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 | ostringstream prn;
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250 | prn << 'R' << setfill('0') << setw(2) << ee->almanac_number;
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251 | _prn = prn.str();
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252 |
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253 | _GPSweek = ee->GPSWeek;
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254 | _GPSweeks = ee->GPSTOW;
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255 |
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256 | _gps_utc = 0.0;
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257 | _E = ee->E;
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258 | _tau = ee->tau;
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259 | _gamma = ee->gamma;
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260 | _x_pos = ee->x_pos;
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261 | _x_velocity = ee->x_velocity;
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262 | _x_acceleration = ee->x_acceleration;
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263 | _y_pos = ee->y_pos;
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264 | _y_velocity = ee->y_velocity;
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265 | _y_acceleration = ee->y_acceleration;
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266 | _z_pos = ee->z_pos;
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267 | _z_velocity = ee->z_velocity;
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268 | _z_acceleration = ee->z_acceleration;
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269 | _health = 0;
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270 | _frequency_number = ee->frequency_number;
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271 | _tki = ee->tk;
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272 |
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273 | // Initialize status vector
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274 | // ------------------------
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275 | _tt = _GPSweeks;
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276 |
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277 | _xv(1) = _x_pos * 1.e3;
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278 | _xv(2) = _y_pos * 1.e3;
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279 | _xv(3) = _z_pos * 1.e3;
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280 | _xv(4) = _x_velocity * 1.e3;
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281 | _xv(5) = _y_velocity * 1.e3;
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282 | _xv(6) = _z_velocity * 1.e3;
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283 | }
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