Target geo-location based on laser range finder for airborne electro-optical imaging systems

As the line of sight (LOS) measurement cannot be obtained accurately for a small-scale, airborne, electro-optical imaging system, a laser range finder (LRF) is proposed based on a target geolocation algorithm. According to target locking and tracking characteristics of an airborne photoelectric detection platform, the same target is measured repeatedly. The distance between the airborne electro-optical imaging system and target is measured by the LRF. Considering the ellipsoidal earth model and global digital elevation model, which is defined by the World Geodetic System 1984, a system measurement equation has been established. Owing to the nonlinearity of the measurement equation, an extended Kalman filter is applied to the target geographical position estimation. The geolocation calculation accuracy is primarily affected by the measurement errors of the GPS and LRF and is independent of the LOS measurement error. The influence of the aircraft position measurement and distance measurement errors on the target geolocation calculation accuracy is analyzed using Monte Carlo method. The simulation result demonstrates that the proposed algorithm has high target geolocation accuracy. The validity of the geolocation algorithm is verified by the flight test in which the plane flies at altitude of 8 000 m for photographing the target and the root mean square error of the target geolocation is less than 8 m. When compared with the traditional algorithm, the target geolocation accuracy is improved by four times using our proposed algorithm. Further, this algorithm is easy to deploy and has strong operability and great practical value. © 2019, Science Press. All right reserved.