The OpenGIS specification defines the following functions. They
test the relationship between two geometry values
g1 and g2, using precise
object shapes. The return values 1 and 0 indicate true and
false, respectively.
Returns 1 if g1 spatially crosses
g2. Returns
NULL if g1 is a
Polygon or a
MultiPolygon, or if
g2 is a Point
or a MultiPoint. Otherwise, returns 0.
The term spatially crosses denotes a spatial relation between two given geometries that has the following properties:
The two geometries intersect
Their intersection results in a geometry that has a dimension that is one less than the maximum dimension of the two given geometries
Their intersection is not equal to either of the two given geometries
Returns 1 or 0 to indicate whether
g1 spatially touches
g2. Two geometries
spatially touch if the interiors of the
geometries do not intersect, but the boundary of one of the
geometries intersects either the boundary or the interior of
the other.