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     <h4 class="title">
      <a name="gis-class-surface">
      </a>
      13.4.2.6 Surface Class
     </h4>
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  <p>
   A
   <code class="literal">
    Surface
   </code>
   is a two-dimensional geometry. It
          is a noninstantiable class. Its only instantiable subclass is
   <code class="literal">
    Polygon
   </code>
   .
  </p>
  <p>
   <span class="bold">
    <strong>
     <code class="literal">
      Surface
     </code>
     Properties
    </strong>
   </span>
  </p>
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   <ul class="itemizedlist" style="list-style-type: disc; ">
    <li class="listitem">
     <p>
      A
      <code class="literal">
       Surface
      </code>
      is defined as a
              two-dimensional geometry.
     </p>
    </li>
    <li class="listitem">
     <p>
      The OpenGIS specification defines a simple
      <code class="literal">
       Surface
      </code>
      as a geometry that consists of
              a single
      <span class="quote">
       “
       <span class="quote">
        patch
       </span>
       ”
      </span>
      that is associated with a
              single exterior boundary and zero or more interior
              boundaries.
     </p>
    </li>
    <li class="listitem">
     <p>
      The boundary of a simple
      <code class="literal">
       Surface
      </code>
      is the
              set of closed curves corresponding to its exterior and
              interior boundaries.
     </p>
    </li>
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