DGPS positioning using carrier phase for precision navigation

DGPS with carrier smoothed code is employed widely in real time applications. Its accuracy level can satisfy the ICAO-CAT-I and CAT-II landing requirements according to the authors experiences. The investigation in the paper shows potential possibility and conditions to use this technique for the accuracy requirement of CAT-III. For accuracy improvement, DGPS with only carrier phase measurement is needed. However, in navigation integer ambiguities of carrier phase measurement must be resolved during flight. The paper presents a triple difference technique for six unknowns, The phase ambiguities, instead of being resolved, are eliminated by triple differencing, The six coordinates of the mobile receiver at two epochs are the unknowns to be determinated in real time. The combined GPS/GLONASS system will ultimately provide a simultaneous availability to receive eight or more satellites. With seven or more observable satellites one can get an analytical resolution of position without static initialization or any searching technique for ambiguities. It is also possible to achieve an analytical solution with GPS alone by using two reference stations. From each reference/mobile station combination at least three triple difference equations can be obtained so that six independent equations together are sufficient to also resolve six unknowns. The initial results of this technique are presented