This paper investigates how to take advantage of the known position of a point at which a single frequency GPS receiver is located. Using this reference point and a single frequency receiver, a precise relative positioning method is developed. This method is particularly suited for the applications whose accuracy requirements are relaxed as time passes. In some circumstances, one requires a far better accuracy than a single frequency receiver using standalone GPS or WAAS provides. Further, typical precise positioning methods such as differential GPS (DGPS), real time kinematic survey (RTK), and precise point positioning (PPP) cannot be used due to hardware or cost limitations. This difficult situation can be overcome with the new algorithm, precise relative positioning (PRP), described in this paper. The PRP method requires raw measurements (e.g. pseudo ranges, carrier phase measurements, and ephemeris) from a single frequency receiver. It also requires a reference point. The reference point can be an initial position of a receiver (or any position during navigation for post-processing) that can be obtained by using various techniques, for example, the use of other sensors. The PRP has two modes. One is Iono-Free (I-F) PRP, the other one is Carrier-Based (C-B) PRP. The I-F PRP significantly mitigates the effect of multipath and ionosphere delays and cancels out user receiver clock errors by using combinations of pseudoranges and carrier phase measurements between satellites. On the other hand, C-B PRP uses only carrier phase measurement as ranging sources. Therefore, the I-F PRP can achieve better stability than standalone GPS or WAAS can provide, and the C-B PRP provides precise position solutions in a short-time application. The PRP is particularly well suited to the problems of accurate aircraft position determinations such as flight inspections. Preliminary results show a centimeter to decimeter level of stability in horizontal and vertical planes.
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