IS-GPS-800A - US Coast Guard Navigation Center

The transmitted URA oc1 Index is an integer value in the range 0 to 7. URA oc1 Index has the following relationship tothe URA oc1 :whereURA oc1 =1N (meters/second)2N = 4 + URA oc1 Index.The transmitted URA oc2 Index is an integer value in the range 0 to 7. URA oc2 Index has the following relationship tothe URA oc2 :whereURA oc2 =1N (meters/second 2 )2N = 25 + URA oc2 Index.3.5.3.9 Group Delay Correction ParametersBits 527 through 565 of subframe 2 provide the group delay differential correction terms for L1C signal users. Thefollowing algorithms shall apply when interpreting the correction parameters in the message. The bit lengths, scalefactors, ranges, and units of these parameters are given in Table 3.5-1. The bit string of “1000000000000” shallindicate that the group delay value is not available. The related algorithm is given in paragraphs 3.5.3.9.1 and3.5.3.9.2.3.5.3.9.1 Inter-Signal CorrectionThe correction terms, T GD , ISC L1CP , and ISC L1CD , are initially provided by the CS to account for the effect of SVinter-signal biases between L1 P(Y) and L2 P(Y), between L1 P(Y) and L1C P , and between L1 P(Y) and L1C D ,respectively, based on measurements made by the SV contractor during SV manufacture. The values of T GD andISCs for each SV may be subsequently updated to reflect the actual on-orbit group delay differential. For maximumaccuracy, the single frequency L1C P user must use the correction terms to make further modifications to the codephase offset in paragraph 20.3.3.3.3.1 of IS-GPS-200 with the equation:(t SV ) L1CP = t SV - T GD + ISC L1CPwhere T GD (see paragraph 20.3.3.3.3.2 of IS-GPS-200) and ISC L1CP are provided to the user as subframe 2 data. Formaximum accuracy, the single frequency L1C D user must use the correction terms to make further modifications tothe code phase offset given by:(t SV ) L1CD = t SV - T GD + ISC L1CD49 IS-GPS-800A8 June 2010