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I'm looking for GIS program that has good support for KML/KMZ or GPX route files and also has free hand selection tool. Right now I use 3dem and it would be perfect for my needs if only it had that free hand selection tool. All I need is to load a terrain (HGT file), and then select only the part of it that is close to my route plan (KML file). And finally save that selected part to DEM file or any other format that I could edit later in some 3D modeler.

Can you point me to some GIS program that fully meets my requirements?

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You should be able to do this task in a variety of GIS applications. Here's a step-by-step for QGIS.

  • Download QGIS from: http://www.qgis.org/
  • Import the KML or GPX polyline (Layer > Add vector layer...).
  • Import the elevation data (Layer > Add raster layer...)
  • Either: create a buffer area around the polyline (Vector > Geoprocessing tools > Buffer(s))
  • Or: manually define the area to clip by creating a new polygon shapefile (Layer > New > New Shapefile Layer...)
  • Clip the elevation data to the buffered area (Raster > Extraction > Clipper)

If your track spans multiple HGT tiles you'll need to mosaic them. You can do this with a virtual raster catalog (Raster > Miscellaneous > Build Virtual Raster (Catalog).

Note that if you buffer the polyline without reprojecting the SRTM elevation data (which comes in WGS84) the units of distance will be in decimal degrees, not meters. You can reproject the data by going to Raster > Projections > Warp (Reproject).

example

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