GPS World, March 2016

2 1 0 1 15 10 5 0 5 10 15 20 0 1 2 3 DC FIGURE 4 Transformed FCB and IRC products to code phase relative clock correction on day of year 28 of 2015 for PRN 10 DC was included for comparison Linear trend has been removed MARCH 2016 WWW GPSWORLD COM GPS WORLD 53 FCB The FCB products consist of and which are estimated in the network solution using International GNSS Service IGS ultra rapid orbit and clock products The fundamental difference between the FCB and DC products is that is not determined in the DC method but assimilated within the clock estimates Also is assumed constant over a 48 hour time period whereas in the DC method the is neither constrained nor smoothed Here is the transformation matrix used to transform from FCB to the DC model 3 where z 1 is the single differenced L1 ambiguity and z w is the single differenced widelane ambiguity IRC The original IRC products used a decoupledlike approach where independent clocks and were transmitted for the pseudorange and carrier phase measurements and widelane satellite hardware delays were estimated A redefined model was presented in 2014 where a state space approach was adopted such that one phase bias per phase observable and was identified and broadcast The primary benefit of such an approach is interoperability allowing the network and user side to implement different ambiguity resolution methods Here is the transformation matrix used to transform from IRC to the DC model 4 where d 12 represents Analysis of Transformed Products In FIGURES 3 to 5 we present the FCB and IRC products transformed to the DC format The presented format was selected because it represents the nature of the transmitted real time DC products The philosophy of the DC model refers to the satellite hardware delay as an unmodeled timing error and as such the satellite carrier phase clocks in Figure 3 are in units of seconds and in Figures 4 and 5 are in units of nanoseconds Nanoseconds were selected because of the magnitude of the relative satellite pseudorange and widelane clock error as well as being more bandwidth efficient Figure 3 illustrates the FCB and IRC products transformed FCB Code clock Wideland Narrowlane IRC Code clock Phase bias Code bias DC Phase clock Relative code clock Relative widelane clock 10 4 0 5 10 15 20 16065 16070 16075 16080 16085 16090 16095 FCB DC IRC Time hours Satellite carrier phase clock error seconds 0 5 10 15 20 2 FCB 0 5 10 15 20 0 Satellite relative clock error nanoseconds Time hours 4 IRC FIGURE 2 Transformation of FCB and IRC products to DC input format FIGURE 3 Transformed FCB and IRC satellite carrier phase clock correction on day of year 28 of 2015 for PRN 10 DC was included for comparison