[gdal-dev] DTED Elevations with Java and gdal

[Frank Warmerdam]

On Wed, Oct 19, 2011 at 1:23 PM, Roger Viton <wsureshoot at fastmail.fm> wrote:
> There have been other threads on this topic.  The threads seem to die with no
> clear solution presented.
>
> Does anyone have a Java example on how to get elevations from a DTED file?
>
>
> org.gdal.gdal.Dataset dataset = org.gdal.gdal.gdal.Open(<some dted file>,
> org.gdal.gdalconst.gdalconst.GA_ReadOnly);
>
>
> With an x y point how can the elevation be derived?
>
>
> We have been able to run GDALtest.java against a DTED file with no problem.
> There does not seem to be any reference to any elevation in DTEDtest.java
>
> Just want to get the elevation at a point.

Roger,

There is nothing special about a DTED file compared to other
raster files.  The only thing to keep in mind is to load the
elevation into a buffer with a better type than Byte.  The
gdal/swig/java/apps/GDALTestIO.java shows an example of
reading into a Float32 buffer.

You have not been specific about the coordinate system of your
x y point so it is hard to be specific.  As Kyle suggests the
gdallocationinfo program does what you want, but in C++ with
some variations.  It should be instructive even if you don't want
to do it in C++.

Assuming your x and y are in longitude and latitude, then you
should just need to use the geotransform from the file to
transform the x/y into pixel/line coordinates suitable for use
with the RasterIO() method.  If you only want one pixel then
just read into a 1x1 buffer.

Best regards,
-- 
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