What is a Datum? What are the factors to be considered for establishing the datum?

Datum is the geographical reference for the area to be searched.

The following factors should be considered:

  • Reported position and time of the SAR incident
  • Any supplementary information such as DF bearings or sightings
  • Time interval between the incident and the arrival of SAR facilities
  • Estimated surface movements of the distressed craft or survival craft, depending on drift
  • Drift distance is drift speed multiplied by the time interval between the incident time, or time of the last computed datum, and the commence search time
  • Datum position is found by moving from the incident position, or last computed datum position, the drift distance in the drift direction and plotting the resulting position on a suitable chart.