ST_Expand Signature GEOMETRY ST_Expand(GEOMETRY geom, DOUBLE deltaX, DOUBLE deltaY); Description Returns a Geometry’s envelope expanded by delta X and delta Y. Both positive and negative distances are supported. Examples SELECT ST_Expand('POINT(4 4)', 5, 2); -- Answer: POLYGON((-1 2, -1 6, 9 6, 9 2, -1 2)) SELECT ST_Expand('LINESTRING(3 2, 7 5, 2 7)', 2, 1); -- Answer: POLYGON((0 1, 0 8, 9 8, 9 1, 0 1)) SELECT ST_Expand('POLYGON((0.5 1, 0.5 7, 1.5 7, 1.5 1, 0.5 1))', 5, -1); -- ANswer: POLYGON((-4.5 2, -4.5 6, 6.5 6, 6.5 2, -4.5 2)) -- In this example, |deltaY| > ymax-ymin, so ST_Expand uses a deltaY -- of (ymax-ymin)/2. SELECT ST_Expand('POLYGON((0.5 1, 0.5 7, 1.5 7, 1.5 1, 0.5 1))', 5, -10); -- Answer: LINESTRING(-4.5 4, 6.5 4) SELECT ST_Expand('GEOMETRYCOLLECTION( LINESTRING(3 2, 7 5, 2 7), POINT(10 10), POLYGON((0.5 0, 0.5 7, 1.5 7, 1.5 1, 0.5 0)))', 2, 2); -- Answer: POLYGON((-1.5 -2, -1.5 12, 12 12, 12 -2, -1.5 -2)) See also ST_Buffer Source code Back Next