Calculating Satellite Image Boundaries using Open Source Tools

footprintgdalpyqgisqgis-plugins

I need to create the polygon outlines of several single layer raster images, not the extent/bounding box, but the area without the nodata values, as shown here: Creating shapefile showing footprints of Rasters?.

In the answer to the question above, the Image Boundary plugin was mentioned, however, I don't find it in the QGIS 1.8.0 Lisboa, running on Ubuntu.

Is the tool still available?

If not, is there a way to do this using opensource tools, either gdal, R, QGIS, GRASS, or similar, not with ArcMap?

Best Answer

I finally found a way to do this:

step 1: gdalwarp -dstnodata 0 -dstalpha -of GTiff foo1 foo2

This does two important things: it sets the destination No Data (outside border) values to 0, and it creates an alpha band.

step 2: gdal_polygonize.py foo2 -b 2 -f "ESRI Shapefile" foo3

The second step uses the alpha band (band 2), created in step 1, and creates a shapefile from that band.

This can then easily be scripted in a bash script, if you have many images, to create exact outlines for.  

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