is_valid

Tests to see if a geometry is valid according to the OGC definition. Tests to see if a geometry satisfies the OGC validity assertions. The validity criteria are:

• a geometry of type simple-point, simple-line, complex-point or complex-line is valid

• a simple geometry is valid if the outer ring encloses any inner rings, no ring self-intersects another ring or self-touches and no ring intersects another ring. A ring may touch another ring at a point, but must not cross it or have any line-work in common. A ring must not contain duplicate points

Number of parameters: 1.

Parameter 1 - any geometry.

Returns: a Boolean value, true if the geometry is valid according to the OGC definition and false if it is not.