Abstract: A method for determining the drift vector in a watercraft and then graphically projecting an anticipated drift line for a specified target point. The inventive method is preferably carried out by modifying existing GPS plotters. The user initiates a drift vector determination. A memory device receiving positional data then records the starting position of the watercraft and an ending position of the watercraft a suitable amount of time later. The starting and ending points are then used to calculate a drift vector, which includes at least the orientation of the drift and preferably also information abut the speed of the drift. This information is stored in a memory device. A graphical display is used. At some point the user defines a target point, which is shown within the graphical display. The drift vector information is retrieved from memory and a drift line is projected from the target point in a direction which is 180 degrees away from the direction of the drift vector.