# ST\_Simplify

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ST\_Simplify is available from [MariaDB 12.0](https://app.gitbook.com/s/aEnK0ZXmUbJzqQrTjFyb/community-server/release-notes-mariadb-12.0-rolling-releases/what-is-mariadb-120).
{% endhint %}

## Syntax

```sql
ST_Simplify(g, max_distance)
```

## Description

Takes as input a geometry (g) and a double (max\_distance). It applies the [Ramer–Douglas–Peucker algorithm](https://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm) on `g` and returns the resulting geometry.

The goal of the Douglas-Peucker algorithm is to provide generalized simplifications by returning a geometry that is similar to `g` but uses only a subset of points. To perform the simplification, all the vertices that are shorter than `max_distance` are removed.

The algorithm may produce self-intersections and therefore result in invalid geometries. [ST\_IsValid](https://mariadb.com/docs/server/reference/sql-statements/geometry-constructors/miscellaneous-gis-functions/st_isvalid) can be used to test validity of the result.

If the max\_distance is not positive or is `NULL`, an `ER_WRONG_ARGUMENT` will occur.

## Examples

```sql
SELECT ST_AsText(ST_Simplify(ST_GeomFromText('LINESTRING(0 0,0 2,2 2,2 4,4 4,4 6,6 6)'), 0.5));
+-----------------------------------------------------------------------------------------+
| ST_AsText(ST_Simplify(ST_GeomFromText('LINESTRING(0 0,0 2,2 2,2 4,4 4,4 6,6 6)'), 0.5)) |
+-----------------------------------------------------------------------------------------+
| LINESTRING(0 0,0 2,2 2,2 4,4 4,4 6,6 6)                                                 |
+-----------------------------------------------------------------------------------------+

SELECT ST_AsText(ST_Simplify(ST_GeomFromText('LINESTRING(0 0,0 2,2 2,2 4,4 4,4 6,6 6)'), 1));  
+---------------------------------------------------------------------------------------+
| ST_AsText(ST_Simplify(ST_GeomFromText('LINESTRING(0 0,0 2,2 2,2 4,4 4,4 6,6 6)'), 1)) |
+---------------------------------------------------------------------------------------+
| LINESTRING(0 0,0 2,2 2,2 4,6 6)                                                       |
+---------------------------------------------------------------------------------------+
```

## See Also

* [Geometry Constructors](https://mariadb.com/docs/server/reference/sql-statements/geometry-constructors)
* [ST\_AsText](https://mariadb.com/docs/server/reference/sql-statements/geometry-constructors/wkt/st_astext)
* [ST\_GeomFromText](https://mariadb.com/docs/server/reference/sql-statements/geometry-constructors/wkt/st_geomfromtext)

<sub>*This page is licensed: CC BY-SA / Gnu FDL*</sub>

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