The International Measurement System (IMS) uses a computerized velocity prediction program (VPP) to calculate the performance of a measured hull and rig in winds from six to twenty knots, at any sailing angle. A regatta is scored by comparing a yacht's performance with predictions of the VPP. The winner is the yacht whose performance, relative to its VPP predictions, is the best, compared to all other yachts in its class or division.
This paper discusses different methods of malcing the comparison and accounting for various factors in the race such as wind shifts and current on the course. Decisions made by race managers and/or developers of scoring programs can significantly impact results. Illustrative examples show the effects that these decisions can have.
In 1994 the number of data points available for use in scoring yachts in custom courses doubled. Alternative ways of using these data are illustrated by application to a sample regatta.