OneWayGNSSPhase.java
- /* Copyright 2002-2023 CS GROUP
- * Licensed to CS GROUP (CS) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * CS licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- package org.orekit.estimation.measurements.gnss;
- import java.util.Arrays;
- import java.util.Collections;
- import java.util.HashMap;
- import java.util.Map;
- import org.hipparchus.analysis.differentiation.Gradient;
- import org.orekit.estimation.measurements.AbstractMeasurement;
- import org.orekit.estimation.measurements.EstimatedMeasurement;
- import org.orekit.estimation.measurements.EstimatedMeasurementBase;
- import org.orekit.estimation.measurements.ObservableSatellite;
- import org.orekit.propagation.SpacecraftState;
- import org.orekit.time.AbsoluteDate;
- import org.orekit.time.FieldAbsoluteDate;
- import org.orekit.utils.Constants;
- import org.orekit.utils.PVCoordinatesProvider;
- import org.orekit.utils.ParameterDriver;
- import org.orekit.utils.TimeSpanMap.Span;
- import org.orekit.utils.TimeStampedFieldPVCoordinates;
- import org.orekit.utils.TimeStampedPVCoordinates;
- /** One-way GNSS phase measurement.
- * <p>
- * This class can be used in precise orbit determination applications
- * for modeling a phase measurement between a GNSS satellite (emitter)
- * and a LEO satellite (receiver).
- * <p>
- * The one-way GNSS phase measurement assumes knowledge of the orbit and
- * the clock offset of the emitting GNSS satellite. For instance, it is
- * possible to use a SP3 file or a GNSS navigation message to recover
- * the satellite's orbit and clock.
- * <p>
- * This class is very similar to {@link InterSatellitesPhase} measurement
- * class. However, using the one-way GNSS phase measurement, the orbit and clock
- * of the emitting GNSS satellite are <b>NOT</b> estimated simultaneously with
- * LEO satellite coordinates.
- *
- * @author Bryan Cazabonne
- * @since 10.3
- */
- public class OneWayGNSSPhase extends AbstractMeasurement<OneWayGNSSPhase> {
- /** Type of the measurement. */
- public static final String MEASUREMENT_TYPE = "OneWayGNSSPhase";
- /** Name for ambiguity driver. */
- public static final String AMBIGUITY_NAME = "ambiguity";
- /** Driver for ambiguity. */
- private final ParameterDriver ambiguityDriver;
- /** Emitting satellite. */
- private final PVCoordinatesProvider remote;
- /** Clock offset of the emitting satellite. */
- private final double dtRemote;
- /** Wavelength of the phase observed value [m]. */
- private final double wavelength;
- /** Simple constructor.
- * @param remote provider for GNSS satellite which simply emits the signal
- * @param dtRemote clock offset of the GNSS satellite, in seconds
- * @param date date of the measurement
- * @param phase observed value, in cycles
- * @param wavelength phase observed value wavelength, in meters
- * @param sigma theoretical standard deviation
- * @param baseWeight base weight
- * @param local satellite which receives the signal and perform the measurement
- */
- public OneWayGNSSPhase(final PVCoordinatesProvider remote,
- final double dtRemote,
- final AbsoluteDate date,
- final double phase, final double wavelength, final double sigma,
- final double baseWeight, final ObservableSatellite local) {
- // Call super constructor
- super(date, phase, sigma, baseWeight, Collections.singletonList(local));
- // Initialize phase ambiguity driver
- ambiguityDriver = new ParameterDriver(AMBIGUITY_NAME, 0.0, 1.0,
- Double.NEGATIVE_INFINITY, Double.POSITIVE_INFINITY);
- // The local satellite clock offset affects the measurement
- addParameterDriver(ambiguityDriver);
- addParameterDriver(local.getClockOffsetDriver());
- // Initialise fields
- this.dtRemote = dtRemote;
- this.remote = remote;
- this.wavelength = wavelength;
- }
- /** Get the wavelength.
- * @return wavelength (m)
- */
- public double getWavelength() {
- return wavelength;
- }
- /** Get the driver for phase ambiguity.
- * @return the driver for phase ambiguity
- */
- public ParameterDriver getAmbiguityDriver() {
- return ambiguityDriver;
- }
- /** {@inheritDoc} */
- @Override
- protected EstimatedMeasurementBase<OneWayGNSSPhase> theoreticalEvaluationWithoutDerivatives(final int iteration,
- final int evaluation,
- final SpacecraftState[] states) {
- // Coordinates of both satellites
- final SpacecraftState localState = states[0];
- final TimeStampedPVCoordinates pvaLocal = localState.getPVCoordinates();
- final TimeStampedPVCoordinates pvaRemote = remote.getPVCoordinates(getDate(), localState.getFrame());
- // Downlink delay
- final double dtLocal = getSatellites().get(0).getClockOffsetDriver().getValue(localState.getDate());
- final AbsoluteDate arrivalDate = getDate().shiftedBy(-dtLocal);
- final TimeStampedPVCoordinates s1Downlink =
- pvaLocal.shiftedBy(arrivalDate.durationFrom(pvaLocal.getDate()));
- final double tauD = signalTimeOfFlight(pvaRemote, s1Downlink.getPosition(), arrivalDate);
- // Transit state
- final double delta = getDate().durationFrom(pvaRemote.getDate());
- final double deltaMTauD = delta - tauD;
- // prepare the evaluation
- final EstimatedMeasurementBase<OneWayGNSSPhase> estimatedPhase =
- new EstimatedMeasurementBase<>(this, iteration, evaluation,
- new SpacecraftState[] {
- localState.shiftedBy(deltaMTauD)
- }, new TimeStampedPVCoordinates[] {
- pvaRemote.shiftedBy(delta - tauD),
- localState.shiftedBy(delta).getPVCoordinates()
- });
- // Phase value
- final double cOverLambda = Constants.SPEED_OF_LIGHT / wavelength;
- final double ambiguity = ambiguityDriver.getValue(localState.getDate());
- final double phase = (tauD + dtLocal - dtRemote) * cOverLambda + ambiguity;
- // Set value of the estimated measurement
- estimatedPhase.setEstimatedValue(phase);
- // Return the estimated measurement
- return estimatedPhase;
- }
- /** {@inheritDoc} */
- @Override
- protected EstimatedMeasurement<OneWayGNSSPhase> theoreticalEvaluation(final int iteration,
- final int evaluation,
- final SpacecraftState[] states) {
- // Phase derivatives are computed with respect to spacecrafts states in inertial frame
- // Parameters:
- // - 0..2 - Position of the receiver satellite in inertial frame
- // - 3..5 - Velocity of the receiver satellite in inertial frame
- // - 6..n - Measurement parameters: ambiguity and clock offset
- int nbEstimatedParamsPhase = 6;
- final Map<String, Integer> parameterIndicesPhase = new HashMap<>();
- for (ParameterDriver phaseMeasurementDriver : getParametersDrivers()) {
- if (phaseMeasurementDriver.isSelected()) {
- for (Span<String> span = phaseMeasurementDriver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
- parameterIndicesPhase.put(span.getData(), nbEstimatedParamsPhase++);
- }
- }
- }
- // Coordinates of both satellites
- final SpacecraftState localState = states[0];
- final TimeStampedFieldPVCoordinates<Gradient> pvaLocal = getCoordinates(localState, 0, nbEstimatedParamsPhase);
- final TimeStampedPVCoordinates pvaRemote = remote.getPVCoordinates(getDate(), localState.getFrame());
- // Downlink delay
- final Gradient dtLocal = getSatellites().get(0).getClockOffsetDriver().getValue(nbEstimatedParamsPhase, parameterIndicesPhase, localState.getDate());
- final FieldAbsoluteDate<Gradient> arrivalDate = new FieldAbsoluteDate<>(getDate(), dtLocal.negate());
- final TimeStampedFieldPVCoordinates<Gradient> s1Downlink =
- pvaLocal.shiftedBy(arrivalDate.durationFrom(pvaLocal.getDate()));
- final Gradient tauD = signalTimeOfFlight(new TimeStampedFieldPVCoordinates<>(pvaRemote.getDate(), dtLocal.getField().getOne(), pvaRemote),
- s1Downlink.getPosition(), arrivalDate);
- // Transit state
- final double delta = getDate().durationFrom(pvaRemote.getDate());
- final Gradient deltaMTauD = tauD.negate().add(delta);
- // prepare the evaluation
- final EstimatedMeasurement<OneWayGNSSPhase> estimatedPhase =
- new EstimatedMeasurement<>(this, iteration, evaluation,
- new SpacecraftState[] {
- localState.shiftedBy(deltaMTauD.getValue())
- }, new TimeStampedPVCoordinates[] {
- pvaRemote.shiftedBy(delta - tauD.getValue()),
- localState.shiftedBy(delta).getPVCoordinates()
- });
- // Phase value
- final double cOverLambda = Constants.SPEED_OF_LIGHT / wavelength;
- final Gradient ambiguity = ambiguityDriver.getValue(nbEstimatedParamsPhase, parameterIndicesPhase, localState.getDate());
- final Gradient phase = tauD.add(dtLocal).subtract(dtRemote).multiply(cOverLambda).add(ambiguity);
- final double[] phaseDerivatives = phase.getGradient();
- // Set value and state derivatives of the estimated measurement
- estimatedPhase.setEstimatedValue(phase.getValue());
- estimatedPhase.setStateDerivatives(0, Arrays.copyOfRange(phaseDerivatives, 0, 6));
- // Set partial derivatives with respect to parameters
- for (final ParameterDriver phaseMeasurementDriver : getParametersDrivers()) {
- for (Span<String> span = phaseMeasurementDriver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
- final Integer index = parameterIndicesPhase.get(span.getData());
- if (index != null) {
- estimatedPhase.setParameterDerivatives(phaseMeasurementDriver, span.getStart(), phaseDerivatives[index]);
- }
- }
- }
- // Return the estimated measurement
- return estimatedPhase;
- }
- }