can be
  determined
• GPS receivers can record latitude and longitude
  (or position in other coordinate systems)
• Coordinates can be downloaded and directly
  entered as point features into GIS

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Global Positioning System receivers
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Law enforcement applications of GPS

• GPS receivers are being used by some state police
  agencies to record locations of accidents and
  other incidents
• Greatest utility in jurisdictions in which
  addresses may not be available as geographic
  identifiers

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GPS and Mobile Citation software

• Captures location
• After entry of drivers license number, queries
  DMV database and fills in info
• Prints out ticket
• Transmits citation information

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GPS accuracy

• Accuracy depends on quality of receiver and use
  of auxiliary methods (differential GPS) to
  enhance accuracy
• Can achieve accuracy to less than 10 cm
• With high levels of accuracy, could be used to
  map locations within accident or crime scenes