              linear (e.g. linestring)
                    </p>
                  </td>
<td>
                    <p>
                      Returns zero
                    </p>
                  </td>
</tr>
<tr>
<td>
                    <p>
                      areal (e.g. polygon)
                    </p>
                  </td>
<td>
                    <p>
                      Returns the perimeter
                    </p>
                  </td>
</tr>
</tbody>
</table></div>
<h6>
<a name="geometry.refe