geometric-functions bg_simplify_polygon


  • bg_simplify_polygon(polygon_data_item, simplifyfactor)


bg_simplify_polygon(polygon_data_item, simplifyfactor) results in a data-item with the geometry of the polygon_data_item, in which the geometric structure is simplified. Near points are combined to a single point. What is near is configured with the simplifyfactor, a parameter indicating for which distance points are combined. No metric needs to be configured for the simplifyfactor, it is using the metric of the coordinate-system.

The bg_ prefix of the function name indicates that the implementation of operator uses boost geometry library, more specifically, the simplify function.

applies to


  1. The composition type type of the polygon_data_item item needs to be polygon.
  2. The order of points in the polygon_data_item needs to be clockwise for exterior bounds and counter clockwise for holes in polygons (right-hand-rule).

This function may result in losing the adjacency of polygons and in overlapping polygons, as shown in the figure above. We advice to be careful with functions like point_in_polygon on the resulting geometries. If you want to simplify your polygons while maintaining the topology, use the poly-to-grid-to-(simplified)-polygon script.

since version



attribute<fpoint> geometry_simplified (polygon, city) := bg_simplify_polygon(city/geometry, 10.0);

see also: