Automated geolocation network for use in GPS-degraded environments

Geolocation in instances where the Global Positioning System (GPS) is degraded has become an important issue in today´s world. Many military and commercial applications, including unmanned systems, require an accurate location on the earth to be determined, even inside buildings or complex urban environments. This paper presents a method of complementing GPS with a mobile ad-hoc network of nodes, each of which are capable of obtaining ranges to surrounding nodes. GPS is used where available, but this method takes over when GPS is degraded. In this approach, all nodes can potentially be used by surrounding nodes to calculate position. Algorithms are being developed to select the best nodes from those available and to perform the location calculation. Some important issues are addressed, including determining the number of nodes needed to perform accurate calculations given certain error situations and understanding the way error propagates between nodes.