Power matching approach for GPS coverage extension

The inherent problem of the Global Positioning System (GPS), which is signal obstruction, remains the major obstacle that inhibits it from functioning as a "reliable stand-alone" positioning system. Therefore, it is becoming a common practice to couple the GPS system with an external positioning system whenever the GPS receiver is expected to operate in regions of dense canopy, such as urban areas. Commercial automobile navigation systems currently employ a GPS receiver coupled with a dead reckoning (DR) system and a map-matching algorithm. Most DR systems, which compensate for GPS inaccuracies and frequent GPS signal obstructions, employ an odometer and a directional sensor. In this paper, a power matching approach is proposed for GPS coverage extension in urban area. The algorithm, based on a statistical measure, correlates the received power from different GPS satellite vehicles (SVs), which leads to a specific signature, i.e., to a topographical database with periodic time-varying estimates of the received powers of SVs. An experimental approach is presented to examine the feasibility of applying the proposed positioning system.