Collaborative localization enhancement to the Global Positioning System

The Global Positioning System (GPS) is the dominant position location system in operation. It uses 31 operational satellites producing eight line of sight satellites available to users at all times. However if a user´s visibility is blocked from large buildings, mountains, or the user is located indoors, the number of visible satellites decreases degrading accuracy and availability. Additionally, the signal quality is also degraded in such environments. This paper therefore explores the effect of collaborating users with known (or estimated) distances between the users. Specifically, we examine the usefulness of multiple GPS receivers using measured inter-receiver distances along with standard pseudoranges to cooperatively determine all receiver locations.