ST_Covers
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## Name

ST_Covers — Return true if no points of raster rastB lie outside raster rastA.

## Synopsis

`boolean ST_Covers(` raster rastA , integer nbandA , raster rastB , integer nbandB `)`;

`boolean ST_Covers(` raster rastA , raster rastB `)`;

## Description

Raster rastA covers rastB if and only if no points of rastB lie in the exterior of rastA. If the band number is not provided (or set to NULL), only the convex hull of the raster is considered in the test. If the band number is provided, only those pixels with value (not NODATA) are considered in the test.

This function will make use of any indexes that may be available on the rasters.

To test the spatial relationship of a raster and a geometry, use ST_Polygon on the raster, e.g. ST_Covers(ST_Polygon(raster), geometry) or ST_Covers(geometry, ST_Polygon(raster)).

Availability: 2.1.0

## Examples

    SELECT r1.rid, r2.rid, ST_Covers(r1.rast, 1, r2.rast, 1) FROM dummy_rast r1 CROSS JOIN dummy_rast r2 WHERE r1.rid = 2;

     rid | rid | st_covers
    -----+-----+-----------
       2 |   1 | f
       2 |   2 | t

## See Also

ST_Intersects, ST_CoveredBy

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