I'm spinning my wheels trying to find an existing, free source for TMS or WMS elevation data that doesn't involve a long-winded clickabout or an emailed url. This question has a similar purpose, but the answers offered aren't compatible with what I want to accomplish.
My goal isn't to show tiles in a map, rather I want to automatically calculate some details about a user-selected drainage corridor (stretches people want to canoe/float, to be specific). For example, once the user sets an area (+/- 10 miles ^2) and choses their endpoints, I'd like to derive information like drop in elevation between endpoints, overall slope of the run, and graph of the longitudinal profile for the reach would be a nice start. ..my thinking is, maybe I can implement difficulty metrics.
Ideal data traits:
- 30-meter pixels,
- png or tiff, tiles to mosaic or a custom BBox area is fine
- source offers full coverage of the US (at least the 48 contiguous)
- actual elevation values (i.e. I'm not looking for hillshades or textures.)
Example bounding area:
bbox=-93.424564,36.993675,-93.331009,37.056170
Alternatively, any approach conducive to auto-download of DEM tiles or clips based on a fixed grid or path/row combination would work, so long as there is either a preexisting grid to work with, or enough theory to pre-generate a grid. Of course, key to this is access to a repository of data that allows direct url or ftp access.
I'm very curious to see what people think.
http://geobrain.laits.gmu.edu/wcs4dem.htm It seems the makers of DEM Explorer (above) provide a WCS gateway that serves geotiff DEM clips for BBox regions. Thanks to @BradHards for finding this. Here's an example call to the WCS service against the example bounding region I noted above:
http://geobrain.laits.gmu.edu/cgi-bin/gbwcs-dem?service=wcs&version=1.0.0&request=getcoverage&coverage=SRTM_30m_USA&bbox=-93.424564,36.993675,-93.331009,37.056170&crs=epsg:4326&format=image/geotiff&store=true
Best Answer
The current approach for gridded/point data is Web Coverage Service or WCS. This is well supported in a range of commercial and open source servers (e.g. GeoServer), and also has pretty good support at the client level (e.g. owslib)
As you've shown in your updated question, access to WCS is a lot like WMS or other OGC services.
There probably isn't as many WCS services as there are WMS, WFS or TMS services. WCS seems to be mostly oriented to use in scientific analysis (e.g. vegetation, weather and other atmospheric phenomena, some population info), rather than direct use. I did find one elevation data provider with a nice description of how to use it at GMU's Geobrain page. That provider was called wcs4dem, and is at http://geobrain.laits.gmu.edu/wcs4dem.htm
If your future needs extend to more than a public service is reasonably capable of, you could transition to your own WCS server (after downloading DEM data from some source that meets your needs) without significant changes to your code.