docs/api/sql/Raster-Predicates/RS_DWithin.md

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# RS_DWithin

Introduction: Returns true if the raster or geometry on the left side is within `distance` **meters** of the raster or geometry on the right side. The convex hull of the raster is considered in the test. At least one of the two shape arguments must be a raster — for the geometry-only case use [`ST_DWithin`](../Predicates/ST_DWithin.md) instead.

Rules for testing spatial relationship:

- If the raster or geometry does not have a defined SRID, it is assumed to be in WGS84.
- Both sides are unconditionally projected to WGS84 before the test, so `distance` is **always** measured in meters regardless of the input CRS.
- The per-row test computes the **minimum geodesic distance** between the two shapes — the raster is represented by its convex hull, and the geodesic distance is measured between the closest pair of points on the two hulls (not centroid-to-centroid). Two raster footprints that overlap or touch therefore satisfy `RS_DWithin(a, b, 0)`, mirroring [`RS_Intersects`](RS_Intersects.md).

When used as a join condition, Sedona plans the join as an optimized distance join (`BroadcastIndexJoinExec` or `DistanceJoinExec`): each side's WGS84 envelope is computed, the distance-side envelope is expanded by `distance` meters using the Haversine polar-radius approximation (the same expansion `ST_DistanceSphere` uses), and the resulting envelopes drive an R-tree filter before the per-row `RS_DWithin` check refines the result.

Format:

`RS_DWithin(raster: Raster, geom: Geometry, distance: Double)`

`RS_DWithin(geom: Geometry, raster: Raster, distance: Double)`

`RS_DWithin(raster0: Raster, raster1: Raster, distance: Double)`

Return type: `Boolean`

Since: `v1.9.1`

SQL Example

```sql
SELECT RS_DWithin(
    RS_MakeEmptyRaster(1, 20, 20, 2, 22, 1),
    ST_SetSRID(ST_PolygonFromEnvelope(30, 30, 40, 40), 4326),
    5000000.0  -- 5 000 km, in meters
) AS within_5000km
```

Output:

```
+-------------+
|within_5000km|
+-------------+
|         true|
+-------------+
```

Using `RS_DWithin` as a distance-join condition (`distance` in meters):

```sql
SELECT r.id, p.id
FROM rasters r
JOIN points p ON RS_DWithin(r.raster, p.geom, 1000)  -- within 1 km
```