<xs:simpleType name="angleType">
  <xs:annotation>
    <xs:documentation>The angle units (can be radians, gons, mils, deg or dddmmsss)</xs:documentation>
  </xs:annotation>
  <xs:restriction base="xs:NMTOKEN">
    <xs:enumeration value="radians"/>
    <xs:enumeration value="grad_gons"/>
    <xs:enumeration value="mils"/>
    <xs:enumeration value="dec_deg"/>
    <xs:enumeration value="dddmmsss"/>
    <xs:enumeration value="arcsec"/>
  </xs:restriction>
</xs:simpleType>