Determination of Acceptable Error for Leeway Rate Estimates of Untested Search Objects

The leeway of an object directly impacts drift predictions and search and rescue operations. The standard method for calculating the leeway of an object is through direct measurement of environmental forces. However, direct measurement is costly and requires extensive field testing. As a result, many objects do not have accurate leeway values. If a case arises involving an object with unknown leeway, its drift must be estimated based on known objects of similar shape and size. Uncertainty in leeway, especially when using a proxy object, may result in applying the incorrect amount of wind forcing and can lead to differences in the predicted location of objects of interest. This study conducted a sensitivity analysis on the impact of leeway rate on drift prediction size and location. Four hundred drift simulations were conducted under matrixed wind, current, and leeway values to determine the acceptable margin of error for leeway rate. Acceptable error was defined as any difference in leeway rate that resulted in at least 50% overlap between the particle distribution of the true object and the proxy over a 36 h drift. Results from the sensitivity analysis, and testing with real environmental data, indicate that leeway rate can have an error ±1% of the wind speed.