<simpleType name="PositiveDirectionEnumType">
  <restriction base="string">
    <enumeration value="increasing">
      <annotation>
        <documentation>Positive follows the coordinate order, from the first to the last coordinate. This is the standard convention.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="downward">
      <annotation>
        <documentation>Label for positive being downward (deeper), common for boreholes where the first coordinate is the collar and the last is the bottom of the hole.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="upward">
      <annotation>
        <documentation>Label for positive being upward (shallower), for example for core logged from bottom to top, or for elevation-based referencing.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="forward">
      <annotation>
        <documentation>Label for horizontal features: positive is the forward direction of the survey or alignment, common for transects, pipelines and tracklines.</documentation>
      </annotation>
    </enumeration>
  </restriction>
</simpleType>