Friday, November 09, 2007

Filters for Canadian Geospatial Data Infrastructure

We had a great time with the CGDI Interoperability Project in Canada this week. I'll try to describe some of the events over the next few days. One of the highlights (for me at least) was our new Filter Builder tools based on OGC Filters and CGDI.

One part of the demo showed how emergency analysts could use OGC Filters, WFS services and data from CGDI - for analysis. The demo used a simulated release plume polygon to construct new features such as impacted roads and places. This involved intersecting release plume polygons with impacted areas, but used the CGDI service to do the analysis.

Here's how it worked - we used CarbonArc PRO to select an existing GML feature (a release plume polygon), construct a Filter Encoding request using Spatial Operators (in this case it was the Spatial Operator "Intersect"), and then send it to CubeWerx and acquire impacted roads and places. All done in real time - very cool.

The tools are based on Filters - the basic idea of an OGC Filter is to provide a SQL-like spatial and logical language to make advanced data queries possible in a distributed environment. Filters do this using a series of logical ("AND" this, "OR" that), comparison (is this "Equal To") and spatial (does that road "Intersect"?) operators.

The Filter Encoding (FE) specification, when wrapped up into easy-to-use tools, lets SDI users quickly add complex and powerful queries to their work flows.

All this means a big change from the days when analysis was done using GIS on the desktop.


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