A passive object will experience the greatest leeway drift, which is of utmost importance to those involved in search and rescue (SAR) operations on inland waterways and open oceans.
Because the search object is located within two dynamic boundary layers with high vertical shear in the velocity profiles of wind and current, Fitzgerald et al. (1993) proposed an operational definition of leeway that helped standardize atmospheric and oceanic reference levels: Leeway is the velocity vector of the SAR object relative to the downwind direction at the search object as it moves relative to the surface current as measured between 0.3m and 1.0m depth caused by winds (adjusted to a reference height of 10m) and waves.
[6] The crosswind component causes the drift object to diverge from straight downwind direction.
[4] Allen and Plourde (1999) listed seventeen studies that used the indirect method of obtaining leeway.
[4] Fitzgerald et al. (1993) were the first to employ the direct method using autonomous outfitted leeway targets off the coast of Newfoundland, which eliminated many of the errors associated with the indirect method and produced a continuous record of leeway for the search object in various oceanic conditions.
Other targets include PIWs, surfboards, sailboats, life capsules, homemade rafts, fishing vessel boating debris and medical/sewage waste.
Modeling leeway divergence is a challenging problem but one that search and rescue agencies are highly interested in.
Statistical models, however, have the ability to resolve leeway in terms of the crosswind and downwind components.
[3] A study conducted by Allen (2005) used constrained and unconstrained linear regression analysis to determine the downwind and crosswind coefficient from the leeway speed and the divergence angles obtained in Allen and Plourde (1999) for all relevant search and rescue leeway objects.
[6] The success of the stochastic trajectory model depends upon the quality and resolution of environmental forcing and precise leeway calculations for the drifting object.