The functions given below are the ones which a user of PostGIS is likely to need. There are other functions which are required support functions to the PostGIS objects which are not of use to a general user.
Returns the geometry in the OGC "well-known-binary" format, using the endian encoding of the server on which the database is running. This is useful in binary cursors to pull data out of the database without converting it to a string representation.
Returns '2' if the geometry is two dimensional and '3' if the geometry is three dimensional.
Returns a POLYGON representing the bounding box of the geometry.
Returns the type of the geometry. Eg: LINESTRING, POLYGON, MULTIPOINT, etc.
Find and return the X coordinate of the first point in the geometry. Return NULL if there is no point in the geometry.
Find and return the Y coordinate of the first point in the geometry. Return NULL if there is no point in the geometry.
Find and return the Z coordinate of the first point in the geometry. Return NULL if there is no point in the geometry.
Find and return the number of points in the first linestring in the geometry. Return NULL if there is no linestring in the geometry.
Return the N'th point in the first linestring in the geometry. Return NULL if there is no linestring in the geometry.
Return the exterior ring of the first polygon in the geometry. Return NULL if there is no polygon in the geometry.
Return the number of interior rings of the first polygon in the geometry. Return NULL if there is no polygon in the geometry.
Return the N'th interior ring of the first polygon in the geometry. Return NULL if there is no polygon in the geometry.
If geometry is a GEOMETRYCOLLECTION return the number of geometries, otherwise return NULL.
Return the N'th geometry if the geometry is a GEOMETRYCOLLECTION. Otherwise, return NULL.