<element name="rows" type="integer" minOccurs="0">
  <annotation>
    <documentation>The attribute rows gives the number of rows in the parameter grid.</documentation>
  </annotation>
</element>

<element name="columns" type="integer" minOccurs="0">
  <annotation>
    <documentation>The attribute columns gives the number of columns in the parameter grid.</documentation>
  </annotation>
</element>

<complexType name="AbstractGriddedSurfaceType">
  <annotation>
    <documentation>A gridded surface is a parametric curve surface derived from a rectangular grid in the parameter space. The rows from this grid are control points for horizontal surface curves; the columns are control points for vertical surface curves. The working assumption is that for a pair of parametric co-ordinates (s, t) that the horizontal curves for each integer offset are calculated and evaluated at "s". The defines a sequence of control points: cn(s) : s 1 .....columns From this sequence a vertical curve is calculated for "s", and evaluated at "t". In most cases, the order of calculation (horizontal-vertical vs. vertical-horizontal) does not make a difference. Where it does, the horizontal- vertical order shall be the one used. Logically, any pair of curve interpolation types can lead to a subtype of GriddedSurface. The following clauses define some most commonly encountered surfaces that can be represented in this manner.</documentation>
  </annotation>
  <complexContent>
    <extension base="gml:AbstractParametricCurveSurfaceType">
      <sequence>
        <group ref="gml:PointGrid">
          <annotation>
            <documentation>This is the double indexed sequence of control points, given in row major form. NOTE! There in no assumption made about the shape of the grid. For example, the positions need not effect a "21/2D" surface, consecutive points may be equal in any or all of the ordinates. Further, the curves in either or both directions may close.</documentation>
          </annotation>
        </group>
        <element name="rows" type="integer" minOccurs="0">
          <annotation>
            <documentation>The attribute rows gives the number of rows in the parameter grid.</documentation>
          </annotation>
        </element>
        <element name="columns" type="integer" minOccurs="0">
          <annotation>
            <documentation>The attribute columns gives the number of columns in the parameter grid.</documentation>
          </annotation>
        </element>
      </sequence>
    </extension>
  </complexContent>
</complexType>