The terrestrial approach procedure may include DME ranges from the threshold, missed approach point or other reference, such as the beacon. The GPS may give distance guidance to a different point, such as the Aerodrome Reference Point. Pilots should be aware of any differences in the distance information given to step-down fixes and/or the MAP, as this has the potential for catastrophic error.
In Australia, GPS-flown VOR or NDB approaches MUST be extracted from the GPS database. The database approach will therefore have the correct references for distances. It would never be approved for IFR use otherwise.