INS Aiding by Tracking an Unknown Ground Object

The reduction of the navigation error in an inertial navigation system by optically tracking a ground object is investigated. Multiple observations of the ground object are used. The location of the ground object is assumed unknown. A careful analysis of the measurement situation at hand reveals that by optically tracking an unknown ground object using passive, bearings-only measurements, the aircraft's angle of attack and sideslip angle can be measured. Thus, two new independent measurement equations featuring the aircraft's angular navigation variables are obtained. Hence, by optically tracking over time an unknown ground object, inertial navigation system aiding is in fact possible. Moreover, the estimation algorithm, which operates on the bearing measurements record, simultaneously, and in parallel, produces corrections required for both inertial navigation system aiding and geo-location of the ground object. The theory presented in this paper is sufficiently general to encompass the conventional methods of inertial navigation system updating where both bearing and range measurements are used and the coordinates of the ground object are known. In all cases where additional independent measurements and/or prior information are used, the accuracy of both the navigation solution and the geo- location are enhanced.Air Force Inst of Tech Wright-Patterson AFB OH School of Engineering and Management is the author of 'INS Aiding by Tracking an Unknown Ground Object', published 2002 under ISBN 9781423511397 and ISBN 1423511395.