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

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3.5.4.2.3 User Algorithm for Application of the EOPThe EOP fields in subframe 3, page 2 contain the EOP needed to construct the ECEF-to-ECI coordinatetransformation. The user computes the ECEF position of the SV antenna phase center using the equations shown inTable 3.5-2. The coordinate transformation, for translating to the corresponding ECI SV antenna phase centerposition, is derived using the equations shown in Section 30.3.3.5.1.1 and Table 30-VIII of IS-GPS-200. Thecoordinate systems are defined in Section 20.3.3.4.3.3 of IS-GPS-200.Table 3.5-5.Earth Orientation ParametersParameterNo. ofBits**ScaleFactor(LSB)EffectiveRange***Unitst EOPPM_X †PM_XPM_Y ††PM_YUT1 †††UT1 †††EOP Data Reference TimeX-Axis Polar Motion Valueat Reference Time.X-Axis Polar Motion Drift atReference Time.Y-Axis Polar Motion Valueat Reference Time.Y-Axis Polar Motion Drift atReference Time.UT1-UTC Difference atReference Time.Rate of UT1-UTCDifference at ReferenceTime1621*15*21*15*31*19*2 42 -202 -212 -202 -212 -242 -25 604,78417.8125 x 10 -317.8125 x 10 -3647.8125 x 10 -3 secondsarc-secondsarc-seconds/dayarc-secondsarc-seconds/daysecondsseconds/day* Parameters so indicated are in two’s complement notation;** See Figure 3.5-3 for complete bit allocation in subframe 3, page 2;*** Unless otherwise indicated in this column, effective range is the maximum range attainable withindicated bit allocation and scale factor.†Represents the predicted angular displacement of instantaneous Celestial Ephemeris Pole with respect tosemi-minor axis of the reference ellipsoid along Greenwich meridian.††Represents the predicted angular displacement of instantaneous Celestial Ephemeris Pole with respect tosemi-minor axis of the reference ellipsoid on a line directed 90 west of Greenwich meridian.†††With zonal tides restored.56 IS-GPS-800A8 June 2010
3.5.4.3 Subframe 3, Page 3 & Page 4 – AlmanacThe almanac parameters are provided in any one of subframe 3, pages 3 and 4. Page 3 provides the reducedalmanac parameters and Midi almanac parameters are provided in page 4. The reduced almanac parameters (i.e.subframe 3, page 3) for the complete set of SVs in the constellation will be broadcast by a SV using shorter durationof time compared to the broadcast of the complete set of Midi almanac parameters (i.e. subframe 3, page 4). Theparameters are defined below, followed by material pertinent to the use of the data.3.5.4.3.1 Almanac Reference WeekBits 15 through 27 of subframe 3, pages 3 and 4 shall indicate the number of the week (WN a-n ) to which the almanacreference time (t oa ) is referenced (see paragraph 3.5.4.3.2). The WN a-n term consists of 13 bits which shall be amodulo-8192 binary representation of the GPS week number (see paragraph 6.2.2) to which the t oa is referenced.Bits 28 through 35 of subframe 3, pages 3 and 4 shall contain the value of t oa , which is referenced to this WN a-n .3.5.4.3.2 Almanac Reference TimeSee paragraph 20.3.3.5.2.2 of IS-GPS-200.3.5.4.3.3 SV PRN NumberBits 36 through 43 of subframe 3, page 4 and bits 1 through 8 in each packet of reduced almanac shall specify PRNnumber of the SV whose almanac or reduced almanac, respectively, is provided in the message or in the packet.3.5.4.3.4 Signal Health (L1/L2/L5)The three, one-bit, health indication in bits 44, 45 and 46 of subframe 3, page 4 and bits 31, 32 and 33 of each packetof reduced almanac refers to the L1, L2, and L5 signals of the SV whose PRN number is specified in the message orin the packet. For each health indicator, a “0” signifies that all navigation data are valid and “1” signifies that someor all navigation data are invalid. The predicted health data will be updated at the time of upload when a newreduced almanac has been built by the CS. The transmitted health data may not correspond to the actual health ofthe transmitting SV or other SVs in the constellation.3.5.4.3.5 Reduced Almanac DataSubframe 3, page 3, Figure 3.5-4, shall contain reduced almanac data packets for 6 SVs. The reduced almanac dataof a SV is broadcast in a packet of 33 bits long, as described in Figure 3.5-9. The reduced almanac data are a subsetof the almanac data which provide an ephemeris with less precision than that derived from parameters in subframe2. The reduced almanac data values are provided relative to pre-specified reference values. The bit lengths, scalefactors, ranges, and units of the reduced almanac parameters are given in Table 3.5-6.The reduced almanac parameters shall be updated by the CS at least once every 3 days while the CS is able toupload the SVs. If the CS is unable to upload the SVs then the accuracy of the reduced almanac parameters57 IS-GPS-800A8 June 2010
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IS-GPS-800A8 June 2010GLOBAL POSITI
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REVISION RECORDLTR DESCRIPTION DATE
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3.2.3.3 Cyclic Redundancy Check ...
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LIST OF FIGURESFigure 3.2-1. Genera
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1. INTRODUCTION1.1 ScopeThis Interf
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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 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 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
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PRNSignalNo.Table 6.3-2. Additional
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PRNSignalNo.Table 6.3-2 Additional
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