Case Study: Providing a query API to vector GIS data.

Assumption: We have a variety of shapefiles, or other such GIS layers. We want people to be able to

• Provide a location (or address), and get back those attributes of the features that intersect the location
• Provide a spatial query (eg bounding box) and get back all features and associated geographic boundaries that intersect the bounding box
• Provide any feature attribute, and get back the entire feature, including the full geographic coordinates

Recommended Software:

• FeatureServer? (for the data interchange)
• A Geocoder (geopy) to turn addresses into locations

Plan:

• to do *

Results:

Query all attributes by address:

• Currently only returns XML/GeoRSS - this should be integrated into a difference interface soon. But for now it does let you parse out any attributes you may want by address.
• Base Service URL:
  • http://services.eactive.org/voteinfo
• Example Queries
  • by Address query
  • by Lat/Lon query

Query for full feature by attribute or spatial extent:

• Optional Parameters:
  • format - output format
    • JSON (default), GeoJSON, KML, Atom, GML, WFS
  • Optional Query/Filter Parameters
    • see http://svn.featureserver.org/trunk/featureserver/doc/Querying.txt
• Base Service URL
  • http://services.eactive.org/features/
• Example Queries:
  • A neighborhood feature in JSON if you know the name of it: query
  • KML format of US Congressional Districts (108th congress) in Washington held by Democrats query
  • A maximum of 10 block groups within a smallish area (eg a google map view) in GeoRSS/Atom format: query
• Homework:
  • Modify any of these queries so the format is KML - then paste it into the search window of http://maps.google.com