Announcement: The GIS in the Cloud (App Engine + JTS) reference project is now available at http://giscloud.appspot.com with the source code available at http://giscloud.googlecode.com (documentation forthcoming).
While many GIS/spatial App Engine discussions center on the python SDK (with pre-computing grids or geocells and heavy lifting done with set membership in the datastore), this reference project uses the Java Topology Suite (http://www.vividsolutions.com/jts/jtshome.htm) within the App Engine server to demonstrate point-in-polygon and polygon-in- polygon spatial queries. The GIS in the Cloud app is pure Java and was built with * Google App Engine SDK for Java * Google Plugin for Eclipse * Google Web Toolkit * Google Web Toolkit API Libraries - Google Maps 1.0 Library * Java Topology Suite The Java Topology Suite was ported to C++ and became GEOS, which was embedded in PostgreSQL to become PostGIS, allowing users access to spatial functions within SQL. While App Engine does not give us spatial functions in GQL, the GIS in the Cloud app will demonstrate a GQL/JTS combination to accomplish the same effect. The current version of the application does demonstrate use of the datastore (TODO), but it does employ JTS to query point-in-polygon and polygon-in-polygon. Single clicks on the map trigger the point-in- polygon test (the point is the map center and the polygon is Salt Lake County). With zoom or drag, the polygon-in-polygon test is triggered. The first polygon is the map bounds and the second is Salt Lake County. Future versions will use the datastore and be able to access OGC Well Known Text (WKT) from which geometry can be created for features such as: tracts, census block groups, census blocks, and parcels. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en -~----------~----~----~----~------~----~------~--~---
