What information is 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 is the predicted region where the object might be found, determined by how it drifts. To estimate it, you combine the factors that move the object: the total water current, the wind-driven drift of the object (leeway divergence), and a buffer for uncertainties (error). These components are added as vectors because each can push the object in different directions and amounts, and their combined effect defines the path and spread of possible locations. The other options don’t describe how an object moves: wind speed and ceiling influence weather but aren’t used alone to define drift, aircraft speed isn’t about the object’s movement on the water, and temperature or humidity don’t determine the drift path.