Systems that locate suitably equipped users by means of measurements made by electronic sensors. Typical measurements include distance or bearing from a vehicle to a known point, or direct determination of the present position of the vehicle in a particular coordinate system. From the knowledge of present position, the course and distance to a destination at a known location can be calculated. Most systems are based on the use of electromagnetic (radio) or acoustic waves or inertial sensing. The systems described here are typically used by aircraft, ships, and land and space vehicles. In addition, the use of satellites for land navigation by individuals has become common.