---
title: ES|QL ST_SIMPLIFY function
description:
url: https://www.elastic.co/elastic/docs-builder/docs/3256/reference/query-languages/esql/functions-operators/spatial-functions/st_simplify
products:
- Elasticsearch
---
# ES|QL ST_SIMPLIFY function
- Elastic Cloud Serverless: Preview
- Elastic Stack: Planned
## Syntax
## Parameters
Expression of type `geo_point`, `geo_shape`, `cartesian_point` or `cartesian_shape`. If `null`, the function returns `null`.
Tolerance for the geometry simplification, in the units of the input SRS
## Description
Simplifies the input geometry by applying the Douglas-Peucker algorithm with a specified tolerance. Vertices that fall within the tolerance distance from the simplified shape are removed. Note that the resulting geometry may be invalid, even if the original input was valid.
## Supported types
| geometry | tolerance | result |
|-----------------|-----------|-----------------|
| cartesian_point | double | cartesian_point |
| cartesian_point | float | cartesian_point |
| cartesian_point | integer | cartesian_point |
| cartesian_point | long | cartesian_point |
| cartesian_shape | double | cartesian_shape |
| cartesian_shape | float | cartesian_shape |
| cartesian_shape | integer | cartesian_shape |
| cartesian_shape | long | cartesian_shape |
| geo_point | double | geo_point |
| geo_point | float | geo_point |
| geo_point | integer | geo_point |
| geo_point | long | geo_point |
| geo_shape | double | geo_shape |
| geo_shape | float | geo_shape |
| geo_shape | integer | geo_shape |
| geo_shape | long | geo_shape |
## Example
```esql
ROW wkt = "POLYGON ((7.998 53.827, 9.470 53.068, 15.754 53.801, 16.523 57.160, 11.162 57.868, 8.064 57.445, 6.219 55.317, 7.998 53.827))"
| EVAL simplified = ST_SIMPLIFY(TO_GEOSHAPE(wkt), 0.7)
```
| wkt:keyword | simplified:geo_shape |
|-------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------|
| POLYGON ((7.998 53.827, 9.470 53.068, 15.754 53.801, 16.523 57.160, 11.162 57.868, 8.064 57.445, 6.219 55.317, 7.998 53.827)) | POLYGON ((9.47 53.068, 15.754 53.801, 16.523 57.16, 8.064 57.445, 6.219 55.317, 9.47 53.068)) |
### Diagrams
**Low tolerance keeps almost every vertex**
With a small tolerance, only collinear or near-collinear vertices are removed.
**Mid tolerance smooths out the bumps**
A tolerance of `0.2` is large enough to remove the small dents along each edge, leaving the underlying square.
**Simplifying a circle with tolerance 0.5**
Higher tolerances drop more vertices and the circle becomes a rough polygon.
**Simplifying a circle to an octagon**
Tolerance `1.0` reduces the circle to a regular octagon.
**Simplifying a coastline at moderate tolerance**
France's coastline simplified at tolerance `0.1` (roughly 10 km). Small bays and peninsulas survive but the coastline is noticeably smoother.
**Simplifying a coastline at coarse tolerance**
France's coastline simplified at tolerance `0.5` (roughly 50 km). Only the high-level shape of the country remains.
