STGeomFromWKB

ST_GeomFromWKB is a spatial database function that converts a Well-Known Binary (WKB) representation of a geometry into a geometry object. It is commonly used in PostGIS and related spatial extensions to translate binary geometry data into usable geometric types such as POINT, LINESTRING, and POLYGON. The function reads WKB data and returns the corresponding geometry in the database’s geometry type system.

Input to ST_GeomFromWKB is typically a binary value that encodes a geometry in WKB format. In standard WKB, the coordinate reference system (CRS) is not embedded; if the input uses Extended Well-Known Binary (EWKB), an embedded SRID may be present and used to set the geometry’s spatial reference. Some implementations also provide an overload that accepts a second integer parameter to assign a specific SRID to the resulting geometry when the WKB does not contain one.

Syntax generally includes variants such as ST_GeomFromWKB(wkb) and ST_GeomFromWKB(wkb, srid). The exact syntax can vary by version or database, so users should consult their system’s documentation. Typical usage involves supplying a bytea value representing the WKB, with an optional SRID for non-EWKB input.

Notes on behavior: ST_GeomFromWKB validates the input and will raise an error for invalid WKB data. It preserves or assigns dimensionality (2D, 3D, etc.) according to the input, and may handle Z and M coordinates if present. For inputs containing an SRID, EWKB behavior will apply that SRID automatically; otherwise the optional SRID argument can be used to set it.

See also: ST_GeomFromEWKB, WKB, EWKB, ST_AsBinary, SRID.