Civilian GPS: The Benefits of Three Frequencies

A third civil frequency at 1176.45 Mhz. will be added to the GPS system. This new frequency will bring a number of benefits. The aviation user will be one of the prime beneficiaries because the new frequency is in a protected aviation band. Thus, the system will be more robust against interference and jamming. The carrier-phase differential user will also be a prime beneficiary as long as his application has a reasonably short baseline. It is this high accuracy use which is explored in some depth. The process of forming linear combinations of both the code and carrier-phase measurements is studied and the benefits and problems explained.