Positioning in GPS-challenged environments: Dynamic sensor network with distributed GPS aperture and inter-nodal ranging signals

With the increasing demand for sustained navigation in GPS-challenged environment, the concept of multi-sensor integration (GPS augmentation) has been developed and implemented, followed recently by the concept of collaborative navigation, to further improve the navigation capability of a group of users. The objective of the latter is to develop an algorithm, which will provide an optimum navigation solution for all network users for which navigation solution is possible. This paper presents the concept and the algorithmic approach of a new technique for robust GPS positioning in a dynamic sensor network using a distributed GPS aperture and RF ranging signals among the network nodes. The performance assessment, based on simulated data, demonstrates the ability of a networked group of users to operate under adverse conditions, in which an individual user would be impaired. The improvements due to collaborative navigation relative to the individual navigation solutions are demonstrated under various simulated conditions. The collaborative navigation performance was tested using inter-nodal range measurements and GPS as external observations to correct the position error predicted by individual nodes' inertial measurement units (IMUs) of various grades. The experiments verified that collaborative navigation solution significantly improved the results of the individual navigation solution in all cases. Further improvements are expected with the ongoing refinement and optimization of the collaborative navigation algorithms. In addition, primary research challenges are listed and discussed, in order to properly scope the level of research and implementation efforts required to design and implement a real-time collaborative navigation system.