<xs:simpleType name="VerticalDatumType">
  <xs:annotation>
    <xs:appinfo>
      <mdr:definition>MSL - Mean Sea Level; MSL is understood to be functionally equivalent to the EGM-96 (Earth Gravity Model 1996) Geoid for the purposes of search expressions. AGL - Above Ground Level HAE - Height Above Ellipsoid</mdr:definition>
    </xs:appinfo>
  </xs:annotation>
  <xs:restriction base="xs:string">
    <xs:enumeration value="MSL"/>
    <xs:enumeration value="AGL"/>
    <xs:enumeration value="HAE"/>
  </xs:restriction>
</xs:simpleType>