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# ST_Snap

Introduction: Snaps the vertices and segments of the `input` geometry to `reference` geometry within the specified `tolerance` distance. The `tolerance` parameter controls the maximum snap distance.

If the minimum distance between the geometries exceeds the `tolerance`, the `input` geometry is returned unmodified. Adjusting the `tolerance` value allows tuning which vertices should snap to the `reference` and which remain untouched.

Return type: `Geometry`

Since: `v1.6.0`

Format: `ST_Snap(input: Geometry, reference: Geometry, tolerance: double)`

Input geometry:

![ST_Snap base example](../../../image/st_snap/st-snap-base-example.png "ST_Snap base example")

SQL Example:

```sql
SELECT
    ST_Snap(poly, line, ST_Distance(poly, line) * 1.01) AS polySnapped FROM (
        SELECT ST_GeomFromWKT('POLYGON ((236877.58 -6.61, 236878.29 -8.35, 236879.98 -8.33, 236879.72 -7.63, 236880.35 -6.62, 236877.58 -6.61), (236878.45 -7.01, 236878.43 -7.52, 236879.29 -7.50, 236878.63 -7.22, 236878.76 -6.89, 236878.45 -7.01))') as poly,
            ST_GeomFromWKT('LINESTRING (236880.53 -8.22, 236881.15 -7.68, 236880.69 -6.81)') as line
)
```

Output:

![ST_Snap applied example](../../../image/st_snap/st-snap-applied.png "ST_Snap applied example")

```
POLYGON ((236877.58 -6.61, 236878.29 -8.35, 236879.98 -8.33, 236879.72 -7.63, 236880.69 -6.81, 236877.58 -6.61), (236878.45 -7.01, 236878.43 -7.52, 236879.29 -7.5, 236878.63 -7.22, 236878.76 -6.89, 236878.45 -7.01))
```