# **Bg_simplify_polygon**

*geometric-functions bg_simplify_polygon*

## syntax

- bg_simplify_polygon(
*polygon_data_item*,*simplifyfactor*)

## description

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

- attribute
*polygon_data_item*with an point value-type - parameter simplifyfactor with a float64 value type

## conditions

- The composition type type of the
*polygon_data_item*item needs to be polygon. - 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

7.409

## example

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