Fusion of Reference-Aided GPS, Imagery, and Inertial Information for Airborne Geolocation

摘要

A remote sensor suite is described that utilizes kinematicrnand differential GPS, a digital camera, and a tacticalgradernInertial Navigation System (INS). The camera andrnINS are fixed to a scan platform housed in a turret. Thernturret is attached to the chin of a light, single-enginernaircraft. Real-time differential GPS positioning alongrnwith the real-time INS observations provide a pointingrnvector to a specific location on the ground, allowing therncamera to continuously stare at that location as the aircraftrnflies by. Post-mission integration of the camera positionrnand attitude, along with image information, can providernthe ground locations of any point in the image in WorldrnGeodetic System (WGS-84) coordinates.rnAccurate geolocation of ground targets was demonstratedrnusing data collected during a test conducted near Duck,rnNorth Carolina in October and November 1999. GPSrnpseudorange and phase measurements, as well as datarnfrom an inertial measurement unit (IMU), were collectedrnin real-time; however, processing was done after the test.rnAbsolute positions from the aircraft were obtained fromrneither short- or long-baseline kinematic reference-aidedrnGPS. Short-baseline kinematic GPS provided aircraftrnpositions with centimeter-level accuracy, while multiplereference,rnlong- baseline, kinematic GPS (greater thanrn1000 km) provided decimeter-level accuracy. The use ofrnthese positions permitted more accurate IMU/camerarnattitude estimation than that achievable using standardrndifferential GPS techniques. In particular, sub-milliradianrnstandard errors for camera pointing accuracy wererndemonstrated. Target geolocation was performed using arntwo-image triangulation method. Meter-level target