GPS-denied Localization System, 10-R8248
Principal Investigators
Kristopher C. Kozak
Christopher L. Lewis
Marc C. Alban
Samuel E. Slocum
Michael O. Blanton
Inclusive Dates: 09/06/11 – Current
Background — Global Positioning System (GPS) receivers provide a low-cost localization and navigation solution to a wide variety of commercial and military systems. As safety-critical systems come to rely on GPS (and other satellite-based localization systems), concerns have mounted due to its well-known vulnerabilities. GPS has limited accuracy and requires an unobstructed line-of-sight to multiple satellites. Its signals are subject to interference, multi-path, jamming and spoofing. While GPS has become more essential and ubiquitous, few practical alternatives have emerged. The fragility of GPS can be considered one of the limiting factors in the adoption of some cutting-edge technologies such as self-driven automobiles. The objective of this project is to develop a camera-based system that provides real-time localization measurements and can serve as a reliable supplement or alternative to GPS.
Approach — SwRI’s solution to this problem for ground vehicles is to develop two related map-based localization methods that utilize cameras on a vehicle. To this end, SwRI researchers designed a pair of camera systems – a downward-facing camera with high intensity illumination and a forward-facing stereo pair – to address two related aspects of the localization problem. The downward facing camera system allows for extremely high precision localization on pre-driven, mapped routes, while the forward facing camera system allows for localization using both maps generated on pre-driven routes, as well as maps consisting of readily available aerial imagery. By processing the real time imagery acquired with the cameras and comparing the image features/landmarks to the geo-referenced imagery that comprises the map, the location of the cameras (and thus the vehicle on which the cameras are mounted) can be determined. In addition, either camera system can be used to compute differential motion between camera frames, and thus can fill in gaps when the live imagery from the vehicle cannot be confidently matched to the map.
Accomplishments — For the ground-facing camera localization approach, a full hardware system, which includes a camera and synchronized high-intensity illumination, was designed and installed on an SwRI vehicle. An algorithmic framework based on feature matching with geometric constraints was developed as the basis of the localization approach. This approach has been shown in a subsequent analysis to have a very high success rate for positively identifying location (on a variety of road surfaces), with a very low rate of incorrect matches. Finally a simple implementation of a full localization system was implemented on the vehicle, and the ground-facing system was operated successfully in real time on the vehicle. Development of this system is ongoing. For the forward facing stereo camera localization approach, two separate algorithmic frameworks have been developed, a feature matching approach and an image correlation approach. Both methods have been demonstrated to yield successful localization on several types of data, including real projected stereo imagery. Development of this system is also still ongoing.
