Abstract: The improved vehicle navigation system uses a multiple, orthogonal axes accelerometer, such as two or three accelerometers which are mounted orthogonal to one another. The two axes whose acceleration are to be measured are the longitudinal (nose to rear bumper) axis and lateral (left to right side) axis. The tangential or longitudinal axis acceleration is integrated once to obtain longitudinal speed and is integrated again to produce a vehicle displacement. The lateral accelerometer measures the centripetal force that the vehicle is encountering which is used to compute a centripetal or lateral acceleration. The lateral acceleration is used to obtain a heading change derived from the lateral acceleration information and the longitudinal speed. Using the heading change and the longitudinal acceleration, the improved vehicle navigation system propagates a previous position to a current position. This is accomplished without the need for connection to the vehicle speed sensor and the heading sensor.

Abstract: The improved vehicle navigation system and method uses information from a Global Positioning System (GPS) to obtain velocity vectors, which include speed and heading components, for "dead reckoning" the vehicle position from a previous position. If information from the GPS is not available, then the improved vehicle navigation system uses information from an orthogonal axes accelerometer, such as two or three orthogonally positioned accelerometers, to propagate vehicle position. Because the GPS information should almost always be available, the improved vehicle navigation system relies less on its accelerometers, thereby allowing the use of less expensive accelerometers. The improved vehicle navigation system retains the accuracy of the accelerometers by repeatedly calibrating them with the velocity data obtained from the GPS information. The improved vehicle navigation system calibrates the sensors whenever GPS data is available (for example, once a second at relatively high speeds).