Map Data and Development

Map Data and Development

Without data, you don't have a GIS

data that already exists; find it or buy it
geocode existing paper maps
develop data from scratch

Existing Sources

National & Federal:

NationalAtlas.com - excellent resource for large area (small scale) data
USGS (DLG, DOQ, DRG, DEM) - www.usgs.gov
NOAA - weather, marine and aeronautics - www.noaa.gov

US Bureau of Census - TIGER (topologically integrated geographic encoding and referencing) data broken into blocks, tracts, and districts (FIPS codes link)

www.census.gov (also found at ESRI website - 2000 census data)

National Resource Conservation Service (NRCS) - Hyrological Units - www.ftw.nrcs.usda.gov/huc_data.html

State Resources:

Fire and Resource Assessment Program (CDF) frap.cdf.ca.gov
Department of Conservation - Farmlands - www.consrv.ca.gov/dlrp/index.htm
Department of Fish & Game - Wetlands - maphost.dfg.ca.gov/wetlands/
- Wildlife & Habitat Data - www.dfg.ca.gov/whdab/html/programs.html
Department of Transportation (CalTrans) - www.dot.ca.gov/hq/tsip/TSIPGSC/library/libdatalist.htm
Check CERES for hub of all data ceres.ca.gov

Regional & Local data:

Placer County Data on disk; call local cities and counties

Tahoe Basin - tahoe.usgs.gov/

Sacramento River Conservation Area - www.sacramentoriver.ca.gov/

Parcel level data for South Bay Area (ask instructor)

Miscellaneous:

ESRI's Data Site - www.esri.com/data/online/index.html

Calif. Spatial Info. Library (CaSIL) - www.gis.ca.gov

California Legacy Project - http://www.legacy.ca.gov/

ESRI Data & Maps 2000 - http://www.lib.vt.edu/subjects/maps/esridata2000.html

Many GIS Links - http://www.pacificsites.com/~cbrooks/gis1.shtml

GeoCommunity - http://data.geocomm.com/catalog/US/61069/sublist.html

Projection Information - http://home.comcast.net/~rickking04/gis/spc.htm

Digitizing - traditional way to retrace the map lines of the original map with puck

paper maps converted to digital format (geocoding)
- (60 to 90 percent of time)
large drafting like table with electronic sensors
many times maps are transferred to mylar and traced on light table
- tedious, prone to errors and time-consuming
Automated digitizing or scanning (drum scanner)
- must be set to recognize certain geographic features
  - usually simple mylar map with few features

Developing Data from Scratch

Field collection - GPS unit (Pacchetti) build attribute tables on the fly
Imagery and Remote Sensing - use of orthorectified imagery to achieve map accuracy
- large scale imagery flown with airplanes (Cupertino)
- satellite imagery - less accurate and less expensive
- multispectral - land cover, vegetation change, soil types, crop stress, etc.
heads-up digitizing - to create parcels or often to match aerial photographs after digitized
- software packages such as AutoCAD or ArcInfo
- control points to georeference "linework"
  - paper units to a real-world coordinate system

Scale and precision

Integrating other data may be inappropriate given the level of detail

USGS or TIGER roads may not line up with GPS biological survey (TIGER Metadata notes)

E.g. found certain species on west side of road and surveyed exact location; then USGS roads show features on East side (50 m accuracy)
Aerials (DOQ) show trails off, but aerial might be off!
- important to be "orthorectified" photos
- Use control point to verify accuracy

ArcView File Types

Shape Files (convert to shape file command)
ArcInfo Coverage (several folder including .prj file)
- eOO "export" files
  - how to import into ArcView 3.2
AutoCAD (.dwg and .dxf)
Tiff, JPEG, Mr.SID (all compressed files - must have extension on)
Other vendors - GeoMedia and Map Info
othe database files - Dbase (.dbf), Oracle, Access, etc.

Index