AbstractOneWayGNSSMeasurement.java
/* Copyright 2002-2024 Luc Maisonobe
* 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.Collections;
import org.hipparchus.analysis.differentiation.Gradient;
import org.orekit.estimation.measurements.ObservableSatellite;
import org.orekit.estimation.measurements.ObservedMeasurement;
import org.orekit.estimation.measurements.QuadraticClockModel;
import org.orekit.propagation.SpacecraftState;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.FieldPVCoordinatesProvider;
import org.orekit.utils.PVCoordinatesProvider;
import org.orekit.utils.TimeStampedFieldPVCoordinates;
import org.orekit.utils.TimeStampedPVCoordinates;
/** Base class for one-way GNSS measurement.
* <p>
* This class can be used in precise orbit determination applications
* for modeling a range measurement between a GNSS satellite (emitter)
* and a LEO satellite (receiver).
* </p>
* <p>
* The one-way GNSS range 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>
* <p>
* This class is very similar to {@link AbstractInterSatellitesMeasurement} measurement
* class. However, using the one-way GNSS range measurement, the orbit and clock
* of the emitting GNSS satellite are <b>NOT</b> estimated simultaneously with
* LEO satellite coordinates.
* </p>
*
* @param <T> type of the measurement
* @author Luc Maisonobe
* @since 12.1
*/
public abstract class AbstractOneWayGNSSMeasurement<T extends ObservedMeasurement<T>>
extends AbstractOnBoardMeasurement<T> {
/** Emitting satellite. */
private final PVCoordinatesProvider remotePV;
/** Clock offset of the emitting satellite. */
private final QuadraticClockModel remoteClock;
/** Simple constructor.
* @param remotePV provider for GNSS satellite which simply emits the signal
* @param remoteClock clock offset of the GNSS satellite
* @param date date of the measurement
* @param range observed value
* @param sigma theoretical standard deviation
* @param baseWeight base weight
* @param local satellite which receives the signal and perform the measurement
*/
public AbstractOneWayGNSSMeasurement(final PVCoordinatesProvider remotePV,
final QuadraticClockModel remoteClock,
final AbsoluteDate date,
final double range, final double sigma,
final double baseWeight, final ObservableSatellite local) {
// Call super constructor
super(date, range, sigma, baseWeight, Collections.singletonList(local));
// The local satellite clock offset affects the measurement
addParameterDriver(local.getClockOffsetDriver());
addParameterDriver(local.getClockDriftDriver());
addParameterDriver(local.getClockAccelerationDriver());
// Initialise fields
this.remotePV = remotePV;
this.remoteClock = remoteClock;
}
/** {@inheritDoc} */
@Override
protected PVCoordinatesProvider getRemotePV(final SpacecraftState[] states) {
return remotePV;
}
/** {@inheritDoc} */
@Override
protected QuadraticClockModel getRemoteClock() {
return remoteClock;
}
/** {@inheritDoc} */
@Override
protected FieldPVCoordinatesProvider<Gradient> getRemotePV(final SpacecraftState[] states,
final int freeParameters) {
// convert the PVCoordinatesProvider to a FieldPVCoordinatesProvider<Gradient>
return (date, frame) -> {
// apply the raw (no derivatives) remote provider
final AbsoluteDate dateBase = date.toAbsoluteDate();
final TimeStampedPVCoordinates pvBase = remotePV.getPVCoordinates(dateBase, frame);
final TimeStampedFieldPVCoordinates<Gradient> pvWithoutDerivatives =
new TimeStampedFieldPVCoordinates<>(date.getField(), pvBase);
// add derivatives, using a trick: we shift the date by 0, with derivatives
final Gradient zeroWithDerivatives = date.durationFrom(dateBase);
return pvWithoutDerivatives.shiftedBy(zeroWithDerivatives);
};
}
}