Patent ID: 6185502
Filing Date: 2001-02-06
Classification: G01C

Abstract:
A passive position fix system on a vehicle, the vehicle having a geographic position over the earth, comprising:(a) gyro means for providing a first gyro position of the vehicle;(b) map storage means for receiving the first gyro position and in response providing map-sets associated with geographic positions in the vicinity of the first gyro position provided by the gyro means, each map-set comprising a stored set of gravity gradients and a gravity anomaly at an associated geographic position on the earth;(c) gravity sensor means for providing a GSS-set, the GSS-set comprising a sensed set of gravity gradients values and a gravity anomaly value at the geographic position of the vehicle;(d) comparator means for receiving the GSS-set and for sequencially receiving the map-sets and for determining when there is a match between the GSS-set and a map-set and for providing a displacement vector based on which map-set matches the GSS-set; and(e) processor means for placing a second gyro position in the gyro means based on the first gyro position and on the displacement vector.