geos_simplify_multi_polygon

Geometric functions > geos_simplify_multi_polygon

syntax

  • geos_simplify_multi_polygon(polygon_data_item, simplifyfactor)

description

geos_simplify_multi_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 into 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 uses the metric of the coordinate system.

The geos_ prefix of the function name indicates that the implementation of the operator uses geos.

Only dpoint (double precision) coordinates are supported. For fpoint coordinates, use bg_simplify_multi_polygon.

applies to

Since GeoDMS 20.23.1 simplifyfactor must be a parameter with a defined value of 0 or more. An attribute with a value per element was accepted and the value of the first element applied to every element; it now stops with the tolerance must be a parameter. A negative or null value stops with the tolerance must be a defined value of 0 or more; before, a negative value gave an error of the geos library for the geos_ operators, and a null an undefined result for the bg_ operators.

conditions

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

since version

example 

attribute<dpoint> geometry_simplified (district) := geos_simplify_multi_polygon(district/geometry, 10.0);

see also