User's Guide and Reference

Points

A point is a zero-dimensional geometry that occupies a single location in coordinate space. A point includes an X coordinate and a Y coordinate that define this location. It can also include a Z coordinate and a measure.

A point is simple and has a NULL boundary. Points are often used to define features such as oil wells, landmarks, and elevations.

Functions that operate solely on the point subclass:

ST_Point

Takes an X coordinate, its associated Y coordinate, and the identifier of the spatial reference system to which these coordinates belong, and returns the point that the coordinates define. For more information, see ST_Point.

ST_CoordDim

Returns a value that denotes what coordinates a point contains, and whether it also contains a measure. This value is called a coordinate dimension. Possible coordinate dimensions are:

2

The point consists of an X coordinate and a Y coordinate.

3

The point consists of an X coordinate, a Y coordinate, and a Z coordinate.

4

The point consists of an X coordinate, a Y coordinate, a Z coordinate, and a measure.

For more information, see ST_CoordDim.

ST_PointFromText

Takes an OGC well-known text (WKT) representation of a point and returns the point. For more information, see ST_PointFromText.

ST_X

Returns an ST_Point data type's X coordinate value as a double precision number. For more information, see ST_X.

ST_Y

Returns an ST_Point data type's Y coordinate value as a double precision number. For more information, see ST_Y.

Z

Returns an ST_Point data type's Z coordinate value as a double precision number. For more information, see Z.

M

Returns an ST_Point data type's measure as a double precision number. For more information, see M.