Which components are required to calculate a datum area?

• A. Vector sum of total water current, leeway divergence, and error
• B. Wind speed and ceiling
• C. Aircraft speed
• D. Temperature and humidity

Answer: (A)

Datum area in SAR planning comes from modeling how the object will move and how uncertain that movement is over the search interval. The best way to estimate that area is to combine the mean drift motion with the spread around it: you take the vector sum of the total water current (the baseline movement caused by how the water itself carries the object), add leeway divergence (how wind-driven drift causes the object to spread from the mean path), and include an error term to capture uncertainties in currents, leeway estimates, timing, and other factors. This trio—mean drift from currents, additional spread from leeway, and error—defines the probable location area, i.e., the datum area.

Wind speed and ceiling, aircraft speed, or temperature and humidity don’t directly build that drift-based area. They influence planning in other ways, but they don’t provide the essential combination of mean drift plus its uncertainty needed to define the datum area.