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

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3.5.3 Subframe 2Subframe 2 provides users with the requisite data to correct SV time and to calculate SV position. Nominally, thesubframe 2 data is invariant for the nominal transmission interval of two hours. The contents of the SV ephemerisrepresentation, clock correction, and accuracy parameters are defined below, followed by material pertinent to theuse of the data.The general format of ephemeris data of subframe 2 consists of data fields for reference time tags, a set ofgravitational harmonic correction terms, rates and rate corrections to quasi-Keplerian elements, and an accuracyindicator for ephemeris-related data.The ephemeris parameters describe the orbit of the transmitting SV during the curve fit interval of three hours. Thenominal transmission interval is two hours, and shall coincide with the first two hours of the curve fit interval. Theperiod of applicability for ephemeris data coincides with the entire three-hour curve fit interval. Table 3.5-1 givesthe definition of the orbital parameters using terminology typical of Keplerian orbital parameters; it is noted,however, that the transmitted parameter values are expressed such that they provide the best trajectory fit in Earth-Centered, Earth-Fixed (ECEF) coordinates for each specific fit interval. The user shall not interpret intermediatecoordinate values as pertaining to any conventional coordinate system.Any change in the subframe 2 ephemeris and clock data shall be accomplished with a simultaneous change in the t oevalue. The SV shall assure that the t oe value, for at least the first data set transmitted by an SV after an upload, isdifferent from that transmitted prior to the cutover. The eight LSBs of t oe for each data set shall be different fromthe eight LSBs of t oe transmitted during the previous six hours by the SV.The general format of clock data in subframe 2 consists of data fields for SV clock correction coefficients. Theclock parameters of subframe 2 describe the SV time scale during the period of validity. The parameters areapplicable during the time in which they are transmitted. Beyond that time, they are still applicable, however, themost recent data set should be used since the accuracy degrades over time.38 IS-GPS-800A8 June 2010
Table 3.5-1. Subframe 2 Parameters (1 of 3)WNParameterWeek No.No. ofBits**13ScaleFactor(LSB)1EffectiveRange***weeksUnitsITOWt opL1C healthURA oe Indext oe∆A ****A∆n 0∆n 0M 0-ne n nInterval time of weekData predict time of weekSV ephemeris accuracy indexEphemeris/clock datareference time of weekSemi-major axis difference atreference timeChange rate in semi-majoraxisMean Motion difference fromcomputed value at referencetimeRate of mean motiondifference from computedvalueMean anomaly at referencetimeEccentricityArgument of perigee81115*1126*25*17*23*33*3333*83300 604,500300 604,5002 -92 -212 -442 -572 -322 -342 -32(see text)seconds(see text)(see text)secondsmetersmeters/secsemi-circles/secsemi-circles/sec 2semi-circlesdimensionlesssemi-circles* Parameters so indicated are in two’s complement notation;** See Figure 3.5-1 for complete bit allocation in Subframe 2;*** Unless otherwise indicated in this column, effective range is the maximum range attainable withindicated bit allocation and scale factor.**** Relative to A REF = 26,559,710 meters.39 IS-GPS-800A8 June 2010
Page 1 and 2: IS-GPS-800A8 June 2010GLOBAL POSITI
Page 3 and 4: REVISION RECORDLTR DESCRIPTION DATE
Page 5 and 6: 3.2.3.3 Cyclic Redundancy Check ...
Page 7 and 8: LIST OF FIGURESFigure 3.2-1. Genera
Page 9 and 10: 1. INTRODUCTION1.1 ScopeThis Interf
Page 11 and 12: 3. SIGNAL REQUIREMENTSThe requireme
Page 13 and 14: Carriers of the two L1C components
Page 15 and 16: 3.2.2 PRN Code CharacteristicsThe c
Page 17 and 18: The overlay codes are derived from
Page 19 and 20: 3.2-2 L1C Ranging Codes Parameter A
Page 21 and 22: GPS PRNSignal No.3.2-3 L1C O Overla
Page 23 and 24: FIXED LENGTH-10223 LEGENDRE SEQUENC
Page 25 and 26: 3.2.2.2 Non-Standard CodesThe non-s
Page 27 and 28: corresponding to MSB = 0. (A SV tra
Page 29 and 30: This code has the following charact
Page 31 and 32: 3.2.3.5 InterleavingThe 1748 encode
Page 33 and 34: 3.3 Signal ModulationThe signals mo
Page 35 and 36: Bit valueL1C DbitstreamSubcarrier s
Page 37 and 38: 3.5 Message DefinitionAs shown in F
Page 40 and 41: DIRECTION OF DATA FLOW FROM SV100 B
Page 48 and 49: Table 3.5-1. Subframe 2 Parameters
Page 50 and 51: 3.5.3.1 Transmission Week NumberBit
Page 52 and 53: 3.5.3.6 Ephemeris Parameter Charact
Page 54 and 55: Table 3.5-2. Elements of Coordinate
Page 56 and 57: The user shall use the broadcast UR
Page 58 and 59: where, ISC L1CD is provided to the
Page 60 and 61: 3.5.3.10.1 Integrity Status Flag (I
Page 62 and 63: The ionospheric data shall be updat
Page 64 and 65: 3.5.4.2.3 User Algorithm for Applic
Page 66 and 67: transmitted by the SVs will degrade
Page 68 and 69: Table 3.5-7.Midi Almanac Parameters
Page 70 and 71: MSBCDC = Clock Differential Correct
Page 72 and 73: 3.5.4.5 Subframe 3, Page 6 - TextSu
Page 74 and 75: 5. RESERVED66 IS-GPS-800A8 June 201
Page 76 and 77: LSF - Leap Seconds FutureL1C - Comm
Page 78 and 79: Table 6.2-1.Legendre Sequence (Octa
Page 80 and 81: Table 6.2-2 LDPC Submatrix A for Su
Page 90 and 91: Table 6.2-3. LDPC Submatrix B for S
Page 92 and 93: Table 6.2-7. LDPC Submatrix T for s
Page 94 and 95: Table 6.2-7. LDPC Submatrix T for s
Page 96 and 97:
Table 6.2-8. LDPC Submatrix A for s
Page 98 and 99:
Table 6.2-8. LDPC Submatrix A for s
Page 100 and 101:
Table 6.2-9. LDPC Submatrix B for S
Page 102 and 103:
Table 6.2-13. LDPC Submatrix T for
Page 104 and 105:
Table 6.2-16. Number of 1’s in LD
Page 106 and 107:
6.3 Supporting Material6.3.1 Additi
Page 108 and 109:
Table 6.3-1 Additional L1C Ranging
Page 110 and 111:
Page 112 and 113:
Page 114 and 115:
PRNSignalNo.Table 6.3-2. Additional
Page 116 and 117:
PRNSignalNo.Table 6.3-2 Additional
Page 118 and 119:
Page 120 and 121:
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IS-GPS-800A - US Coast Guard Navigation Center

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