[GIS] Read dted with gdal in c++

dtedgdal

I need to find the elevation of lat and long point using a dted map. I read that gdal can read this kind of map. I didn't find a tutorial. I read about gdal here but it's not very "user-friendly". Can you give me any code snippet (only an hint) to read a single value of a dted map?

Best Answer

I have written GDAL programs using C++ and C#. It is incredibly easy to use.

I advise you to download the source code. You'll find the source for gdallocationinfo, which is their command-line tool that does exactly what you want. You can use it as the lever to get going.

If using gdallocationinfo on the command line won't work for you.

-reilly.

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To find which feature the coordinate is near, you first need to build an R-Tree index of bounding boxes or envelope of each feature. A popular library for this is libspatialindex.

Secondly, you would then need to know for each of the matched features from your R-tree, which ones match. GDAL/OGR does have some operations based on GEOS to see if the geometry "contains" the point of interest, and you can extract the field info. See the OGRGeometry Class Reference for Contains, Touches, Within, etc. that can perform the geometry relation operator.

Personally I wouldn't do any of the above, because it would take me too long to figure out the coding, and I know there are faster ways. (I would loading all shapefiles in a PostGIS database, then query the locations using SQL.) However, it is understandable if this GIS functionality needs to be embedded in an existing project without adding more complicated dependencies, such as a database server.

QGIS GDAL – Batch Processing DEM Rasters

Looking at the dialog here, you might have some odd POSIX user permission stuff getting in the way. Or possibly DOS line endings (rather than UNIX). Rather than making a file, just do the loop from the command prompt, by typing it out in the terminal. I do this routinely, without the need of making a shell script file.

Typing this the first time, you should see the prompt character in the first column change from $ to > (don't type these!) until the end of the loop block:

$ for f in *.asc
> do
> echo "Processing $f"
> gdaldem hillshade  -z 2.0 -az 345.0 -alt 50.0 $f $f-HS.tif
> done

(Note: this is identical to yours, except I replace %f with $f.) After this, you can type the up key to see the previous command.

for f in *.asc; do echo "Processing $f"; gdaldem hillshade  -z 2.0 -az 345.0 -alt 50.0 $f $f-HS.tif; done

It is shown as a one-line condensed version with semi-colons, which you can use and modify (if needed) for further work from the command prompt.

Best Answer

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