union

Returns the union of two or more geometries.

Any point that lies in any of the input geometries will also lie in the returned geometry.

Parameter 1 - any geometry.

Parameter 2 - another geometry to combine with the first.

Parameter etc. (Optional) - additional geometries to add to the union.

Returns: a geometry equal to the union of all the input geometries.

Note: This function does not fully support 3D geometries. Any 3D geometries will be projected down to 2 dimensions.