The Vectormaster permits rapid solution to problems involving vectors. Such as set/drift adjustments for current, determination of true wind direction and force, and apparent wind to be expected on other headings. Given the position of a storm, and the direction and speed of its advance, you can quickly determine the course which will put maximum distance between your boat and the oncoming storm. A circular slide rule is located on the reverse for the quick solution of time, speed and distance. Instructions included, 7” square.