GPS World, April 2015
Algorithms Methods INNOVATION This new model can be extended to the triple frequency case very easily as it does not involve explicit dual frequency combinations 5 This new model simpli es the concept of phase biases for ambiguity resolution This representation is very attractive because no assumption is made on the method used to identify phase biases on the network side All the implementations are valid if they respect this proposed model It also allows convenient interoperability if the network and user sides implement different ambiguity resolution methods TABLE 1 summarizes the different messages used for PPP AR in the context of RTCM SSR Parameter Nature RTCM SSR message Quantity GPS GLONASS orbits clocks 1060 1066 D h p GPS code biases 1059 1065 b P GPS phase biases 1265 b L TABLE 1 RTCM SSR messages for PPP AR Bias Estimation in the Dual Frequency Case The new phase biases identi cation in the dual frequency case is straightforward There are two biases to be estimated using two combinations μ and h The problem to be solved is described in FIGURE 1 It can be solved very easily on the network side by means of a 2 2 matrix inversion 6 with 0 200 400 600 800 1000 1200 1400 1600 1800 Time seconds 0 200 400 600 800 1000 1200 1400 1600 1800 50 45 40 35 30 25 20 15 10 05 00 60 50 40 30 20 10 00 Time seconds Ambiguity cycles Ambiguity cycles FIGURE 4 Ambiguity residuals for widelane combinations top 1 2 widelane bottom 1 5 widelane www gpsworld com April 2015 GPS World 45
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