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Adding tropospheric delay to Galileo PVT solution. Fixed computation of
the clock drift. Including relatisvistic effect in satellile clock drift, as it apperas on the ICDs
This commit is contained in:
Carles Fernandez
parent
901ff47621
commit
4dc8b055f7
@ -95,7 +95,7 @@ arma::vec galileo_e1_ls_pvt::rotateSatellite(double traveltime, arma::vec X_sat)
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//--- Find rotation angle --------------------------------------------------
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double omegatau;
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omegatau = OMEGA_EARTH_DOT * traveltime;
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omegatau = GALILEO_OMEGA_EARTH_DOT * traveltime;
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//--- Build a rotation matrix ----------------------------------------------
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arma::mat R3 = arma::zeros(3,3);
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@ -147,6 +147,9 @@ arma::vec galileo_e1_ls_pvt::leastSquarePos(arma::mat satpos, arma::vec obs, arm
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double rho2;
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double traveltime;
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double trop;
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double dlambda;
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double dphi;
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double h;
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arma::mat mat_tmp;
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arma::vec x;
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@ -179,6 +182,15 @@ arma::vec galileo_e1_ls_pvt::leastSquarePos(arma::mat satpos, arma::vec obs, arm
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&d_visible_satellites_Distance[i],
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pos.subvec(0,2),
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Rot_X - pos.subvec(0, 2));
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if(traveltime < 0.1 && nmbOfSatellites > 3)
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{
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//--- Find receiver's height
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togeod(&dphi, &dlambda, &h, 6378137.0, 298.257223563, pos(0), pos(1), pos(2));
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//--- Find delay due to troposphere (in meters)
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tropo(&trop, sin(d_visible_satellites_El[i] * GALILEO_PI/180.0), h/1000, 1013.0, 293.0, 50.0, 0.0, 0.0, 0.0);
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if(trop > 50.0 ) trop = 0.0;
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}
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}
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//--- Apply the corrections ----------------------------------------
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omc(i) = (obs(i) - norm(Rot_X - pos.subvec(0, 2), 2) - pos(3) - trop); // Armadillo
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@ -221,14 +233,12 @@ bool galileo_e1_ls_pvt::get_PVT(std::map<int,Gnss_Synchro> gnss_pseudoranges_map
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std::map<int,Galileo_Ephemeris>::iterator galileo_ephemeris_iter;
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int valid_pseudoranges = gnss_pseudoranges_map.size();
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arma::mat W = arma::eye(valid_pseudoranges, valid_pseudoranges); //channels weights matrix
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arma::mat W = arma::eye(valid_pseudoranges, valid_pseudoranges); // channels weights matrix
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arma::vec obs = arma::zeros(valid_pseudoranges); // pseudoranges observation vector
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arma::mat satpos = arma::zeros(3, valid_pseudoranges); //satellite positions matrix
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arma::mat satpos = arma::zeros(3, valid_pseudoranges); // satellite positions matrix
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int Galileo_week_number = 0;
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double utc = 0;
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double SV_clock_drift_s = 0;
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double SV_relativistic_clock_corr_s = 0;
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double TX_time_corrected_s;
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double SV_clock_bias_s = 0;
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@ -265,16 +275,12 @@ bool galileo_e1_ls_pvt::get_PVT(std::map<int,Gnss_Synchro> gnss_pseudoranges_map
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//to compute satellite position we need GST = WN+TOW (everything expressed in seconds)
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//double Rx_time = galileo_current_time + Galileo_week_number*sec_in_day*day_in_week;
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double Tx_time = Rx_time - gnss_pseudoranges_iter->second.Pseudorange_m/GALILEO_C_m_s;
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double Tx_time = Rx_time - gnss_pseudoranges_iter->second.Pseudorange_m / GALILEO_C_m_s;
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// 2- compute the clock drift using the clock model (broadcast) for this SV
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SV_clock_drift_s = galileo_ephemeris_iter->second.sv_clock_drift(Tx_time);
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// 2- compute the clock drift using the clock model (broadcast) for this SV, including relativistic effect
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SV_clock_bias_s = galileo_ephemeris_iter->second.sv_clock_drift(Tx_time);
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// 3- compute the relativistic clock drift using the clock model (broadcast) for this SV
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SV_relativistic_clock_corr_s = galileo_ephemeris_iter->second.sv_clock_relativistic_term(Tx_time);
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// 4- compute the current ECEF position for this SV using corrected TX time
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SV_clock_bias_s = SV_clock_drift_s + SV_relativistic_clock_corr_s;
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// 3- compute the current ECEF position for this SV using corrected TX time
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TX_time_corrected_s = Tx_time - SV_clock_bias_s;
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galileo_ephemeris_iter->second.satellitePosition(TX_time_corrected_s);
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@ -282,8 +288,8 @@ bool galileo_e1_ls_pvt::get_PVT(std::map<int,Gnss_Synchro> gnss_pseudoranges_map
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satpos(1,obs_counter) = galileo_ephemeris_iter->second.d_satpos_Y;
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satpos(2,obs_counter) = galileo_ephemeris_iter->second.d_satpos_Z;
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// 5- fill the observations vector with the corrected pseudoranges
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obs(obs_counter) = gnss_pseudoranges_iter->second.Pseudorange_m + SV_clock_bias_s*GALILEO_C_m_s;
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// 4- fill the observations vector with the corrected pseudoranges
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obs(obs_counter) = gnss_pseudoranges_iter->second.Pseudorange_m + SV_clock_bias_s * GALILEO_C_m_s;
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d_visible_satellites_IDs[valid_obs] = galileo_ephemeris_iter->second.i_satellite_PRN;
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d_visible_satellites_CN0_dB[valid_obs] = gnss_pseudoranges_iter->second.CN0_dB_hz;
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valid_obs++;
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@ -530,8 +536,8 @@ void galileo_e1_ls_pvt::cart2geo(double X, double Y, double Z, int elipsoid_sele
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}
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}
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while (abs(h - oldh) > 1.0e-12);
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d_latitude_d = phi * 180.0 / GPS_PI;
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d_longitude_d = lambda * 180 / GPS_PI;
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d_latitude_d = phi * 180.0 / GALILEO_PI;
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d_longitude_d = lambda * 180 / GALILEO_PI;
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d_height_m = h;
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}
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@ -672,7 +678,7 @@ void galileo_e1_ls_pvt::topocent(double *Az, double *El, double *D, arma::vec x,
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double lambda;
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double phi;
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double h;
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double dtr = GPS_PI/180.0;
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double dtr = GALILEO_PI/180.0;
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double a = 6378137.0; // semi-major axis of the reference ellipsoid WGS-84
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double finv = 298.257223563; // inverse of flattening of the reference ellipsoid WGS-84
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@ -727,3 +733,103 @@ void galileo_e1_ls_pvt::topocent(double *Az, double *El, double *D, arma::vec x,
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*D = sqrt(dx(0)*dx(0) + dx(1)*dx(1) + dx(2)*dx(2));
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}
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void galileo_e1_ls_pvt::tropo(double *ddr_m, double sinel, double hsta_km, double p_mb, double t_kel, double hum, double hp_km, double htkel_km, double hhum_km)
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{
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/* Inputs:
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sinel - sin of elevation angle of satellite
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hsta_km - height of station in km
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p_mb - atmospheric pressure in mb at height hp_km
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t_kel - surface temperature in degrees Kelvin at height htkel_km
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hum - humidity in % at height hhum_km
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hp_km - height of pressure measurement in km
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htkel_km - height of temperature measurement in km
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hhum_km - height of humidity measurement in km
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Outputs:
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ddr_m - range correction (meters)
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Reference
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Goad, C.C. & Goodman, L. (1974) A Modified Hopfield Tropospheric
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Refraction Correction Model. Paper presented at the
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American Geophysical Union Annual Fall Meeting, San
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Francisco, December 12-17
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Translated to C++ by Carles Fernandez from a Matlab implementation by Kai Borre
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*/
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const double a_e = 6378.137; // semi-major axis of earth ellipsoid
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const double b0 = 7.839257e-5;
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const double tlapse = -6.5;
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const double em = -978.77 / (2.8704e6 * tlapse * 1.0e-5);
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double tkhum = t_kel + tlapse * (hhum_km - htkel_km);
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double atkel = 7.5*(tkhum - 273.15) / (237.3 + tkhum - 273.15);
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double e0 = 0.0611 * hum * pow(10, atkel);
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double tksea = t_kel - tlapse * htkel_km;
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double tkelh = tksea + tlapse * hhum_km;
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double e0sea = e0 * pow((tksea / tkelh), (4 * em));
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double tkelp = tksea + tlapse * hp_km;
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double psea = p_mb * pow((tksea / tkelp), em);
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if(sinel < 0) { sinel = 0.0; }
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double tropo_delay = 0.0;
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bool done = false;
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double refsea = 77.624e-6 / tksea;
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double htop = 1.1385e-5 / refsea;
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refsea = refsea * psea;
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double ref = refsea * pow(((htop - hsta_km) / htop), 4);
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double a;
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double b;
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double rtop;
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while(1)
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{
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rtop = pow((a_e + htop), 2) - pow((a_e + hsta_km), 2) * (1 - pow(sinel, 2));
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// check to see if geometry is crazy
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if(rtop < 0) { rtop = 0; }
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rtop = sqrt(rtop) - (a_e + hsta_km) * sinel;
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a = -sinel / (htop - hsta_km);
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b = -b0 * (1 - pow(sinel,2)) / (htop - hsta_km);
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arma::vec rn = arma::vec(8);
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rn.zeros();
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for(int i = 0; i<8; i++)
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{
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rn(i) = pow(rtop, (i+1+1));
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}
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arma::rowvec alpha = {2 * a, 2 * pow(a, 2) + 4 * b /3, a * (pow(a, 2) + 3 * b),
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pow(a, 4)/5 + 2.4 * pow(a, 2) * b + 1.2 * pow(b, 2), 2 * a * b * (pow(a, 2) + 3 * b)/3,
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pow(b, 2) * (6 * pow(a, 2) + 4 * b) * 1.428571e-1, 0, 0};
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if(pow(b, 2) > 1.0e-35)
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{
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alpha(6) = a * pow(b, 3) /2;
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alpha(7) = pow(b, 4) / 9;
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}
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double dr = rtop;
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arma::mat aux_ = alpha * rn;
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dr = dr + aux_(0, 0);
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tropo_delay = tropo_delay + dr * ref * 1000;
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if(done == true)
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{
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*ddr_m = tropo_delay;
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break;
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}
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done = true;
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refsea = (371900.0e-6 / tksea - 12.92e-6) / tksea;
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htop = 1.1385e-5 * (1255 / tksea + 0.05) / refsea;
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ref = refsea * e0sea * pow(((htop - hsta_km) / htop), 4);
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}
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}
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@ -62,6 +62,7 @@ private:
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arma::vec rotateSatellite(double traveltime, arma::vec X_sat);
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void topocent(double *Az, double *El, double *D, arma::vec x, arma::vec dx);
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void togeod(double *dphi, double *dlambda, double *h, double a, double finv, double X, double Y, double Z);
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void tropo(double *ddr_m, double sinel, double hsta_km, double p_mb, double t_kel, double hum, double hp_km, double htkel_km, double hhum_km);
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public:
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int d_nchannels; //!< Number of available channels for positioning
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int d_valid_observations; //!< Number of valid pseudorange observations (valid satellites)
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@ -189,7 +189,7 @@ arma::vec gps_l1_ca_ls_pvt::leastSquarePos(arma::mat satpos, arma::vec obs, arma
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togeod(&dphi, &dlambda, &h, 6378137.0, 298.257223563, pos(0), pos(1), pos(2));
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//--- Find delay due to troposphere (in meters)
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tropo(&trop, sin(d_visible_satellites_El[i] * GPS_PI/180.0), h/1000, 1013.0, 293.0, 50.0, 0.0, 0.0, 0.0);
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tropo(&trop, sin(d_visible_satellites_El[i] * GPS_PI / 180.0), h / 1000, 1013.0, 293.0, 50.0, 0.0, 0.0, 0.0);
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if(trop > 50.0 ) trop = 0.0;
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}
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}
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@ -238,13 +238,11 @@ bool gps_l1_ca_ls_pvt::get_PVT(std::map<int,Gnss_Synchro> gnss_pseudoranges_map,
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int valid_pseudoranges = gnss_pseudoranges_map.size();
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arma::mat W = arma::eye(valid_pseudoranges, valid_pseudoranges); //channels weights matrix
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arma::vec obs = arma::zeros(valid_pseudoranges); // pseudoranges observation vector
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arma::mat satpos = arma::zeros(3, valid_pseudoranges); //satellite positions matrix
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arma::vec obs = arma::zeros(valid_pseudoranges); // pseudoranges observation vector
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arma::mat satpos = arma::zeros(3, valid_pseudoranges); //satellite positions matrix
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int GPS_week = 0;
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double utc = 0;
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double SV_clock_drift_s = 0;
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double SV_relativistic_clock_corr_s = 0;
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double TX_time_corrected_s;
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double SV_clock_bias_s = 0;
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@ -271,16 +269,12 @@ bool gps_l1_ca_ls_pvt::get_PVT(std::map<int,Gnss_Synchro> gnss_pseudoranges_map,
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// COMMON RX TIME PVT ALGORITHM MODIFICATION (Like RINEX files)
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// first estimate of transmit time
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double Rx_time = GPS_current_time;
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double Tx_time = Rx_time - gnss_pseudoranges_iter->second.Pseudorange_m/GPS_C_m_s;
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double Tx_time = Rx_time - gnss_pseudoranges_iter->second.Pseudorange_m / GPS_C_m_s;
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// 2- compute the clock drift using the clock model (broadcast) for this SV
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SV_clock_drift_s = gps_ephemeris_iter->second.sv_clock_drift(Tx_time);
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// 2- compute the clock drift using the clock model (broadcast) for this SV, including relativistic effect
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SV_clock_bias_s = gps_ephemeris_iter->second.sv_clock_drift(Tx_time); //- gps_ephemeris_iter->second.d_TGD;
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// 3- compute the relativistic clock drift using the clock model (broadcast) for this SV
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SV_relativistic_clock_corr_s = gps_ephemeris_iter->second.sv_clock_relativistic_term(Tx_time);
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// 4- compute the current ECEF position for this SV using corrected TX time
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SV_clock_bias_s = SV_clock_drift_s + SV_relativistic_clock_corr_s - gps_ephemeris_iter->second.d_TGD;
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// 3- compute the current ECEF position for this SV using corrected TX time
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TX_time_corrected_s = Tx_time - SV_clock_bias_s;
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gps_ephemeris_iter->second.satellitePosition(TX_time_corrected_s);
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@ -288,8 +282,8 @@ bool gps_l1_ca_ls_pvt::get_PVT(std::map<int,Gnss_Synchro> gnss_pseudoranges_map,
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satpos(1, obs_counter) = gps_ephemeris_iter->second.d_satpos_Y;
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satpos(2, obs_counter) = gps_ephemeris_iter->second.d_satpos_Z;
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// 5- fill the observations vector with the corrected pseudorranges
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obs(obs_counter) = gnss_pseudoranges_iter->second.Pseudorange_m + SV_clock_bias_s*GPS_C_m_s;
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// 4- fill the observations vector with the corrected pseudoranges
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obs(obs_counter) = gnss_pseudoranges_iter->second.Pseudorange_m + SV_clock_bias_s * GPS_C_m_s;
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d_visible_satellites_IDs[valid_obs] = gps_ephemeris_iter->second.i_satellite_PRN;
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d_visible_satellites_CN0_dB[valid_obs] = gnss_pseudoranges_iter->second.CN0_dB_hz;
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valid_obs++;
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@ -301,7 +295,7 @@ bool gps_l1_ca_ls_pvt::get_PVT(std::map<int,Gnss_Synchro> gnss_pseudoranges_map,
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<< " [m] Z=" << gps_ephemeris_iter->second.d_satpos_Z
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<< " [m] PR_obs=" << obs(obs_counter) << " [m]";
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// compute the UTC time for this SV (just to print the asociated UTC timestamp)
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// compute the UTC time for this SV (just to print the associated UTC timestamp)
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GPS_week = gps_ephemeris_iter->second.i_GPS_week;
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utc = gps_utc_model.utc_time(TX_time_corrected_s, GPS_week);
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}
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@ -749,7 +743,7 @@ void gps_l1_ca_ls_pvt::tropo(double *ddr_m, double sinel, double hsta_km, double
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const double em = -978.77 / (2.8704e6 * tlapse * 1.0e-5);
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double tkhum = t_kel + tlapse * (hhum_km - htkel_km);
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double atkel = 7.5*(tkhum - 273.15) / (237.3 + tkhum - 273.15);
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double atkel = 7.5 * (tkhum - 273.15) / (237.3 + tkhum - 273.15);
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double e0 = 0.0611 * hum * pow(10, atkel);
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double tksea = t_kel - tlapse * htkel_km;
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double tkelh = tksea + tlapse * hhum_km;
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@ -46,7 +46,7 @@ const double GALILEO_GM = 3.986004418e14; //!< Geocentric gravitational constan
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const double GALILEO_OMEGA_EARTH_DOT = 7.2921151467e-5; //!< Mean angular velocity of the Earth [rad/s]
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const double GALILEO_C_m_s = 299792458.0; //!< The speed of light, [m/s]
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const double GALILEO_C_m_ms = 299792.4580; //!< The speed of light, [m/ms]
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const double GALILEO_F = -4.442807633e-10; //!< Constant, [s/(m)^(1/2)]
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const double GALILEO_F = -4.442807309e-10; //!< Constant, [s/(m)^(1/2)]
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// carrier and code frequencies
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const double Galileo_E1_FREQ_HZ = 1.57542e9; //!< Galileo E1 carrier frequency [Hz]
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@ -106,7 +106,7 @@ double Galileo_Ephemeris::sv_clock_drift(double transmitTime)
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// Satellite Time Correction Algorithm, ICD 5.1.4
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double dt;
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dt = transmitTime - t0c_4;
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Galileo_satClkDrift = af0_4 + af1_4*dt + (af2_4 * dt)*(af2_4 * dt) + Galileo_dtr;
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Galileo_satClkDrift = af0_4 + af1_4 * dt + af2_4 * (dt * dt) + sv_clock_relativistic_term(transmitTime); //+Galileo_dtr;
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return Galileo_satClkDrift;
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}
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@ -137,7 +137,7 @@ double Gps_Ephemeris::sv_clock_drift(double transmitTime)
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{
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double dt;
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dt = check_t(transmitTime - d_Toc);
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d_satClkDrift = d_A_f0 + d_A_f1*dt + (d_A_f2 * dt)*(d_A_f2 * dt);
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d_satClkDrift = d_A_f0 + d_A_f1 * dt + d_A_f2 * (dt * dt) + sv_clock_relativistic_term(transmitTime);
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||||
return d_satClkDrift;
|
||||
}
|
||||
|
||||
|
||||
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Reference in New Issue
Block a user