Mobile tracking units employing motion sensors for reducing power consumption therein

A mobile tracking unit for a vehicle location system, comprising:

• a navigation set for generating data substantially corresponding to a respective vehicle position, said navigation set being adapted to be periodically energized at a selected activation rate F.sub.G while the vehicle is moving to generate vehicle position data;
• an electromagnetic emitter adapted to be periodically energized at a selected activation rate F.sub.EM while the vehicle is moving, for transmitting at least the vehicle position data;
• a motion sensor for generating data indicative of vehicle motion;
• and
• a tracking unit controller coupled to said motion sensor to receive the vehicle motion data, said tracking unit controller being adapted to control said navigation set and said emitter based upon the vehicle motion data so that during times when the vehicle is substantially stationary each of said activation rates F.sub.G and F.sub.EM can be respectively decreased by a predetermined factor, thereby reducing overall power consumption of said tracking unit, said tracking unit controller being further adapted to revert to activation rates F.sub.G and F.sub.EM when said motion sensor indicates renewed vehicle motion, thereby avoiding substantial loss of vehicle position data during renewed vehicle motion.

A method of operating a mobile tracking unit for a vehicle location system, said method comprising:

• providing a navigation set capable of generating data substantially indicative of a respective vehicle position;
• periodically energizing said navigation set at a selected activation rate F.sub.G while the vehicle is moving to generate vehicle position data;
• generating data indicative of vehicle motion;
• controlling said navigation set in accordance with the vehicle motion data so that when the vehicle is substantially stationary the activation rate F.sub.G can be respectively decreased by a predetermined factor, thereby reducing overall power consumption of said tracking unit;
• and
• controlling said navigation set in accordance with the vehicle motion data to revert to activation rate F.sub.G when the motion sensor indicates renewed vehicle motion, thereby avoiding substantial loss of vehicle position data during times of renewed vehicle motion.