User's Guide and Reference

Multipoints

A multipoint is a collection of points, and like its elements, it has a dimension of 0. A multipoint is simple if none of its elements occupy the same coordinate space. The boundary of a multipoint is NULL. Multipoints may be used to define phenomena such as aerial broadcast patterns and incidents of an epidemic outbreak.

Functions that operate on multipoints:

ST_NumGeometries

Takes a homogeneous collection and returns the number of base geometry elements it contains. For more information, see ST_NumGeometries.

ST_GeometryN

Takes a homogeneous collection and an index and returns the nth base geometry. For more information, see ST_GeometryN.