IS-GPS-705D (797936), страница 11

Просмтор этого файла доступен только зарегистрированным пользователям. Но у нас супер быстрая регистрация: достаточно только электронной почты!

Текст из файла (страница 11)

Bits 72 to 127 contain SV clock correction coefficients. Therelated algorithm is given in paragraph 20.3.3.2.3.20.3.3.2.1.2 Data Predict Time of Week.Bits 39 through 49 of message types 30 through 37 shall contain the data predict time of week(top). The top term provides the epoch time of week of the state estimate utilized for theprediction of SV clock correction coefficients.20.3.3.2.2 Clock Parameter Characteristics.The number of bits, the scale factors of the LSB (which is the last bit received), the range, andthe units of clock correction parameters shall be as specified in Table 20-III.20.3.3.2.3 User Algorithms for SV Clock Correction Data.The algorithms defined in paragraph 20.3.3.3.3.1 of IS-GPS-200 allow all users to correct thecode phase time received from the SV with respect to both SV code phase offset and relativisticeffects.

However, since the SV clock corrections of equations in paragraph 20.3.3.3.3.1 of ISGPS-200 are estimated by the CS using dual frequency L1 and L2 P(Y) code measurements, thesingle-frequency L5 user and the dual-frequency L1 and L5, and L2 and L5 users must applyadditional terms to the SV clock corrections equations.

These terms are described in paragraph20.3.3.3.1.65IS-GPS-705D24 Sep 2013Table 20-III. Clock Correction and Accuracy ParametersParameterSymboltocNo. ofBits**11Parameter DescriptionClock Data Reference Time of WeekScaleFactor(LSB)300EffectiveRange***604,500UnitssecondsURANED0 IndexNED Accuracy Index5*(see text)URANED1 IndexNED Accuracy Change Index3(see text)URANED2 IndexNED Accuracy Change Rate Index3(see text)af2-nSV ClockCoefficientDriftRateCorrectionaf1-n10*2-60sec/sec220*2-48sec/sec26*2-35secondsSV Clock Drift Correction Coefficientaf0-nSV Clock Bias Correction Coefficient******Parameters so indicated are two’s complement, with the sign bit (+ or -) occupying the MSB;See Figures 20-3 through 20-10 for complete bit allocation in message types 30 to 37;Unless otherwise indicated in this column, effective range is the maximum range attainable withindicated bit allocation and scale factor.20.3.3.2.4 Non-Elevation-Dependent (NED) Accuracy EstimatesBits 50 through 54, and 55 through 57, and 58 through 60 of message types 30 through 37 shallcontain the non-elevation-dependent (NED) component URANED0 Index,URANED1 Index, andURANED2 Index, respectively, of the SV (reference paragraph 6.2.1) for the unauthorized user.The following equations together with the broadcast URANED0 Index, URANED1 Index, andURANED2 Index shall give the clock-related user range accuracy of IAURANED over the currentclock/ephemeris fit interval.

While the actual NED-related URA may vary over the satellitefootprint, the IAURANED calculated using the parameters in message type 10 at each instantduring the current clock/ephemeris fit interval shall bound the maximum IAURANED expectedfor the worst-case location within the satellite footprint at that instant.The user shall calculate the NED-related URA with the equation (in meters);IAURANED = URANED0 + URANED1 (t - top + 604,800*(WN - WNop))for t - top + 604,800*(WN - WNop) ≤ 93,600 seconds66IS-GPS-705D24 Sep 2013IAURANED = URANED0 + URANED1*(t - top + 604,800*(WN - WNop)) + URANED2*(t - top +604,800*(WN - WNop) - 93,600)2for t - top + 604,800*(WN - WNop) > 93,600 secondswheret is the GPS system timeThe CS shall derive URANED0, URANED1, and URANED2 indexes which, when used together inthe above equations, results in the minimum IAURANED that is greater than the predictedIAURANED during the ephemeris fit interval.The user shall use the broadcast URANED0 index to derive the URANED0 value.

The URANED0index is a signed, two’s complement integer in the range of +15 to -16 and has the followingrelationship to the URANED0 value:URANED0 IndexURANED0 (meters)156144.00< URANED0(or no accuracy prediction is available)143072.00< URANED0≤6144.00131536.00< URANED0≤3072.0012768.00< URANED0≤1536.0011384.00< URANED0≤768.0010192.00< URANED0≤384.00996.00< URANED0≤192.00848.00< URANED0≤96.00724.00< URANED0≤48.00613.65< URANED0≤24.0067IS-GPS-705D24 Sep 201359.65< URANED0≤13.6546.85< URANED0≤9.6534.85< URANED0≤6.8523.40< URANED0≤4.8512.40< URANED0≤3.4001.70< URANED0≤2.40-11.20< URANED0≤1.70-20.85< URANED0≤1.20-30.60< URANED0≤0.85-40.43< URANED0≤0.60-50.30< URANED0≤0.43-60.21< URANED0≤0.30-70.15< URANED0≤0.21-80.11< URANED0≤0.15-90.08< URANED0≤0.11-100.06< URANED0≤0.08-110.04< URANED0≤0.06-120.03< URANED0≤0.04-130.02< URANED0≤0.03-140.01< URANED0≤0.02URANED0≤0.01-15-16No accuracy prediction available-use at own riskIntegrity properties of the URA are specified with respect to the upper bound values of the URAindex (see 20.3.3.1.1).68IS-GPS-705D24 Sep 2013For each URANED0 index (N), users may compute a nominal URANED0 value (X) as given by:• If the value of N is 6 or less, but more than -16, X = 2(1 + N/2),• If the value of N is 6 or more, but less than 15, X = 2(N - 2),• N = -16 or N = 15 shall indicate the absence of an accuracy prediction and shall advise thestandard positioning service user to use that SV at his own risk.For N = 1, 3, and 5, X should be rounded to 2.8, 5.7, and 11.3 meters, respectively.The nominal URANED0 value (X) shall be suitable for use as a conservative prediction of theRMS NED range errors for accuracy-related purposes in the pseudorange domain (e.g.,measurement de-weighting RAIM, FOM computations).

Integrity properties of the IAURANEDare specified with respect to the scaled (multiplied by either 4.42 or 5.73 as appropriate) upperbound values of the URANED0 index, URANED1 index, and URANED2 index (see 20.3.3.1.1).URANED0 accounts for zeroth order SIS contributions to user range error which include, but arenot limited to, the following: LSB representation/truncation error; the net effect of clockcorrection polynomial error and code phase error in the transmitted signal for single-frequencyL1C/A or single-frequency L2C users who correct the code phase as described in Section20.3.3.3.1.1.1; the net effect of clock parameter, code phase, and inter-signal correction error fordual-frequency L1/L2 and L1/L5 users who correct for group delay and ionospheric effects asdescribed in Section 20.3.3.3.1.1.2; radial ephemeris error; anisotropic antenna errors; and signaldeformation error. URANED does not account for user range contributions due to the inaccuracyof the broadcast ionospheric data parameters used in the single-frequency ionospheric model orfor other atmospheric effects.The transmitted URANED1 index is an integer value in the range 0 to 7.

The URA NED1 index hasthe following relationship to the URA NED1 value:1NURANED1 = 2 (meters/second)whereN= 14 + URANED1 Index.69IS-GPS-705D24 Sep 2013The transmitted URANED2 index is an integer value in the range 0 to 7. URANED2 index has thefollowing relationship to the URANED2:URANED21N= 2 (meters/second/second)whereN= 28 + URANED2 Index.20.3.3.3 Message Type 30 Ionospheric and Group Delay Correction Parameters.20.3.3.3.1 Message Type 30 Ionospheric and Group Delay Correction Parameter Content.Message type 30 provides SV clock correction parameters (ref. Section 20.3.3.2) and ionosphericand group delay correction parameters.

Bits 128 through 192 of message type 30 provide thegroup delay differential correction terms for L1, L2, and L5 signal users. Bits 193 through 256provide the ionospheric correction parameters for single frequency user. The followingalgorithms shall apply when interpreting the correction parameters in the message.20.3.3.3.1.1 Estimated L1-L2 Group Delay Differential.The group delay differential correction terms, TGD, ISCL1C/A, ISCL2C are contained in bits 128through 166 of message type 30.

See paragraph 30.3.3.3.1.1 of IS-GPS-200. The bit lengths,scale factors, ranges, and units of these parameters are given in Table 20-IV. These group delaydifferential correction terms are also used for the benefit of single frequency L5-I5 and L5-Q5users and dual frequency L1/L5 and L2/L5 users.20.3.3.3.1.1.1 L1/L2 Inter-Signal Group Delay Differential Correction.See paragraph 30.3.3.3.1.1.1 of IS-GPS-200.20.3.3.3.1.2 Estimated L5 Group Delay DifferentialThe group delay differential correction terms, TGD, ISCL5I5 and ISCL5Q5, for the benefit of singlefrequency L5-I5 and L5-Q5 users and dual frequency L1/L5 and L2/L5 users are contained inbits 128 through 140 and 167 through 192 of message type 30 (see Figure 20-3 for complete bitallocation). The bit lengths, scale factors, ranges, and units of these parameters are given inTable 20-IV.

Характеристики

Список файлов учебной работы