Direct geo-referencing technique for rapid positioning of targets and environmental products using tactical grade airborne imaging data

Small airborne electro-optical imaging systems are being used by U.S. armed forces for rapidly identifying elusive targets, and systems that are effective in this context also could be useful for retrieving a number of oceanographic products. Whereas accurate geodetic positioning of militarily important targets is critical for a number of military missions, accurate positioning of retrieved environmental products such as topography and bathymetry is important for both military missions and non-military applications. However, a common problem with tactical-grade systems is lack of good positioning and viewing attitude of the camera, leading to inaccurate geo-location of retrieved products. This paper describes an approach that has shown considerable promise in solving this geo-location problem by using inexpensive and commonly available components in combination with a data processing algorithm specifically developed for this purpose. The raw inertial data for the camera pointing angles are corrected by using observable features in the images. The method has been demonstrated to reduce attitude errors by more than an order of magnitude to <1 milliradian, which is exceptional performance for a tactical-grade inertial navigation system, thereby providing accurate geo-locations of targets. This is sufficient to meet the geo-positioning requirements for all the above-mentioned products, thereby enabling the use of tactical UAVs with rather inexpensive sensor components for these missions.