<simpleType name="UncertaintyRepresentationEnumType">
  <restriction base="string">
    <enumeration value="plus-minus">
      <annotation>
        <documentation>Uncertainty values represent upper and/or lower bounds expressed as plus and/or minus offsets from the reported coordinate value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="standard deviation">
      <annotation>
        <documentation>Uncertainty values represent one standard deviation (1σ) of a presumed statistical distribution.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="confidence interval">
      <annotation>
        <documentation>Uncertainty values represent bounds associated with a stated confidence level.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="maximum error">
      <annotation>
        <documentation>Uncertainty values represent the maximum expected deviation from the reported coordinate value.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="estimated">
      <annotation>
        <documentation>Uncertainty values are approximate estimates where no formal statistical model is available.</documentation>
      </annotation>
    </enumeration>
  </restriction>
</simpleType>