<simpleType name="SurfaceInterpolationType">
  <annotation>
    <documentation>gml:SurfaceInterpolationType is a list of codes that may be used to identify the interpolation mechanisms specified by an application schema.</documentation>
  </annotation>
  <restriction base="string">
    <enumeration value="none"/>
    <enumeration value="planar"/>
    <enumeration value="spherical"/>
    <enumeration value="elliptical"/>
    <enumeration value="conic"/>
    <enumeration value="tin"/>
    <enumeration value="parametricCurve"/>
    <enumeration value="polynomialSpline"/>
    <enumeration value="rationalSpline"/>
    <enumeration value="triangulatedSpline"/>
  </restriction>
</simpleType>