Abstract: A method of determining the position of a tape in a tape cartridge having a first hub, a second hub, a means for measuring the rotation of the first hub, a means for measuring the rotation of the second hub, and a length of tape with one end of the tape wrapped around the first hub and the other tape end wrapped around the second hub, the tape having a relatively uniform and predetermined thickness and the hubs having predetermined diameters. In accordance with the method, the first hub is locked to prevent rotation of the first hub. A length of tape is then extracted from the cartridge, which causes the second hub to rotate as tape is unwound from the second hub. There is then determined the angle rotated by the second hub in response to the length of tape being unwound from the second hub. The first hub is unlocked and the second hub is locked.