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

3.5.3.8 SV Clock Accuracy EstimatesBits 460 through 470 of subframe 2 shall contain the URA oc Index, URA oc1 Index, and URA oc2 Index of the SV(reference paragraph 6.2.1) for the user. The URA oc Index together with URA oc1 Index and URA oc2 Index shall givethe clock-related user range accuracy of the SV as a function of time since the prediction (t op ) used to generate theuploaded clock correction polynomial terms.Clock-related URA (URAoc) accounts for signal-in-space contributions to user range error that include, but are notlimited to, the following: the net effect of clock parameter and code phase error in the transmitted signal for singlefrequencyusers who correct the code phase as described in Section 3.5.3.9.1, as well as the net effect of clockparameter, code phase, and intersignal correction error for dual-frequency L1/L2 and L1/L5 users who correct forgroup delay and ionospheric effects as described in Section 3.5.3.9.2 and Section 3.5.3.9.3.The user shall calculate the clock-related URA with the equation (in meters):URA oc = URA ocb + URA oc1 (t – t op )URA oc = URA ocb + URA oc1 (t – t op ) + URA oc2 (t – t op – 93,600) 2for t-t op < 93,600 secondsfor t-t op > 93,600 secondswheret = GPS time (must account for beginning or end of week crossovers),t op = time of week of the state estimate utilized for the prediction of satellite clock correction parameters.The CS shall derive URA ocb at time t op which, when used together with URA oc1 and URA oc2 in the above equations,results in the minimum URA oc that is greater than the predicted URA oc during the entire duration up to 14 daysafter t op .47 IS-GPS-800A8 June 2010