User's Guide and Reference

Envelope

The envelope of a geometry is the bounding geometry formed by the minimum and maximum (X,Y) coordinates. With the following exceptions, the envelopes of most geometries form a boundary rectangle:

• The envelope of a point is the point itself, because its minimum and maximum coordinates are the same.
• The envelope of a horizontal or vertical linestring is a linestring represented by the boundary (the endpoints) of the source linestring.

The ST_Envelope function takes a geometry and returns a bounding geometry, which represents its envelope. For more information, see ST_Envelope.