Topographical or relief data in Map APIs

I was wondering if anyone knew of any map APIs that offer topographical or relief data? I've had a quick look at Google and Bing APIs, but could find nothing there.

Google allow you to view a map as TERRAIN, which means you can see the topography of a map, but I want to be able to get at that data - i.e. if I were to draw a line between 2 points on Google Maps, I want to know how high above see level points along that line are.

Is this possible with any map A开发者_如何学GoPIs out there?

Thanks for your time!

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Here's a simple example of height along a route.

I use USGS to obtain the elevation data, Google Maps API to plot the route and Google Charts to draw the elevation profile.

Full details in the associated tutorial.

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Here are a few web services that provide elevation data:

• USGS Elevation Query Web Service
• EarthTools
• GeoNames

Also, this site can search each of them