Bg_simplify_linestring

Geometric functions bg_simplify_linestring

syntax

  • bg_simplify_linestring(arc_data_item, simplifyfactor)

description

bg_simplify_linestring(arc_data_item, simplifyfactor) results in a data item with the geometry of the arc_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 uses the Metric of the Coordinate system.

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

applies to

conditions

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

since version

8.031

performance

O(n * k) where n = number of arcs and k = average vertices per arc. Uses Douglas-Peucker algorithm. Output size depends on simplifyfactor relative to geometry detail.

example 

attribute<fpoint> geometry_simplified (polygon, district) := bg_simplify_linestring(road/geometry, 10.0);

see also