### 12.15.2 Argument Handling by Spatial Functions

Spatial values, or geometries, have the properties described at
Section 11.5.2.2, “Geometry Class”. The following discussion
lists general spatial function argument-handling characteristics.
Specific functions or groups of functions may have additional
argument-handling characteristics, as discussed in the sections
where those function descriptions occur.

Spatial functions are defined only for valid geometry values. If
an invalid geometry is passed to a spatial function, the result is
undefined.

The Spatial Reference Identifier (SRID) of a geometry identifies
the coordinate space in which the geometry is defined. In MySQL,
the SRID value is an integer associated with the geometry value.
However, all calculations are done assuming SRID 0, representing
cartesian (planar) coordinates, regardless of the actual SRID
value. In the future, calculations may use the specified SRID
values. To ensure SRID 0 behavior, create geometries using SRID 0.
SRID 0 is the default for new geometries if no SRID is specified.

The maximum usable SRID value is
2^{32}−1. If a larger value is
given, only the lower 32 bits are used.

Geometry values produced by any spatial function inherit the SRID
of the geometry arguments.