public GpsConstellation()
{
// URL template from where the GPS ephemerides should be downloaded
string IGN_NAVIGATION_HOURLY_ZIM2 = "ftp://igs.ensg.ign.fr/pub/igs/data/hourly/${yyyy}/${ddd}/zim2${ddd}${h}.${yy}n.Z";
string NASA_NAVIGATION_HOURLY = "ftp://cddis.gsfc.nasa.gov/pub/gps/data/hourly/${yyyy}/${ddd}/hour${ddd}0.${yy}n.Z";
string GARNER_NAVIGATION_AUTO_HTTP = "http://garner.ucsd.edu/pub/rinex/${yyyy}/${ddd}/auto${ddd}0.${yy}n.Z";
string BKG_HOURLY_SUPER_SEVER = "ftp://igs.bkg.bund.de/IGS/BRDC/${yyyy}/${ddd}/brdc${ddd}0.${yy}n.Z";
// Declare a RinexNavigation type object
if (rinexNavGps == null)
{
var rn = new RinexNavigationGps(BKG_HOURLY_SUPER_SEVER);
rinexNavGps = rn;
}
}
public override void calculateCorrection(Time currentTime, Coordinates <Matrix> approximatedPose, SatellitePosition satelliteCoordinates, NavigationProducer navigationProducer, Location initialLocation)
{
DateTime foo = DateTime.Now;
long unixTime = ((DateTimeOffset)foo).ToUnixTimeSeconds();
IonoGps iono = navigationProducer.getIono(unixTime, initialLocation);
if (iono.getBeta(0) == 0)
{
correctionValue = 0.0;
}
else
{
// Compute the elevation and azimuth angles for each satellite
TopocentricCoordinates <Matrix> topo = new TopocentricCoordinates <Matrix>();
topo.computeTopocentric(approximatedPose, satelliteCoordinates);
// Assign the elevation and azimuth information to new variables
double elevation = topo.getElevation();
double azimuth = topo.getAzimuth();
double ionoCorr = 0;
if (iono == null)
{
return;
}
// double a0 = navigation.getIono(currentTime.getMsec(),0);
// double a1 = navigation.getIono(currentTime.getMsec(),1);
// double a2 = navigation.getIono(currentTime.getMsec(),2);
// double a3 = navigation.getIono(currentTime.getMsec(),3);
// double b0 = navigation.getIono(currentTime.getMsec(),4);
// double b1 = navigation.getIono(currentTime.getMsec(),5);
// double b2 = navigation.getIono(currentTime.getMsec(),6);
// double b3 = navigation.getIono(currentTime.getMsec(),7);
elevation = Math.Abs(elevation);
// Parameter conversion to semicircles
double lon = approximatedPose.getGeodeticLongitude() / 180; // geod.get(0)
double lat = approximatedPose.getGeodeticLatitude() / 180; //geod.get(1)
azimuth = azimuth / 180;
elevation = elevation / 180;
// Klobuchar algorithm
// Compute the slant factor
double f = 1 + 16 * Math.Pow((0.53 - elevation), 3);
// Compute the earth-centred angle
double psi = 0.0137 / (elevation + 0.11) - 0.022;
// Compute the latitude of the Ionospheric Pierce Point (IPP)
double phi = lat + psi * Math.Cos(azimuth * Math.PI);
if (phi > 0.416)
{
phi = 0.416;
}
if (phi < -0.416)
{
phi = -0.416;
}
// Compute the longitude of the IPP
double lambda = lon + (psi * Math.Sin(azimuth * Math.PI))
/ Math.Cos(phi * Math.PI);
// Find the geomagnetic latitude of the IPP
double ro = phi + 0.064 * Math.Cos((lambda - 1.617) * Math.PI);
// Find the local time at the IPP
double t = lambda * 43200 + unixTime;
while (t >= 86400)
{
t = t - 86400;
}
while (t < 0)
{
t = t + 86400;
}
// Compute the period of ionospheric delay
double p = iono.getBeta(0) + iono.getBeta(1) * ro + iono.getBeta(2) * Math.Pow(ro, 2) + iono.getBeta(3) * Math.Pow(ro, 3);
if (p < 72000)
{
p = 72000;
}
// Compute the amplitude of ionospheric delay
double a = iono.getAlpha(0) + iono.getAlpha(1) * ro + iono.getAlpha(2) * Math.Pow(ro, 2) + iono.getAlpha(3) * Math.Pow(ro, 3);
if (a < 0)
{
a = 0;
}
// Compute the phase of ionospheric delay
double x = (2 * Math.PI * (t - 50400)) / p;
// Compute the ionospheric correction
if (Math.Abs(x) < 1.57)
{
ionoCorr = Constants.SPEED_OF_LIGHT
* f
* (5e-9 + a
* (1 - (Math.Pow(x, 2)) / 2 + (Math.Pow(x, 4)) / 24));
}
else
{
ionoCorr = Constants.SPEED_OF_LIGHT * f * 5e-9;
}
correctionValue = ionoCorr;
}
}
public override void calculateCorrection(Time currentTime, Coordinates <Matrix> approximatedPose, SatellitePosition satelliteCoordinates, NavigationProducer navigationProducer, Location initialLocation)
{
// Compute the difference vector between the receiver and the satellite
SimpleMatrix <Matrix> diff = approximatedPose.minusXYZ(satelliteCoordinates);
// Compute the geometric distance between the receiver and the satellite
double geomDist = Math.Sqrt(Math.Pow(diff.get(0), 2) + Math.Pow(diff.get(1), 2) + Math.Pow(diff.get(2), 2));
// Compute the geocentric distance of the receiver
double geoDistRx = Math.Sqrt(Math.Pow(approximatedPose.getX(), 2) + Math.Pow(approximatedPose.getY(), 2) + Math.Pow(approximatedPose.getZ(), 2));
// Compute the geocentric distance of the satellite
double geoDistSv = Math.Sqrt(Math.Pow(satelliteCoordinates.getX(), 2) + Math.Pow(satelliteCoordinates.getY(), 2) + Math.Pow(satelliteCoordinates.getZ(), 2));
// Compute the shapiro correction
correctionValue = ((2.0 * Constants.EARTH_GRAVITATIONAL_CONSTANT) / Math.Pow(Constants.SPEED_OF_LIGHT, 2)) * Math.Log((geoDistSv + geoDistRx + geomDist) / (geoDistSv + geoDistRx - geomDist));
}
public override void calculateCorrection(Time currentTime, Coordinates <Matrix> approximatedPose, SatellitePosition satelliteCoordinates, NavigationProducer navigationProducer, Location initialLocation)
{
// Compute also the geodetic version of the user position (latitude, longitude, height)
approximatedPose.computeGeodetic();
// Get the user's height
double height = approximatedPose.getGeodeticHeight();
// Compute the elevation and azimuth angles for each satellite
TopocentricCoordinates <Matrix> topo = new TopocentricCoordinates <Matrix>();
topo.computeTopocentric(approximatedPose, satelliteCoordinates);
// Assign the elevation information to a new variable
double elevation = topo.getElevation();
double tropoCorr = 0;
if (height > 5000)
{
return;
}
elevation = Math.Abs(elevation) / 180.0 * Math.PI;
if (elevation == 0)
{
elevation = elevation + 0.01;
}
// Numerical constants and tables for Saastamoinen algorithm
// (troposphere correction)
double hr = 50.0;
int[] ha = { 0, 500, 1000, 1500, 2000, 2500, 3000, 4000, 5000 };
double[] ba = { 1.156, 1.079, 1.006, 0.938, 0.874, 0.813, 0.757, 0.654, 0.563 };
// Saastamoinen algorithm
double P = Constants.STANDARD_PRESSURE * Math.Pow((1 - 0.0000226 * height), 5.225);
double T = Constants.STANDARD_TEMPERATURE - 0.0065 * height;
double H = hr * Math.Exp(-0.0006396 * height);
// If height is below zero, keep the maximum correction value
double B = ba[0];
// Otherwise, interpolate the tables
if (height >= 0)
{
int i = 1;
while (height > ha[i])
{
i++;
}
double m = (ba[i] - ba[i - 1]) / (ha[i] - ha[i - 1]);
B = ba[i - 1] + m * (height - ha[i - 1]);
}
double e = 0.01
* H
* Math.Exp(-37.2465 + 0.213166 * T - 0.000256908
* Math.Pow(T, 2));
tropoCorr = ((0.002277 / Math.Sin(elevation))
* (P - (B / Math.Pow(Math.Tan(elevation), 2))) + (0.002277 / Math.Sin(elevation))
* (1255 / T + 0.05) * e);
correctionValue = tropoCorr;
}
/**
* Calculates current correction for given parameters
* @param currentTime current timestamp
* @param approximatedPose approximate pose of the receiver
* @param satelliteCoordinates satellite coordinates
* @param navigationProducer Klobuchar coefficients from the naivgation message (ephemeris)
* @return calculated correction to be applied to the pseudorange
*/
public abstract void calculateCorrection(
Time currentTime,
Coordinates <Matrix> approximatedPose,
SatellitePosition satelliteCoordinates,
NavigationProducer navigationProducer,
Location initialLocation);
