Safety, Fire & Survival · SAR — Datum and Drift
In SAR planning, why must the search 'datum' be updated over time?
- ATo account for magnetic variation only
- BBecause the Earth's rotation moves the casualty east
- CDatum never changes once set
- DWind and current cause the survivors/craft to drift, so the most probable position moves and the search area must shift accordingly✓ Correct
Explanation
Datum is the best estimate of the search object's position. Leeway (wind on the object) and current set carry survivors and craft away from the incident point, so datum is advanced for elapsed drift; otherwise searchers comb water the casualty has already left.
Authority: IAMSAR Manual; leeway and drift
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