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

due to leap seconds (t LSF ), together with the week number (WN LSF ) and the day number (DN) at the end of whichthe leap second becomes effective. Information required to use these parameters to calculate t UTC is in paragraph20.3.3.5.2.4 of IS-GPS-200 except the following definition of t UTC shall be used:t UTC = t LS + A 0-n + A 1-n (t E – t ot + 604800 (WN – WN ot )) + A 2-n (t E – t ot + 604800 (WN – WN ot )) 2 seconds.Table 3.5-3.UTC ParametersParameterNo. ofBits**Scale Factor(LSB)EffectiveRange***UnitsA 0-nA 1-nA 2-nBias coefficient of GPS time scalerelative to UTC time scaleDrift coefficient of GPS time scalerelative to UTC time scaleDrift rate correction coefficient of GPStime scale relative to UTC time scale16* 2 -35 seconds13* 2 -51 sec/sec7* 2 -68 sec/sec 2∆t LS Current or past leap second count 8* 1 secondst ot Time data reference Time of Week 16 2 4 604,784 secondsWN ot Time data reference Week Number 13 1 weeksWN LSF Leap second reference Week Number 13 1 weeksDN Leap second reference Day Number 4**** 1 days∆t LSF Current or future leap second count 8* 1 seconds* Parameters so indicated shall be in two's complement notation;** See Figure 3.5-2 for complete bit allocation;*** Unless otherwise indicated in this column, effective range is the maximum range attainable with indicatedbit allocation and scale factor;**** Right justified.3.5.4.1.2 Ionospheric DataThe ionospheric parameters which allow the “L1 only” user to utilize the ionospheric model for computation of theionospheric delay are contained in subframe 3, page 1. The “one frequency” user should use the model given inparagraph 20.3.3.5.2.5 of IS-GPS-200 to make this correction for the ionospheric effects. The bit lengths, scalefactors, ranges, and units of these parameters are given in Table 20-X of IS-GPS-200.53 IS-GPS-800A8 June 2010