geos_union - ObjectVision/GeoDMS GitHub Wiki
Geometric functions > geos_union
- geos_union(polygon_data_item1, polygon_data_item2)
geos_union(polygon_data_item1, polygon_data_item2) results in a data item with the union of the two polygon arguments. The result contains, for each element, the combined area covered by either polygon argument.
The operator is applied element-by-element. Both domains need to match, or one of the arguments needs to be a parameter (void domain).
The geos_ prefix of the function name indicates that the implementation of the operator uses geos.
This operator is also automatically invoked by the + and | operators when used with fpoint or dpoint polygon data items.
- attribute polygon_data_item1 with a polygon value type
- attribute polygon_data_item2 with a polygon value type
The value types of both arguments must be compatible (same point type).
- The composition type of both arguments needs to be polygon.
- The domains of the two arguments must match, or one argument must have a void domain (parameter).
14.0
attribute<fpoint> geometry_union (district) := geos_union(district/geometry, municipality/geometry);
// equivalent to:
attribute<fpoint> geometry_union (district) := district/geometry + municipality/geometry;