<simpleType name="ArrayTypeEnumType">
  <restriction base="string">
    <enumeration value="wenner">
      <annotation>
        <documentation>Four electrodes in a line at equal separation "a": the outer pair injects current and the inner pair measures potential. Structured through diggs:ResistivityReadingType/electrodeSpacing.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="schlumberger">
      <annotation>
        <documentation>A closely spaced potential electrode pair at the center of a more widely spaced current electrode pair, the spacing of which increases progressively in a sounding. Structured through diggs:ResistivityReadingType/currentElectrodeSeparation and potentialElectrodeSeparation.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="dipole dipole">
      <annotation>
        <documentation>A current dipole and a potential dipole of equal length, offset from each other by a multiple (n) of that length, both moved together as the array is stepped. Structured through diggs:ResistivityReadingType/dipoleLength and nFactor.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="pole dipole">
      <annotation>
        <documentation>One current electrode and a potential dipole, the second current electrode being placed far enough away to be treated as at infinity; the dipole is separated from the current pole by a multiple of the dipole length.</documentation>
      </annotation>
    </enumeration>
    <enumeration value="gradient">
      <annotation>
        <documentation>Two current electrodes at a fixed wide spacing, with a potential dipole moved between them.</documentation>
      </annotation>
    </enumeration>
  </restriction>
</simpleType>