QGIS – Inverting Polygons in Shapefile Geometry

geometrypolygonqgisshapefile

I have a Shapefile with Polygon features representing the world's land areas (continents, islands).

Is it possible to invert these, and get a geometry that represents the world's oceans and seas?

So the original land Polygons need to become rings in a single global Polygon that covers the planet.

Basically, I'm looking for something like Select > Inverse in Photoshop.

I am using QGIS.

Best Answer

You can do this using the following steps:

1- In QGIS go to Vector > Research Tools > Polygon From Layer Extent. Use the World's Land area as Input File. Choose the Desired name for the output file name of extent layer. This will create a new vector layer covering the Whole Land area.

2- Use Geoprocessing Tools > Difference: Use the extent layer created in step one as input file and world's land area as difference file. Then You will get an opposite shapefile which represents the ocean.

Related Question