bg_union_polygon

geometric-functions bg_union_polygon

syntax

  • bg_union_polygon(polygon_data_item)
  • bg_union_polygon(polygon_data_item, relation)

description

bg_union_polygon(polygon_data_item, partitioning) results in an attribute with all polygons from polygon_data_item, grouped by the argument relation.

Lines between adjacent polygons within each group are removed.

The domain-unit of the resulting attribute is the values-unit of the relation.

In other GIS software, the term dissolve is often used for this operation.

conditions

  1. The composition type of the polygon_data_item item needs to be a polygon with an ipoint, spoint, fpoint, or dpoint value-type.
  2. The domain unit of the polygon_data_item item must be of value type uint32.
  3. The domain unit of arguments polygon_data_item and relation must match.
  4. The order of points in the polygon_data_item needs to be clockwise for exterior bounds and counterclockwise for holes in polygons (right-hand rule).

function type

  • bg_union_polygon(D->P) -> void->P
  • bg_union_polygon(D->P, part_rel: D->R) -> R->P

where P is a GeoDms point type with signed integer coordinates, i.e. 16, 32, or 64-bit signed integers, D is the domain of the argument, and R is the values unit of the partitioning part_rel.

since version

15.6.0

example 

parameter<fpoint> geometry (polygon) := bg_union_polygon(district/geometry);
attribute<fpoint> geometry (polygon, region) := bg_union_polygon(district/geometry, district/region_rel);

see also