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

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3.5.3.6 Ephemeris Parameter CharacteristicsFor each ephemeris parameter contained in subframe 2, the bit lengths, scale factors, ranges, and units are given inTable 3.5-1. See Figure 3.5-1 for complete bit allocation in subframe 2.3.5.3.6.1 User Algorithm for Determination of SV PositionThe user shall compute the ECEF coordinates of position for the SV’s antenna phase center (APC) utilizing avariation of the equations shown in Table 3.5-2. The ephemeris parameters are Keplerian in appearance; however,the values of these parameters are produced by the SV via a least squares curve fit of the predicted ephemeris of theSV APC (time-position quadruples: t, x, y, z expressed in ECEF coordinates). Particulars concerning the applicablecoordinate system are given in Sections 20.3.3.4.3.3 and 20.3.3.4.3.4 of IS-GPS-200.The sensitivity of the SV’s position to small perturbations in most ephemeris parameters is extreme. The sensitivity ofposition to the parameters A, C rc-n , and C rs-n is about one meter/meter. The sensitivity of position to the angularparameters is on the order of 10 8 meters/semi-circle, and to the angular rate parameters is on the order of 10 12meters/semi-circle/second. Because of this extreme sensitivity to angular perturbations, the value of used in the curvefit is given here. is a mathematical constant, the ratio of a circle’s circumference to its diameter. Here is taken as3.1415926535898.44 IS-GPS-800A8 June 2010
Table 3.5-2. Elements of Coordinate System (part 1 of 2)Element/EquationDescription = 3.986005 x 10 14 meters 3 /sec 2WGS 84 value of the earth’s gravitational constant for GPS user e = 7.2921151467 x 10 -5 rad/secA 0 = A REF + A *A k = A 0 + (A) t kWGS 84 value of the earth’s rotation rateSemi-Major Axis at reference timeSemi-Major Axisn 0 =3A 0Computed Mean Motion (rad/sec)t k = t – t oe **n A = n 0 +½ ∆n 0 t kn A = n 0 + n AM k = M 0 + n A t kM k = E k – e n sin E kTime from ephemeris reference timeMean motion difference from computed valueCorrected Mean MotionMean AnomalyKepler’s equation for Eccentric Anomaly (radians)(may be solved by iteration) k = tan -1 sin coskk True Anomaly 2 = tan -1 1e n sin E k / 1e n cos E k cos E e / 1e cos E knnkE k = cos -1 e n cos 1e n cos kk Eccentric Anomaly* A REF = 26,559,710 meters** t is GPS system time at time of transmission, i.e., GPS time corrected for transit time (range/speed of light).Furthermore, t k shall be the actual total difference between the time t and the epoch time t oe , and must accountfor beginning or end of week crossovers. That is if t k is greater than 302,400 seconds, subtract 604,800seconds from t k . If t k is less than -302,400 seconds, add 604,800 seconds to t k .45 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 50 and 51: 3.5.3.1 Transmission Week NumberBit
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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