GeoNamesElevationExtractor

From fmepedia

The transformer returns an elevation of a feature specified by latitude and longitude.

The transformer uses GeoNames web service (www.geonames.org). The service is free and works under cc-by licence.

Elevations are extracted with one of the following services: GTOPO30 (http://www.geonames.org/export/web-services.html#gtopo30) (default) is a global digital elevation model (DEM) with a horizontal grid spacing of 30 arc seconds (approximately 1 kilometer). For oceans it returns nodata assigned to -9999.

SRTM3 (http://www.geonames.org/export/web-services.html#srtm3) data derived with the radar system that flew onboard the Space Shuttle Endeavour during an 11-day mission in February of 2000. It has better resolution (data points located every 3-arc-second - approximately 90 meters) but lesser coverage (only land areas between 60 degrees north and 56 degrees south). For ocean it uses nodata value set to -32768.

The output features get two attributes - _elevation (in meters), and _http_status_code, which reports whether the request to the service was a success (code 200) or a failure (codes may vary).

The attached workspace takes the capitals of the world in FFS format, extracts latitude and longitude for each feature, sends requests to the service, gets back elevations, and builds a diagram showing graphically the elevations from highest capital (La Paz, Bolivia) to the lowest (there is quite a few capitals where the elevation is either 0, or has nodata value).