Asset tracking system employing reduced order GPS with compressed GPS satellite identification data

Abstract

Satellite identification data generated when using the Reduced Order GPS (ROGPS) system are compressed, allowing for shorter data transmission times, reduced transmitter energy and reduced satellite channel occupancy. An indexed list of all possible constellations of a subset of all satellites is created. This list is then used at both the tracked object location and the central station to which the satellite identifications must be sent. At the tracked object location, the chosen satellite GPS indices are identified and the list index is found, encoded, and transmitted with only enough bits to uniquely identify it from all other indices in the list. At the central station, the received list index is used to find the satellite constellation corresponding to the chosen satellite GPS indices. The number of bits used to encode the index can be further reduced by reducing the indexed list size. This can be done at both the tracked object and the central station by using a priori knowledge to reduce the possible number of satellites from the full GPS set down to only those that could possibly be visible from the object to be tracked location at a given time.

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