Cool service, albeit it's for smaller uses. The limit is 25,000 requests a day. This sounds like alot, until you realize each point is a request. So, you want elevations for a 100 mile route drawn on a map? That's about 2-3000 points, so you only get 10-20 of such routes before hitting your daily limit.<p>Other issue is the accuracy: I am not sure the base DEM resolution they are using, but my guess is it's the standard 10meter spacing between points inside US and territories, and 30meters outside. 10meter grid spacing isn't bad at all, it's actually pretty good, but their algorithm for interpolating is non-existent. For any point not directly on a grid point, they just average the four surrounding elevations and return that. I have played with several interpolation schemes, and I have found either a bilinear or a cubic interpolation for interior points to be vastly superior to a nearest neighbor or averaging scheme. Differences can be easily up to 10 meters for a 10meter grid spacing.<p>I had been hoping they'd release this, but I'll stick to my home-brewed service with the 500gig NED at 10 meter resolution (1/3 arcsecond). No API limits :)
The NASA Shuttle Radar Topographic Mission (SRTM) has provided digital elevation data (DEMs) for over 80% of the globe. This data is currently distributed free of charge by USGS and is available for download from the National Map Seamless Data Distribution System, or the USGS ftp site. The SRTM data is available as 3 arc second (approx. 90m resolution) DEMs.<p><a href="http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp" rel="nofollow">http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp</a>
Wonder if this would be accurate enough for a GPS -> bike route translator. Like say you want to see the altitude throughout your bike right from the gps you recorded.