Low cost underlay to GPS for a metropolitan area geographic positioning system

Concerns still remain about the continued availability of the GPS system for use as the sole means of navigation in many applications due to the single military ownership of the system. The problems arise in use of the GPS basically when the integrity and quality of GPS signals are in doubt, or when the signals are not available for use. Some of the solutions put forward in this direction, therefore, are to monitor the integrity and quality of the GPS signals, and provide a ranging capability using additional GPS like satellites as reference so that a critical operation is given a timely warning and is not suddenly affected due to malfunctioning or otherwise in the GPS. This is achieved using a satellite based system which works primarily as an underlay to the global positioning satellite system, and is complementary to it in its function. Such a system is meant to be used for a very large area coverage under the foot prints of the satellite. It would, however, be an overkill if the area of operation is small, such as a metropolitan area. This paper suggests a low cost approach to serve as an underlay to the GPS for a small area coverage. The system proposes to use Kytoons (tethered balloons), the geometry of which is shown