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I have a set of Digital Terrain Model ASCII grid files; they're the output of a LIDAR survey over our city, and so cover adjacent areas. Now I need to "cut" a polygon out of these files; this polygon is in GeoJSON format and can overlap across more than one of these DTM files.

Then the cut area should be put into a new ASCII grid file, because it needs to be passed to an existing program our team created, with the area outside the polygon.

Here is a diagram to give a more visual description.

Magic needed!

How can I execute this operation?

I have GDAL installed, and I have admin rights, so I can install any software I need. Of course it would be better if it was Open Source, but the most important things is that I will have to automate this operation next, so something that works from the command line or has a Python API would be ideal for me.

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Without testing this might work.

1) Create a virtual mosaic from all your source files

gdalbuildvrt mosaic.vrt *.asc

2) Use gdalwarp and crop the mosaic to cutline

gdalwarp -of [your format] -cutline your_geojson.json -crop_to_cutline mosaic.vrt cropped_output.[ext].

You may need to give also the layer name for the GeoJSON cutline which is always "OGRGeoJSON".

  • This did work to generate GeoTIFFs and a few other files. Thanks! However, I can't generate the Ascii grid files I need. I tried using -of AAIGrid which is the type gdalinfo gives me for the source files, but I get a message saying that it's not recognized. – Btz Oct 21 '16 at 15:25

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