//***********************************************************************************
//Filename: SatellitePosition.cpp
//
//Date Author Revison History
//05/08/2017 Guled Sheikh version 1
//
//***********************************************************************************
//
//Copyright 2017~2018. All Rights Reserved
//
//***********************************************************************************
#include "SatellitePosition.h"
//Computes the Euclidean distance
double SatellitePosition::EucldNorm(double x, double y, double z)
{
double norm = sqrt(pow(x, 2) + pow(y, 2) + pow(z, 2));
return norm;
}
// Fucntion that returns satellite positions corrected for Earth rotation errors
vector<double> SatellitePosition::EarthRot_Corr(double time, vector<double> pos)
{
/*...Returns rotated satellite ECEF coordinates due to Earth rotation during signal travel time
/*....time represents the travel time...*/
/*....WGS 84 value of the earth's rotation rate (rad/sec)...*/
double OMEGA_e = 7.2921151467e-5;
double OMEGA_tau = OMEGA_e*time;
Eigen::Matrix3d R3;
Eigen::Vector3d POS_ROT;
Eigen::Vector3d POS(pos[0], pos[1], pos[2]);
vector <double> POSITION;
double R11, R12, R13, R21, R22, R23, R31, R32, R33;
R11 = cos(OMEGA_tau); R21 = -sin(OMEGA_tau); R31 = 0;
R12 = sin(OMEGA_tau); R22 = cos(OMEGA_tau); R32 = 0;
R13 = 0; R23 = 0; R33 = 1;
R3 << R11, R12, R13,
R21, R22, R23,
R31, R32, R33;
POS_ROT = R3*POS;
POSITION.push_back(POS_ROT[0]);
POSITION.push_back(POS_ROT[1]);
POSITION.push_back(POS_ROT[2]);
return POSITION;
}
// Function that corrects for tropospheric effects
double SatellitePosition::Tropo_Corr(vector<double> pos, vector<double> ini_pos)
{
Eigen::Vector3d POS(pos[0], pos[1], pos[2]);
Eigen::Vector3d INI_POS(ini_pos[0], ini_pos[1], ini_pos[2]);
double dtrop;
double tot_p = 1013; // Mbar
double pwv = 16; //Mbar
double pd = tot_p - pwv; // Mbar
double T = 300; // Kelvins
double R = 6371e3;
double sat_pos_norm = EucldNorm(pos[0], pos[1], pos[2]);
double rec_pos_norm = EucldNorm(ini_pos[0], ini_pos[1], ini_pos[2]);
double g = acos((POS.dot(INI_POS)) / (sat_pos_norm*rec_pos_norm));
double e = atan((sat_pos_norm*cos(g) - R) / (sat_pos_norm*sin(g)));
//cout << (e*180)/ PI << endd;
//cin.get();
double z = (PI / 2) - e;
if (z == 0) {
dtrop = (0.002277 / cos(z))*(pd + (((1255 / T) + 0.05)*pwv));
}
else {
dtrop = (0.002277 / cos(z))*(pd + (((1255 / T) + 0.05)*pwv) - (1.16*(pow(tan(z), 2))));
}
return dtrop;
}
// This function removes effects of ionosphere based on the iono-free model
double SatellitePosition::iono_free(double count)
{
double gamma = pow((1575.42 / 1227.6), 2);
double P1_temp = 0.0, P2_temp = 0.0, PR_temp = 0.0, C1_temp = 0.0;
// Finding the pseudoranges
if (find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "P1") - RinexFile->head.obstype.begin() != 0) {
ptrdiff_t pos_P1 = find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "P1") - RinexFile->head.obstype.begin();
if (pos_P1 == RinexFile->head.obstype.size()) {
}
else {
P1_temp = RinexFile->obs.record[count][pos_P1];
}
}
if (find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "P2") - RinexFile->head.obstype.begin() != 0) {
ptrdiff_t pos_P2 = find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "P2") - RinexFile->head.obstype.begin();
if (pos_P2 == RinexFile->head.obstype.size()) {
}
else {
P2_temp = RinexFile->obs.record[count][pos_P2];
}
}
if (P2_temp != 0 && P1_temp != 0) {
PR_temp = (P2_temp - (gamma*P1_temp)) / (1 - gamma);
}
else {
ptrdiff_t pos_PR = find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "C1") - RinexFile->head.obstype.begin();
PR_temp = RinexFile->obs.record[count][pos_PR];
}
return PR_temp;
}
// This function removes effects of ionosphere based on the Klobuchar model
double SatellitePosition::klobuchar(double fi, double lambda, double elev, double azimuth, double tow)
{
VectorXd alfa;
VectorXd beta;
alfa << 9.3132e-09, 1.4901e-08, -5.9605e-08, -1.1921e-07;
beta << 8.8064e+04, 4.9152e+04, -1.3107e+05, -3.2768e+05;
double c = 299792458, deg2semi = 1.0 / 180.0, semi2rad = PI, deg2rad = PI / 180.0, dIon1;
double a = azimuth*deg2rad; // asimuth in radians
double e = elev*deg2semi; // elevation angle in semicircles
double psi = 0.0137 / (e + 0.11) - 0.022; //Earth Centered angle
double lat_i = fi*deg2semi + psi*cos(a); // Subionospheric lat
if (lat_i > 0.416) { lat_i = 0.416; }
else if (lat_i < -0.416) { lat_i = -0.416; }
//Subionospheric long
double long_i = lambda*deg2semi + (psi*sin(a) / cos(lat_i*semi2rad));
// Geomagnetic latitude
double lat_m = lat_i + 0.064*cos((long_i - 1.617)*semi2rad);
double t = 4.32e4*long_i + tow;
t = fmod(t, 86400.0); // Seconds of day
if (t > 86400.0) { t = t - 86400.0; }
if (t < 86400.0) { t = t + 86400.0; }
double sF = 1.0 + 16.0* pow((0.53 - e), 3); // Slant factor
// Period of model
double PER = beta(0) + beta(1)*lat_m + beta(2)* pow(lat_m, 2) + beta(3)* pow(lat_m, 3);
if (PER < 72000.0) { PER = 72000.0; }
double x = 2.0*PI*(t - 50400.0) / PER; // Phase of the model
double AMP = alfa(0) + alfa(1) *lat_m + alfa(2) * pow(lat_m, 2) + alfa(3) * pow(lat_m, 3); // Amplitud of the model
if (AMP < 0.0) { AMP = 0.0; }
if (abs(x) > 1.57) { dIon1 = sF * (5.0e-9); }
else { dIon1 = sF * (5.0e-9 + AMP*(1.0 - x*x / 2.0 + x*x*x*x / 24.0)); }
return dIon1;
}
// This function computes the gps time in seconds
double SatellitePosition::gpstimeCalc(double year, double month, double day, double hour, double min, double sec)
{
double y, m, JD, gps_week, gps_seconds;
double secs_per_week = 604800; // Seconds in one week
//Converts the two digit year to a four digit year.
//Two digit year represents a year in the range 1980 - 2079.
if (year >= 80 && year <= 99) { year = 1900 + year; }
if (year >= 0 && year <= 79) { year = 2000 + year; }
//Calculates the 'm' term used below from the given calendar month.
if (month <= 2) { y = year - 1; m = month + 12; }
if (month > 2) { y = year; m = month; }
//Computes the Julian date corresponding to the given calendar date.
JD = floor((365.25 * y)) + floor((30.6001 * (m + 1))) +
day + ((hour + min / 60 + sec / 3600) / 24) + 1720981.5;
//Computes the GPS week corresponding to the given calendar date.
gps_week = floor((JD - 2444244.5) / 7);
//Computes the GPS seconds corresponding to the given calendar date.
gps_seconds = round(((((JD - 2444244.5) / 7) - gps_week)*secs_per_week) / 0.5)*0.5;
return gps_seconds;
}
//This functions corrects for tropospheric effects based on initial values given in the navigation file
double SatellitePosition::NMF_hyd(double sat_elev)
{
double A = 33.748;
double B = -0.782;
double A1 = 38.079;
double B1 = -0.8088;
double Y1 = A*pow(sat_elev, B);
double Y2 = A1*pow(sat_elev, B1);
double Y = Y1 + Y2;
return Y;
}
// This function initializes the observation and navigation filenames
void SatellitePosition::SetFilenames(const char * ObsFile, const char * NavFile)
{
size_t obs_size = strlen(ObsFile);
size_t nav_size = strlen(NavFile);
if (ObsFile != NULL) {
strcpy(obsFile, ObsFile);
}
if (NavFile != NULL) {
strcpy(navFile, NavFile);
}
obsFile[obs_size] = '\0';
navFile[nav_size] = '\0';
RinexFile = new reader(SatellitePosition::obsFile, SatellitePosition::navFile);
RinexFile->rinexNAVReader(RinexFile->SV_data);
}
//This function opens the observation and navigation files from the environment file
void SatellitePosition::OpenEnvFile(ENVI_FILE & envi_records, SatellitePosition & object1, SatellitePosition & object2)
{
Env_File = fopen("EnvFileGMIS.txt", "rt");
if (Env_File == NULL) perror("Error opening file");
char line[MAX_STRLEN];
fgets(line, MAX_STRLEN, Env_File);
while (!feof(Env_File)) {
if (sizeof(line) >= 61) {
if (strstr(line, "VERSION / TYPE")) {
string sline(line); // convert the line (char) to string class type sLine
string token = sline.substr(4, 4); // from 4th character and 4 spaces
envi_records.version = token;
}
if (strstr(line, "BASE FILE(OBS/NAV)")) {
std::istringstream iss(line);
std::vector<std::string> results((std::istream_iterator<std::string>(iss)),
std::istream_iterator<std::string>());
Filename1_Obs = results[0]; Filename1_Nav = results[1];
object1.SetFilenames(Filename1_Obs.c_str(), Filename1_Nav.c_str());
}
if (strstr(line, "ROVER FILE(OBS/NAV)")) {
std::istringstream iss2(line);
std::vector<std::string> results2((std::istream_iterator<std::string>(iss2)),
std::istream_iterator<std::string>());
Filename2_Obs = results2[0]; Filename2_Nav = results2[1];
object2.SetFilenames(Filename2_Obs.c_str(), Filename2_Nav.c_str());
}
if (strstr(line, "BASE FINAL COORDINATES")) {
string sline(line); // convert the line (char) to string class type sLine
string token = sline.substr(4, 56); // from 4th character upto 56
char cline[MAX_BYTE]; // cline is a char line
strncpy(cline, token.c_str(), sizeof(cline));
cline[sizeof(cline) - 1] = 0;
for (char * r = strtok(cline, " "); r; r = strtok(NULL, " "))
{
double rr = atof(r);
envi_records.base_final_coord.push_back(rr);
}
}
}
//......... Get a new line.......................
fgets(line, MAX_STRLEN, Env_File);
}
}
// This function computes the satellite positions and stores them in a global file
void SatellitePosition::Sat_Pos(SATPOS_struct &EPOCH_DATA)
{
RinexFile->rinexOBSReader(RinexFile->head, RinexFile->obs, RinexFile->SENTINEL); // Read the observation file
epoch_count = epoch_count + 1;
vector< vector<double> > pos_rot_epoch_temp;
vector< vector<double> > initial_satpos_temp;
vector <double> pr_epoch_temp;
vector <double> P1_epoch_temp;
vector <double> P2_epoch_temp;
vector <double> C1_epoch_temp;
vector <double> L1_epoch_temp;
vector <double> L2_epoch_temp;
vector <double> pr_epoch_Iono_temp;
vector <double> sat_offset_epoch_temp;
vector<double> sat_elev_temp;
double Tropo;
reader::NAVRECORDS storer;
if (RinexFile->obs.NumOfSat != 0) {
double count = 0;
for (int j = 0; j < RinexFile->obs.NumOfSat; j++) { // Each satellite
double gamma = pow((1575.42 / 1227.6), 2);
double c = 299792458;
double P1_temp = 0.0, P2_temp = 0.0, PR_temp = 0.0, L1_temp = 0.0, L2_temp = 0.0, C1_temp = 0.0, TIME_temp;
//reader::NAVRECORDS storer;
int curPrn = RinexFile->obs.prn[count]; // Current observation satelite vehicle
double time_LOGGER = std::numeric_limits<double>::max();
//search through the navigation file
for (size_t k = 0; k < RinexFile->SV_data.size(); k++) {
if (RinexFile->SV_data[k].PRN == curPrn) { //Compare obs prn with nav prn
if (time_LOGGER > abs(RinexFile->SV_data[k].gpstime - RinexFile->obs.time)) {
time_LOGGER = abs(RinexFile->SV_data[k].gpstime - RinexFile->obs.time);
storer = RinexFile->SV_data[k];
}
}
}
// Finding the pseudoranges P1 code
if (find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "P1") - RinexFile->head.obstype.begin() != RinexFile->head.nobstype) {
ptrdiff_t pos_P1 = find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "P1") - RinexFile->head.obstype.begin();
if (pos_P1 == RinexFile->head.obstype.size()) {
}
else {
P1_temp = RinexFile->obs.record[j][pos_P1];
}
}
// Finding the pseudoranges P2 code
if (find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "P1") - RinexFile->head.obstype.begin() != RinexFile->head.nobstype) {
ptrdiff_t pos_P2 = find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "P1") - RinexFile->head.obstype.begin();
if (pos_P2 == RinexFile->head.obstype.size()) {
}
else {
P2_temp = RinexFile->obs.record[j][pos_P2];
}
}
// Finding the pseudoranges L1 carrier
if (find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "L1") - RinexFile->head.obstype.begin() != RinexFile->head.nobstype) {
ptrdiff_t pos_L1 = find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "L1") - RinexFile->head.obstype.begin();
if (pos_L1 == RinexFile->head.obstype.size()) {
}
else {
L1_temp = RinexFile->obs.record[j][pos_L1];
}
}
// Finding the pseudoranges L2 carrier
if (find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "L2") - RinexFile->head.obstype.begin() != RinexFile->head.nobstype) {
ptrdiff_t pos_L2 = find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "L2") - RinexFile->head.obstype.begin();
if (pos_L2 == RinexFile->head.obstype.size()) {
}
else {
L2_temp = RinexFile->obs.record[j][pos_L2];
}
}
// Finding the pseudoranges C1 code
if (find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "C1") - RinexFile->head.obstype.begin() != RinexFile->head.nobstype) {
ptrdiff_t pos_C1 = find(RinexFile->head.obstype.begin(), RinexFile->head.obstype.end(), "C1") - RinexFile->head.obstype.begin();
if (pos_C1 == RinexFile->head.obstype.size()) {
}
else {
C1_temp = RinexFile->obs.record[j][pos_C1];
}
}
PR_temp = iono_free(j);
TIME_temp = RinexFile->obs.time - (PR_temp / c); //GPS system time at time of transmission corrected for transit time
// SATELLITE POSITIONING
// Constants
//WGS 84 value of the earth's gravitational constant for GPS user
double mu = 3.986005e14;
//WGS 84 value of the earth's rotation rate (rad/sec)
double OMEGA_e = 7.2921151467e-5;
// Initialize necessary variables from NAV
double A = pow(storer.Sqrta, 2); //Semi-major axis
double toe = storer.Toe; //toe = Time of Ephemeris
double deltaN = storer.DeltaN; //Delta n
double Mo = storer.Mo; // Mo angle
double e = storer.Eccentricity; //Orbit Eccentricity
double omega = storer.omega; //omega Angle
// Second Harmonic Perturbations
double Cus = storer.Cus; //Latitude Correction Sinus Component
double Cuc = storer.Cuc; //Latitude Correction Cosinus Component
double Crs = storer.Crs; //Radius Correction Sinus Component
double Crc = storer.Crc; //Radius Correction Cosinus Component
double Cis = storer.Cis; //Angular Velocity
double Cic = storer.Cic; //Inclination Correction Cosinus Component
double IDOT = storer.IDOT; //Inclination Rate
double Io = storer.Io; //Initial Inclination
double OMEGA = storer.OMEGA; //OMEGA Angle
double OMEGADOT = storer.OMEGADOT; //Angular Velocity
double SVCB = storer.SVClockBias; //SVClockBias (sec)
double SVCD = storer.SVClockDrift; //SVClockDrift (sec)
double SVCDR = storer.SVClockDriftRate; //SVClockDriftRate (sec)
double SAT_TIME = storer.gpstime;
//double SAT_TIME = storer.SEC;
double tk = TIME_temp - toe; //Time from ephemeris reference epoch
// Correct tk within range of -302400 to 302400
if (tk > 302400) {
tk = tk - 604800;
}
else if (tk < -302400) {
tk = tk + 604800;
}
// Computed mean motion (rad/sec)
double n0 = sqrt(mu / (pow(A, 3)));
// Corrected mean motion
double n = n0 + deltaN;
//Mean anomaly
double Mk = Mo + n*tk;
// Keep Mk with in 360 degrees ....// Mk = rem(Mk+2*pi,2*pi);
// Kepler's Equation for Eccentric Anomaly (may be solved by iteration)(radians)
double Ek = Mk;
double Ek0 = Mk + e*sin(Ek);
double limit = 1e-11; // limit
while (abs(Ek - Ek0) > limit) {
Ek0 = Ek;
Ek = Mk + e*sin(Ek0);
}
// Keep Ek with in 360 degrees.....// Ek = rem(Ek + 2 * pi, 2 * pi);
// True Anomaly
double Y = (sqrt(1 - pow(e, 2))*sin(Ek)) / (1 - e*cos(Ek));
double X = (cos(Ek) - e) / (1 - e*cos(Ek));
double vk = atan2(Y, X);
//Argument of Latitude
double Phi_k = vk + omega;
double del_uk = Cus*sin(2 * Phi_k) + Cuc*cos(2 * Phi_k); // Argument of Latitude Correction
double del_rk = Crs*sin(2 * Phi_k) + Crc*cos(2 * Phi_k); //Radius Correction
double del_ik = Cis*sin(2 * Phi_k) + Cic*cos(2 * Phi_k); //Inclination Correction
//Corrected Argument of Latitude
double uk = Phi_k + del_uk;
//Corrected Radius
double rk = A*(1 - e*cos(Ek)) + del_rk;
//Corrected Inclination
double ik = Io + del_ik + IDOT*tk;
//Positions in orbital plane.
double xk_prime = rk*cos(uk);
double yk_prime = rk*sin(uk);
//Corrected longitude of ascending node
double OMEGA_k = OMEGA + (OMEGADOT - OMEGA_e)*tk - OMEGA_e*toe;
//Earth-fixed coordinates
double xk = xk_prime*cos(OMEGA_k) - yk_prime*cos(ik)*sin(OMEGA_k);
double yk = xk_prime*sin(OMEGA_k) + yk_prime*cos(ik)*cos(OMEGA_k);
double zk = yk_prime*sin(ik);
// Satellite position without tropo, iono and Earth rotation corrections
vector <double> POSITION;
//Store the Earth-fixed coordinates (satellite position xk,yk,zk of satellite k)
POSITION.push_back(xk);
POSITION.push_back(yk);
POSITION.push_back(zk);
// Satellite elevation angle calculation
//--------------------------------------------------------------------------------------------------------------//
Eigen::Vector3d POS(POSITION[0], POSITION[1], POSITION[2]);
Eigen::Vector3d INI_POS(RinexFile->head.antpos[0], RinexFile->head.antpos[1], RinexFile->head.antpos[2]);
double R = 6371e3;
double sat_pos_norm = EucldNorm(POSITION[0], POSITION[1], POSITION[2]);
double rec_pos_norm = EucldNorm(RinexFile->head.antpos[0], RinexFile->head.antpos[1], RinexFile->head.antpos[2]);
double g = acos((POS.dot(INI_POS)) / (sat_pos_norm*rec_pos_norm));
double sat_elev = (atan((sat_pos_norm*cos(g) - R) / (sat_pos_norm*sin(g))))*(180 / PI); // in degrees
sat_elev_temp.push_back(sat_elev); // store the current satellite elevation
//----------------------------------------------------------------------------------------------------------------//
// CUT_OFF ANGLE OF 15 DEGREES
if (sat_elev >= 15) {
// Realativistic Correction Term (sec)
double F = -4.442807633e-10;
double Del_tr = F*e*sqrt(A)*sin(Ek); // Realativistic Correction Term(sec)
// Satellite Clock Errors (sec)
double Del_tsv = SVCB + SVCD*(SAT_TIME - toe) + SVCDR*(pow((SAT_TIME - toe), 2)) + Del_tr;
// CORRECTIONS
// Range before earth rotation correction
double geom_range = EucldNorm((POSITION[0] - RinexFile->head.antpos[0]), (POSITION[1] - RinexFile->head.antpos[1]), (POSITION[2] - RinexFile->head.antpos[2]));
double t = (geom_range) / c;
// CORRECTIONS
// Earth rotation correction
vector <double> POSITION_ROT = EarthRot_Corr(t, POSITION);
double geom_range_corr = EucldNorm((POSITION_ROT[0] - RinexFile->head.antpos[0]), (POSITION_ROT[1] - RinexFile->head.antpos[1]), (POSITION_ROT[2] - RinexFile->head.antpos[2]));
pos_rot_epoch_temp.push_back(POSITION_ROT);
double check_pseudo = (PR_temp - geom_range_corr) + c*(Del_tsv);
// Tropo correction
//double dtropo = NMF_hyd(sat_elev); // Niell Mapping Function
double dtropo = Tropo_Corr(POSITION_ROT, RinexFile->head.antpos); // SAASTAMOINEN
//Tropo = dtropo;
// Corrected pseudorange for iono only
pr_epoch_Iono_temp.push_back(PR_temp);
// Corrected pseudorange for iono and tropo
//double Corr_Pseudo = PR_temp - dtropo; doing tropo correc in kalman!!!!!
double Corr_Pseudo = PR_temp - dtropo;
pr_epoch_temp.push_back(Corr_Pseudo);
P1_epoch_temp.push_back(P1_temp);
P2_epoch_temp.push_back(P2_temp);
C1_epoch_temp.push_back(C1_temp);
L1_epoch_temp.push_back(L1_temp);
L2_epoch_temp.push_back(L2_temp);
sat_offset_epoch_temp.push_back(Del_tsv);
initial_satpos_temp.push_back(POSITION);
count = count + 1;
}
else {
//remove the satellite from the prn vector
count = count;
RinexFile->obs.prn.erase(RinexFile->obs.prn.begin() + count);
}
}
EPOCH_DATA.Sat_elev = sat_elev_temp; // Satellite elevations for the epoch
EPOCH_DATA.pos_rot_epoch = pos_rot_epoch_temp; // corrected satellite positions for the epoch
EPOCH_DATA.Initial_SatPos = initial_satpos_temp;
EPOCH_DATA.pr_epoch = pr_epoch_temp; // Corrected pseudorange
EPOCH_DATA.P1_epoch = P1_epoch_temp;
EPOCH_DATA.P2_epoch = P2_epoch_temp;
EPOCH_DATA.C1_epoch = C1_epoch_temp;
EPOCH_DATA.L1_epoch = L1_epoch_temp;
EPOCH_DATA.L2_epoch = L2_epoch_temp;
EPOCH_DATA.pr_epoch_iono = pr_epoch_Iono_temp;
EPOCH_DATA.sat_offset_epoch = sat_offset_epoch_temp; // satellite clock offset
}
}
讲解该代码
SV_Position在VS与PS中的应用解析
本文详细解析了SV_Position在顶点着色器(VS)与像素着色器(PS)中的作用与表现形式。在VS中，SV_Position用于写入裁剪空间位置；而在PS中，则读取屏幕像素位置与深度信息，揭示了其在不同阶段的数据转换与应用。
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