  </h6>
<p>
            Returns true if the geometry is valid (in the OGC sense); furthermore,
            the following geometries are considered valid: multi-geometries with
            no elements, linear geometries containing spikes, areal geometries with
            duplicate (consecutive) points
          </p>
<h6>
<a name="geometry.reference.algorithms.is_valid.is_valid_2_with_message.h3"></a>
            <span class="phrase"><a name="geometry.reference.algorithms.is_valid.is_valid_2_with_message.hea