Borehole Measurement Type Borehole measurements values are usually given with respect to datums. The datums may be different for a logger than a driller. There is also the specification of a permanent datum. bhMeasureType extBHMeasureType refinedBHMeasureType refinedExtBHMeasureType POSC 1.0 driller This represents the reference point that is used as a datum for depth measurements relating to drilling. This datum generally applies to measurements in a wellbore. logger This represents the reference point that is used as a datum for depth measurements related to well logs and the logging jobs. This datum generally applies to measurements in a wellbore. permanent This represents the datum for the well. In general, the elevation of the well is the elevation of this point. Also, true vertical depths of points in and near the wellbore(s) are often measured with respect to this datum. When applied to a wellbore, the permanent datum is the zero point for measuring the kickoff point. It is assumed that the kickoff point is given in measured depth from the permanent wellbore datum.