## Name

ST_CoverageSimplify — Fonction window qui simplifie les bords d'une couverture polygonale.

## Synopsis

`geometry ST_CoverageSimplify(`geometry winset geom, float8 tolerance, boolean simplifyBoundary = true`)`;

## Description

A window function which simplifies the edges of polygons in a polygonal coverage. The simplification preserves the coverage topology. This means the simplified output polygons are consisent along shared edges, and still form a valid coverage.

The simplification uses a variant of the Visvalingam–Whyatt algorithm. The `tolerance` parameter has units of distance, and is roughly equal to the square root of triangular areas to be simplified.

Pour simplifier uniquement les bords "internes" de la couverture (ceux qui sont partagés par deux polygones), définissez le paramètre `simplifyBoundary` à false.

 If the input is not a valid coverage there may be unexpected artifacts in the output (such as boundary intersections, or separated boundaries which appeared to be shared). Use ST_CoverageInvalidEdges to determine if a coverage is valid.

Availability: 3.4.0

Requires GEOS >= 3.12.0

## Exemples

 Input coverage Simplified coverage
```WITH coverage(id, geom) AS (VALUES
(1, 'POLYGON ((160 150, 110 130, 90 100, 90 70, 60 60, 50 10, 30 30, 40 50, 25 40, 10 60, 30 100, 30 120, 20 170, 60 180, 90 190, 130 180, 130 160, 160 150), (40 160, 50 140, 66 125, 60 100, 80 140, 90 170, 60 160, 40 160))'::geometry),
(2, 'POLYGON ((40 160, 60 160, 90 170, 80 140, 60 100, 66 125, 50 140, 40 160))'::geometry),
(3, 'POLYGON ((110 130, 160 50, 140 50, 120 33, 90 30, 50 10, 60 60, 90 70, 90 100, 110 130))'::geometry),
(4, 'POLYGON ((160 150, 150 120, 160 90, 160 50, 110 130, 160 150))'::geometry)
)
SELECT id, ST_AsText(ST_CoverageSimplify(geom, 30) OVER ())
FROM coverage;

id |               st_astext
----+---------------------------------------
1 | POLYGON ((160 150, 110 130, 50 10, 10 60, 20 170, 90 190, 160 150), (40 160, 66 125, 90 170, 40 160))
2 | POLYGON ((40 160, 66 125, 90 170, 40 160))
3 | POLYGON ((110 130, 160 50, 50 10, 110 130))
3 | POLYGON ((160 150, 160 50, 110 130, 160 150))
```