Hi All,
I am trying to write a modified TDOA class using Java and I am getting the error
no reference date set for parameter prime-meridian-offset
This is generated when executing the line,
final TimeStampedFieldPVCoordinates<Gradient> primePV =
primeToInert.transformPVCoordinates(new TimeStampedFieldPVCoordinates<>(measurementDateG,
zero, zero, zero));
I would some insight in to how to solve this issue.
I prefer not to use the syntax
final TimeStampedPVCoordinates primePV = primeStation.getBaseFrame().getPVCoordinates(mDate, state.getFrame());
to get the PV coordinates of the prime station. I tried this and getting slightly different values. Following is the first part of the class.
public class DiffOfArrivelPV extends AbstractMeasurement<DiffOfArrivelPV>{
//this class take satellite state, measurement date and calculate the
/*
* 1. primePV
* 2. satellitePV
* 3. secondPV
* 4. tau1
* 5. tau2
* 6. tdoa
*/
private TimeStampedFieldPVCoordinates<Gradient> primePV;
private TimeStampedFieldPVCoordinates<Gradient> secondPV;
private TimeStampedFieldPVCoordinates<Gradient> satellitePV;
private Gradient tau1;
private Gradient tau2;
private GroundStation primeStation;
private GroundStation secondStation;
private AbsoluteDate mDate;
public DiffOfArrivelPV(final GroundStation primeStation,final GroundStation secondStation,AbsoluteDate obDate,final ObservableSatellite satellite) {
super(obDate, 0.01, 0.01, 1.0, Collections.singletonList(satellite));
// add parameter drivers for the primary station
addParameterDriver(primeStation.getClockOffsetDriver());
addParameterDriver(primeStation.getClockDriftDriver());
addParameterDriver(primeStation.getEastOffsetDriver());
addParameterDriver(primeStation.getNorthOffsetDriver());
addParameterDriver(primeStation.getZenithOffsetDriver());
addParameterDriver(primeStation.getPrimeMeridianOffsetDriver());
addParameterDriver(primeStation.getPrimeMeridianDriftDriver());
addParameterDriver(primeStation.getPolarOffsetXDriver());
addParameterDriver(primeStation.getPolarDriftXDriver());
addParameterDriver(primeStation.getPolarOffsetYDriver());
addParameterDriver(primeStation.getPolarDriftYDriver());
// add parameter drivers for the secondary station
addParameterDriver(secondStation.getClockOffsetDriver());
addParameterDriver(secondStation.getClockDriftDriver());
addParameterDriver(secondStation.getEastOffsetDriver());
addParameterDriver(secondStation.getNorthOffsetDriver());
addParameterDriver(secondStation.getZenithOffsetDriver());
addParameterDriver(secondStation.getPrimeMeridianOffsetDriver());
addParameterDriver(secondStation.getPrimeMeridianDriftDriver());
addParameterDriver(secondStation.getPolarOffsetXDriver());
addParameterDriver(secondStation.getPolarDriftXDriver());
addParameterDriver(secondStation.getPolarOffsetYDriver());
addParameterDriver(secondStation.getPolarDriftYDriver());
// satellite
addParameterDriver(satellite.getClockDriftDriver());
this.primeStation = primeStation;
this.secondStation = secondStation;
this.mDate = obDate;
// Set parameters
}
public void calculatePVData(final SpacecraftState state) {
final double METERS_TO_KM = 1e-3;
int nbParams = 6;
final Map<String, Integer> indices = new HashMap<>();
final FieldVector3D<Gradient> zero = FieldVector3D.getZero(GradientField.getField(nbParams));
for (ParameterDriver driver : getParametersDrivers()) {
// we have to check for duplicate keys because primary and secondary station share
// pole and prime meridian parameters names that must be considered
// as one set only (they are combined together by the estimation engine)
if (driver.isSelected() && !indices.containsKey(driver.getName())) {
indices.put(driver.getName(), nbParams++);
}
}
// coordinates of the spacecraft as a gradient
final TimeStampedFieldPVCoordinates<Gradient> pvaG = AbstractMeasurement.getCoordinates(state, 0, nbParams);
// get the prime station iniertial frame as filedTransform
final FieldTransform<Gradient> primeToInert =
primeStation.getOffsetToInertial(state.getFrame(), mDate, nbParams, indices);
final FieldAbsoluteDate<Gradient> measurementDateG = primeToInert.getFieldDate();
// prime station PV in inertial frame at the real date of the measurement
final TimeStampedFieldPVCoordinates<Gradient> primePV =
primeToInert.transformPVCoordinates(new TimeStampedFieldPVCoordinates<>(measurementDateG,
zero, zero, zero));
// compute downlink delay from emitter to prime receiver
Gradient tau1 = AbstractMeasurement.signalTimeOfFlight(pvaG, primePV.getPosition(), measurementDateG);
// elapsed time between state date and signal arrival to the prime receiver
final Gradient dtMtau1 = measurementDateG.durationFrom(state.getDate()).subtract(tau1);
When I am using the above class with exiting TDOA class, the error does not appear . I am not sure how the reference date is set for primeMeridianDriftDriver by Orekit.
Thank you. !!
