Calculating common area between shapefiles using GDAL

Question

I'm looking for a way to get the intersection area between my shapefiles. Basically, I got three shapefiles from my .tif files like this:

gdaltindex a.shp a.tif
gdaltindex b.shp b.tif
gdaltindex c.shp c.tif

This way I got the area of my .tif files. Now I would like to get a new shapefile via intersection. I thought about using gdalwarp, for example like this:

gdalwarp -cutline intersection.shp a.tif a_intersection.tif
gdalwarp -cutline intersection.shp b.tif b_intersection.tif
gdalwarp -cutline intersection.shp c.tif c_intersection.tif

but i can't figure out how to get the intersection.shp file I can do it via QGIS, but would like to do it directly from GDAL. How can I do this?

Answer 1

I don't think you can do this with GDAL, but you can create the intersection shapefile with mapshaper's -mosaic.

With the following, you

• read in all shapefiles
• mosaic them together, so all overlaps are converted into their own feature
• calculate the number of overlaps for each feature
• sort the features, and get the one with the most overlaps

mapshaper -i *.shp combine-files -merge-layers -mosaic calc='OVERLAPS=count()' -sort 'OVERLAPS' descending -filter 'this.id==0' -o intersection.shp

To simplify things, you could use

gdaltindex footprints.shp *.tif
mapshaper footprints.shp -mosaic calc='OVERLAPS=count()' -sort 'OVERLAPS' descending -filter 'this.id==0' -o intersection.shp