covers

Returns true if geometry b lies in geometry a.

Geometry a contains geometry b if all points of b are in the interior or at the boundary of a.

If either geometry is empty, returns false.

covers is the converse of coveredBy: covers(a, b) === coveredBy(b, a).

warning

Do not use this function with invalid geometries. You will get unexpected results.

Parameters

Name	Type	Description
a	Geometry | Prepared<Geometry>	First geometry
b	Geometry	Second geometry

Returns

boolean

true if geometry a covers geometry b

Throws

• GEOSError on unsupported geometry types (curved)

See also

• coveredBy converse of covers
• contains less inclusive covers
• containsProperly less inclusive contains
• prepare improves performance of repeated calls against a single geometry

Examples

differences with 'contains'

const a = lineString([ [ 0, 13 ], [ 4, 15 ], [ 2, 10 ] ]);
const b = point([ 2, 10 ]);
const ab_contain = contains(a, b); // false - no interior point in common
const ab_cover = covers(a, b); // true

const c = polygon([ [ [ 10, 13 ], [ 14, 15 ], [ 15, 10 ], [ 10, 13 ] ] ]);
const d = lineString([ [ 10, 13 ], [ 14, 15 ], [ 15, 10 ] ]);
const cd_contain = contains(c, d); // false - no interior point in common
const cd_cover = covers(c, d); // true

const a = lineString([ [ 0, 13 ], [ 4, 15 ], [ 2, 10 ] ]); const b = point([ 2, 10 ]); const ab_contain = contains(a, b); // false - no interior point in common const ab_cover = covers(a, b); // true const c = polygon([ [ [ 10, 13 ], [ 14, 15 ], [ 15, 10 ], [ 10, 13 ] ] ]); const d = lineString([ [ 10, 13 ], [ 14, 15 ], [ 15, 10 ] ]); const cd_contain = contains(c, d); // false - no interior point in common const cd_cover = covers(c, d); // true