| 1 | #include <math.h>
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| 2 | #include <sstream>
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| 3 | #include <iomanip>
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| 4 | #include <cstring>
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| 5 |
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| 6 | #include "ephemeris.h"
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| 7 | #include "bncutils.h"
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| 8 | #include "timeutils.h"
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| 9 |
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| 10 | using namespace std;
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| 11 |
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| 12 | //
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| 13 | ////////////////////////////////////////////////////////////////////////////
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| 14 | bool t_eph::isNewerThan(const t_eph* eph) const {
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| 15 | if (_GPSweek > eph->_GPSweek ||
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| 16 | (_GPSweek == eph->_GPSweek && _GPSweeks > eph->_GPSweeks)) {
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| 17 | return true;
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| 18 | }
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| 19 | else {
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| 20 | return false;
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| 21 | }
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| 22 | }
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| 23 |
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| 24 | // Set GPS Satellite Position
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| 25 | ////////////////////////////////////////////////////////////////////////////
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| 26 | void t_ephGPS::set(const gpsephemeris* ee) {
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| 27 | ostringstream prn;
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| 28 | prn << 'G' << setfill('0') << setw(2) << ee->satellite;
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| 29 |
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| 30 | _prn = prn.str();
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| 31 |
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| 32 | // TODO: check if following two lines are correct
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| 33 | _GPSweek = ee->GPSweek;
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| 34 | _GPSweeks = ee->TOE;
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| 35 |
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| 36 | _TOW = ee->TOW;
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| 37 | _TOC = ee->TOC;
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| 38 | _TOE = ee->TOE;
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| 39 | _IODE = ee->IODE;
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| 40 | _IODC = ee->IODC;
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| 41 |
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| 42 | _clock_bias = ee->clock_bias ;
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| 43 | _clock_drift = ee->clock_drift ;
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| 44 | _clock_driftrate = ee->clock_driftrate;
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| 45 |
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| 46 | _Crs = ee->Crs;
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| 47 | _Delta_n = ee->Delta_n;
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| 48 | _M0 = ee->M0;
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| 49 | _Cuc = ee->Cuc;
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| 50 | _e = ee->e;
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| 51 | _Cus = ee->Cus;
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| 52 | _sqrt_A = ee->sqrt_A;
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| 53 | _Cic = ee->Cic;
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| 54 | _OMEGA0 = ee->OMEGA0;
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| 55 | _Cis = ee->Cis;
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| 56 | _i0 = ee->i0;
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| 57 | _Crc = ee->Crc;
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| 58 | _omega = ee->omega;
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| 59 | _OMEGADOT = ee->OMEGADOT;
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| 60 | _IDOT = ee->IDOT;
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| 61 |
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| 62 | _TGD = ee->TGD;
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| 63 | }
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| 64 |
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| 65 | // Compute GPS Satellite Position (virtual)
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| 66 | ////////////////////////////////////////////////////////////////////////////
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| 67 | void t_ephGPS::position(int GPSweek, double GPSweeks,
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| 68 | double* xc,
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| 69 | double* vv) const {
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| 70 |
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| 71 | static const double secPerWeek = 7 * 86400.0;
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| 72 | static const double omegaEarth = 7292115.1467e-11;
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| 73 | static const double gmWGS = 398.6005e12;
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| 74 |
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| 75 | memset(xc, 0, 4*sizeof(double));
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| 76 | memset(vv, 0, 3*sizeof(double));
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| 77 |
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| 78 | double a0 = _sqrt_A * _sqrt_A;
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| 79 | if (a0 == 0) {
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| 80 | return;
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| 81 | }
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| 82 |
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| 83 | double n0 = sqrt(gmWGS/(a0*a0*a0));
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| 84 | double tk = GPSweeks - _TOE;
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| 85 | if (GPSweek != _GPSweek) {
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| 86 | tk += (GPSweek - _GPSweek) * secPerWeek;
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| 87 | }
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| 88 | double n = n0 + _Delta_n;
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| 89 | double M = _M0 + n*tk;
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| 90 | double E = M;
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| 91 | double E_last;
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| 92 | do {
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| 93 | E_last = E;
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| 94 | E = M + _e*sin(E);
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| 95 | } while ( fabs(E-E_last)*a0 > 0.001 );
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| 96 | double v = 2.0*atan( sqrt( (1.0 + _e)/(1.0 - _e) )*tan( E/2 ) );
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| 97 | double u0 = v + _omega;
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| 98 | double sin2u0 = sin(2*u0);
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| 99 | double cos2u0 = cos(2*u0);
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| 100 | double r = a0*(1 - _e*cos(E)) + _Crc*cos2u0 + _Crs*sin2u0;
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| 101 | double i = _i0 + _IDOT*tk + _Cic*cos2u0 + _Cis*sin2u0;
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| 102 | double u = u0 + _Cuc*cos2u0 + _Cus*sin2u0;
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| 103 | double xp = r*cos(u);
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| 104 | double yp = r*sin(u);
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| 105 | double OM = _OMEGA0 + (_OMEGADOT - omegaEarth)*tk -
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| 106 | omegaEarth*_TOE;
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| 107 |
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| 108 | double sinom = sin(OM);
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| 109 | double cosom = cos(OM);
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| 110 | double sini = sin(i);
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| 111 | double cosi = cos(i);
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| 112 | xc[0] = xp*cosom - yp*cosi*sinom;
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| 113 | xc[1] = xp*sinom + yp*cosi*cosom;
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| 114 | xc[2] = yp*sini;
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| 115 |
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| 116 | double tc = GPSweeks - _TOC;
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| 117 | if (GPSweek != _GPSweek) {
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| 118 | tc += (GPSweek - _GPSweek) * secPerWeek;
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| 119 | }
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| 120 | xc[3] = _clock_bias + _clock_drift*tc + _clock_driftrate*tc*tc
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| 121 | - 4.442807633e-10 * _e * sqrt(a0) *sin(E);
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| 122 |
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| 123 | // Velocity
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| 124 | // --------
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| 125 | double tanv2 = tan(v/2);
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| 126 | double dEdM = 1 / (1 - _e*cos(E));
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| 127 | double dotv = sqrt((1.0 + _e)/(1.0 - _e)) / cos(E/2)/cos(E/2) / (1 + tanv2*tanv2)
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| 128 | * dEdM * n;
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| 129 | double dotu = dotv + (-_Cuc*sin2u0 + _Cus*cos2u0)*2*dotv;
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| 130 | double dotom = _OMEGADOT - omegaEarth;
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| 131 | double doti = _IDOT + (-_Cic*sin2u0 + _Cis*cos2u0)*2*dotv;
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| 132 | double dotr = a0 * _e*sin(E) * dEdM * n
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| 133 | + (-_Crc*sin2u0 + _Crs*cos2u0)*2*dotv;
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| 134 | double dotx = dotr*cos(u) - r*sin(u)*dotu;
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| 135 | double doty = dotr*sin(u) + r*cos(u)*dotu;
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| 136 |
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| 137 | vv[0] = cosom *dotx - cosi*sinom *doty // dX / dr
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| 138 | - xp*sinom*dotom - yp*cosi*cosom*dotom // dX / dOMEGA
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| 139 | + yp*sini*sinom*doti; // dX / di
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| 140 |
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| 141 | vv[1] = sinom *dotx + cosi*cosom *doty
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| 142 | + xp*cosom*dotom - yp*cosi*sinom*dotom
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| 143 | - yp*sini*cosom*doti;
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| 144 |
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| 145 | vv[2] = sini *doty + yp*cosi *doti;
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| 146 | }
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| 147 |
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| 148 |
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| 149 | // Derivative of the state vector using a simple force model (static)
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| 150 | ////////////////////////////////////////////////////////////////////////////
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| 151 | ColumnVector t_ephGlo::glo_deriv(double /* tt */, const ColumnVector& xv) {
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| 152 |
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| 153 | // State vector components
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| 154 | // -----------------------
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| 155 | ColumnVector rr = xv.rows(1,3);
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| 156 | ColumnVector vv = xv.rows(4,6);
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| 157 |
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| 158 | // Acceleration
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| 159 | // ------------
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| 160 | static const double GM = 398.60044e12;
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| 161 | static const double AE = 6378136.0;
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| 162 | static const double OMEGA = 7292115.e-11;
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| 163 | static const double C20 = -1082.63e-6;
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| 164 |
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| 165 | double rho = rr.norm_Frobenius();
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| 166 | double t1 = -GM/(rho*rho*rho);
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| 167 | double t2 = 3.0/2.0 * C20 * (GM*AE*AE) / (rho*rho*rho*rho*rho);
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| 168 | double t3 = OMEGA * OMEGA;
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| 169 | double t4 = 2.0 * OMEGA;
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| 170 | double z2 = rr(3) * rr(3);
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| 171 |
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| 172 | // Vector of derivatives
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| 173 | // ---------------------
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| 174 | ColumnVector va(6);
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| 175 | va(1) = vv(1);
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| 176 | va(2) = vv(2);
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| 177 | va(3) = vv(3);
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| 178 | va(4) = (t1 + t2*(1.0-5.0*z2/(rho*rho)) + t3) * rr(1) + t4*vv(2);
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| 179 | va(5) = (t1 + t2*(1.0-5.0*z2/(rho*rho)) + t3) * rr(2) - t4*vv(1);
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| 180 | va(6) = (t1 + t2*(3.0-5.0*z2/(rho*rho)) ) * rr(3);
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| 181 |
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| 182 | return va;
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| 183 | }
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| 184 |
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| 185 | // Compute Glonass Satellite Position (virtual)
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| 186 | ////////////////////////////////////////////////////////////////////////////
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| 187 | void t_ephGlo::position(int GPSweek, double GPSweeks,
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| 188 | double* xc, double* vv) const {
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| 189 |
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| 190 | static const double secPerWeek = 7 * 86400.0;
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| 191 | static const double nominalStep = 10.0;
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| 192 |
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| 193 | memset(xc, 0, 4*sizeof(double));
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| 194 | memset(vv, 0, 3*sizeof(double));
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| 195 |
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| 196 | double dtPos = GPSweeks - _tt;
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| 197 | if (GPSweek != _GPSweek) {
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| 198 | dtPos += (GPSweek - _GPSweek) * secPerWeek;
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| 199 | }
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| 200 |
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| 201 | int nSteps = int(fabs(dtPos) / nominalStep) + 1;
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| 202 | double step = dtPos / nSteps;
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| 203 |
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| 204 | for (int ii = 1; ii <= nSteps; ii++) {
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| 205 | _xv = rungeKutta4(_tt, _xv, step, glo_deriv);
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| 206 | _tt += step;
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| 207 | }
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| 208 |
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| 209 | // Position and Velocity
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| 210 | // ---------------------
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| 211 | xc[0] = _xv(1);
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| 212 | xc[1] = _xv(2);
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| 213 | xc[2] = _xv(3);
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| 214 |
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| 215 | vv[0] = _xv(4);
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| 216 | vv[1] = _xv(5);
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| 217 | vv[2] = _xv(6);
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| 218 |
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| 219 | // Clock Correction
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| 220 | // ----------------
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| 221 | double dtClk = GPSweeks - _GPSweeks;
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| 222 | if (GPSweek != _GPSweek) {
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| 223 | dtClk += (GPSweek - _GPSweek) * secPerWeek;
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| 224 | }
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| 225 | xc[3] = -_tau + _gamma * dtClk;
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| 226 | }
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| 227 |
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| 228 | // IOD of Glonass Ephemeris (virtual)
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| 229 | ////////////////////////////////////////////////////////////////////////////
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| 230 | int t_ephGlo::IOD() const {
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| 231 |
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| 232 | bool old = false;
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| 233 |
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| 234 | if (old) { // 5 LSBs of iod are equal to 5 LSBs of tb
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| 235 | unsigned int tb = int(fmod(_GPSweeks,86400.0)); //sec of day
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| 236 | const int shift = sizeof(tb) * 8 - 5;
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| 237 | unsigned int iod = tb << shift;
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| 238 | return (iod >> shift);
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| 239 | }
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| 240 | else {
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| 241 | return int(fmod(_tki, 3600)) / 30;
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| 242 | }
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| 243 | }
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| 244 |
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| 245 | // Set Glonass Ephemeris
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| 246 | ////////////////////////////////////////////////////////////////////////////
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| 247 | void t_ephGlo::set(const glonassephemeris* ee) {
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| 248 |
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| 249 | }
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