<simpleType name="LoadTestReferenceSystemEnumType">
  <restriction base="string">
    <enumeration value="independent reference beam">
      <annotation>
        <documentation>Displacement measured against a fixed reference beam supported clear of the reaction system and of any ground disturbed by the test.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="optical survey">
      <annotation>
        <documentation>Displacement measured by optical or total-station survey referenced to a fixed benchmark independent of the reaction system.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="satellite positioning">
      <annotation>
        <documentation>Displacement measured by satellite positioning (GNSS) referenced to a fixed benchmark.</documentation>
      </annotation>
    </enumeration>
  </restriction>
</simpleType>