An Alternate Approach to GPS Denied Navigation Based on Monocular SLAM Techniques

Greg Farley and Mark Chapman

Abstract:	GPS denied navigation indoors, underground, on moving reference frames, and in urban canyons can be achieved in a practical approach suitable for use by the war fighter or emergency responder. Rockwell Collins is working to successfully advance the state of the art in robotic vision algorithms and coupled MEMS based dead reckoning modules to demonstrate accurate long term navigation in GPS denied environments. Significant efforts continue across the navigation industry to improve methods of correcting MEMS based dead reckoning modules to allow short term GPS denied navigation accuracy. The general approach of correcting or aiding the MEMS to create a navigation solution is hampered by several practical issues: Magnetic anomalies induce significant error conditions and distortions that cannot be predicted without a priori knowledge of the environment to be traversed. Angular rotation error propagates creating a linearly increasing navigation error. Correction of the heading errors requires extremely precise aiding in order to achieve practical navigation accuracy for more than a few minutes. Body stride estimation routines fail to accurately compensate for changing body postures and stride lengths that result from combat operations and intricate search and rescue activities. Rockwell Collins has addressed these issues by challenging the fundamental assumption that MEMS aiding will provide an acceptable solution. Instead, robotic vision algorithm based navigation is aided by the MEMS. Current robotic vision algorithms such as Simultaneous Location and Mapping (SLAM) are throughput intensive and are not practical for the dismounted user. The use of the MEMS provides excellent instantaneous sensor pointing information that reduces the SLAM processing requirements significantly. The use of Feature Constellation Tracking (FCT) algorithm improvements further reduce the processing requirements by allowing intelligent thinning of the features tracked. This paper will summarize the results of recent testing of a GPS denied brass board. The brass board was developed utilizing a single camera and inverse depth parameterization to allow accurate passive ranging to local landmarks. FCT software dynamically tracks up to 64 features aided by a MEMS module. Monocular SLAM routines are used to compute real time navigation solutions. The test bed was evaluated both indoors and outdoors against known truth courses and provides startling results.
Published in:	Proceedings of the 2008 National Technical Meeting of The Institute of Navigation January 28 - 30, 2008 The Catamaran Resort Hotel San Diego, CA
Pages:	810 - 818
Cite this article:	Farley, Greg, Chapman, Mark, "An Alternate Approach to GPS Denied Navigation Based on Monocular SLAM Techniques," Proceedings of the 2008 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2008, pp. 810-818.
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