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

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3.5.3.1 Transmission Week NumberBits 1 through 13 of subframe 2 shall contain 13 bits that are a modulo-8192 binary representation of the currentGPS week number at the start of the data set transmission interval (see paragraph 6.2.2).3.5.3.2 ITOWBits 14 through 21 of subframe 2 shall contain 8 bits representing ITOW count defined as being equal to the numberof two-hour epochs that have occurred since the transition from the previous week. The count is short-cycled suchthat the range of the ITOW-count is from 0 to 83 2-hour epochs (equaling one week) and is reset to zero at the endof each week. The ITOW-count's zero state is defined as that 2-hour epoch which is coincident with the start of thepresent week. This epoch occurs at (approximately) midnight Saturday night-Sunday morning, where midnight isdefined as 0000 hours on the UTC scale that is nominally referenced to the Greenwich Meridian. The occurrence ofthe “zero state epoch” may differ by a few seconds from 0000 hours on the UTC scale since UTC is periodicallycorrected with leap seconds while GPS time is continuous without such correction.3.5.3.3 Data Predict Time of WeekBits 22 through 32 of subframe 2 shall contain the data predict time of week (t op ). The t op term provides the epochtime of week of the state estimate utilized for the prediction of satellite quasi-Keplerian ephemeris parameters.3.5.3.4 L1C Signal HealthThe one-bit health indication in bit 33 of subframe 2 refers to the L1C signal of the transmitting SV. The health ofthe signal is indicated by:0 = Signal OK,1 = Signal bad or unavailable.The predicted health data will be updated at the time of upload when a new data set has been built by the CS. Thetransmitted health data may not correspond to the actual health of the transmitting SV. In real time, if the L1Csignal becomes unhealthy, the status change will normally be indicated by the broadcast of non-standard code or beindicated by the health bits as described in subframe 2.Additional SV health data are given in the almanac in subframe 3, pages 3 and 4. The data given in subframe 2 maydiffer from that shown in other messages of the transmitting SV and/or other SVs since the latter may be updated ata different time. Subframe 2 data is the most reliable; subframe 3 data is intended only to aid acquisition.3.5.3.5 SV AccuracyBits 34 through 38 of subframe 2 shall contain the ephemeris User Range Accuracy (URA oe ) index of the SV.URA oe index shall provide the ephemeris-related user range accuracy index of the SV as a function of the current42 IS-GPS-800A8 June 2010
ephemeris message curve fit interval. While the ephemeris-related URA may vary over the ephemeris messagecurve fit interval, the URA oe index (N) in subframe 2 shall correspond to the maximum URA oe expected over theentire curve fit interval.The URA oe index is a two’s complement representation of a signed integer in the range of +15 to –16 and has thefollowing relationship to the ephemeris URA:URA oe IndexURA oe (meters)15 6144.00 < URA oe14 3072.00 < URA oe 6144.0013 1536.00 < URA oe 3072.0012 768.00 < URA oe 1536.0011 384.00 < URA oe 768.0010 192.00 < URA oe 384.009 96.00 < URA oe 192.008 48.00 < URA oe 96.007 24.00 < URA oe 48.006 13.65 < URA oe 24.005 9.65 < URA oe 13.654 6.85 < URA oe 9.653 4.85 < URA oe 6.852 3.40 < URA oe 4.851 2.40 < URA oe 3.400 1.70 < URA oe 2.40-1 1.20 < URA oe 1.70-2 0.85 < URA oe 1.20-3 0.60 < URA oe 0.85-4 0.43 < URA oe 0.60-5 0.30 < URA oe 0.43-6 0.21 < URA oe 0.30-7 0.15 < URA oe 0.21-8 0.11 < URA oe 0.15-9 0.08 < URA oe 0.11-10 0.06 < URA oe 0.08-11 0.04 < URA oe 0.06-12 0.03 < URA oe 0.04-13 0.02 < URA oe 0.03-14 0.01 < URA oe 0.02-15 URA oe 0.01-16 No accuracy prediction available—use at own risk43 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 46 and 47: 3.5.3 Subframe 2Subframe 2 provides
Page 48 and 49: Table 3.5-1. Subframe 2 Parameters
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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