Elevation update question. by lignumaqua - 2013-08-12

I think I misspoke slightly (I've slept since we put this in place! ). It was actually some of the ASTER data that was particularly bad for the Netherlands (although annoyingly it was very good in other areas of the world and has good coverage). Now the number of queries is so much reduced from the intitial rush when we were trying to get 3 million datapoints that, to avoid problems, we don't use that data at all anymore. SRTM is much better when it's available.

For the US there is a USGS database GSAK uses, and that data is generally accurate so we haven't seen the problem over here.

The complete system uses four databases (used to be five with ASTER) USGS, two different SRTM databases, and Google as a last resort.

This is the data GSAK has right now (at the time of writing) on 3,680,671 points. It's interesting to see how it follows the roads in the large mostly unpopulated/uncached areas of Australia and the central area of the USA.