Search code examples
geojsontopojsonogr2ogr

Combining GeoJSON Features

I have a large (200MB) geoJSON file that has a lot of complex polygons and multipolygons. A very truncated example is at https://gist.github.com/jinky32/81f61e1fc118822ba103?short_path=d16949b

As you can see this file is comprised of polygons and multipolygons that have a String property of either 1 or 2. Below is an example of how these shapes look on mapshaper.org when highlighting a multipolygon of either value in the same tile (essentially c.90+% of this tile is made up of a multipolygon with one value or the other)

String value 1 ----- ---- ----- String Value 2

I do not need to differentiate between these different values and polygons / multipolygons with a String value of either 1 or 2 can be combined together which I hope will reduce the file size.

Can anyone advise how I can achieve this - preferably with a cli tool?

Solution

  • Answer is to use ogr2ogr:

    ogr2ogr -f "GeoJSON" -dialect sqlite -sql "select st_union(geometry) as geometry from OGRGeoJSON where string in ('1','2')" gj_union_test.json geojsontest.json