How to look up elevation data by lat/lng

ruby google-maps gis geospatial
Bryan picture Bryan · Jul 7, 2009 · Viewed 11.3k times · Source

I am planning an app that will need the ability to look up the elevation of geographic points by lat/lng. Ideally I would like something that would work worldwide, but US-only would also suffice. I have looked at using the USGS Elevation Query Web Service, however it only allows you to query for one point at a time, and I will need to look up several hundred, and possibly up to several thousand. I also considered downloading & hosting the National Elevation Dataset myself, but it's almost 100 gigs, and apparently the USGS only allows you to download 1.5 gigs at a time.

Can anyone familiar with GIS recommend a good solution for me? I'm looking for something as lightweight & simple as possible. I am completely new to GIS, so I would really appreciate suggestions on where to get the data, how to store it, and how/what to use when working with it.

Thanks in advance.

EDIT: Just to clarify, the data points I need are not predetermined. They are arbitrary points chosen by the user (by interacting with a google maps mashup), so I do need to be able to query for any point, not just a small subset.

EDIT 2: If there is no lightweight or simple solution, I'll take whatever I can get =)

Answer

rburhum picture rburhum · Jul 10, 2009

I'll give you one of the best "secrets" that I learned throughout the years after going through many different pains (leeching scripts, manual clicking, etc). It is an old-school trick... contact a real person there!

The best way do get the NED elevation dataset is to contact USGS's Eros group directly at bulkdatainfo_at_usgs.gov

You send them an external drive and after 4 to 8 weeks (usually much less than that) they will send you the entire dataset that you requested.

Then use GDAL to query your points in a way similar to this example. You may want to read the Affine Geotransform section of the GDAL Data Model

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