[Gdal-dev] Using DEM

[Frank Warmerdam]

Sylvain Rioux wrote:
> Hi,
>  
> In GDAL using a USGS DEM file,  is it possible to find the elevation of 
> a point from its coordinates (lat-lon or projected)? Does GDAL have some 
> kind of interpolation method to allow this?

Sylvain,

The short answer is no.  You can use PROJ.4 or OGRCoordinateTransformation
services to reproject a location into the coordinate system of the USGS DEM
file and then convert to pixel/line coordinates.  Then read the four pixels
in the neighbourhood of that pixel/line location and perform bilinear
interpolation.

I have done this in the general warper resampler code, but I am not sure it
would work well to running to warper to produce a single output pixel image.

Best regards,
-- 
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