OneWayGNSSRange.java

  1. /* Copyright 2002-2025 CS GROUP
  2.  * Licensed to CS GROUP (CS) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * CS licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *   http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  17. package org.orekit.estimation.measurements.gnss;

  19. import java.util.Arrays;

  21. import org.hipparchus.analysis.differentiation.Gradient;
  22. import org.orekit.estimation.measurements.EstimatedMeasurement;
  23. import org.orekit.estimation.measurements.EstimatedMeasurementBase;
  24. import org.orekit.estimation.measurements.InterSatellitesRange;
  25. import org.orekit.estimation.measurements.ObservableSatellite;
  26. import org.orekit.estimation.measurements.QuadraticClockModel;
  27. import org.orekit.propagation.SpacecraftState;
  28. import org.orekit.time.AbsoluteDate;
  29. import org.orekit.utils.Constants;
  30. import org.orekit.utils.PVCoordinatesProvider;
  31. import org.orekit.utils.ParameterDriver;
  32. import org.orekit.utils.TimeSpanMap.Span;
  33. import org.orekit.utils.TimeStampedPVCoordinates;

  35. /** One-way GNSS range measurement.
  36.  * <p>
  37.  * This class can be used in precise orbit determination applications
  38.  * for modeling a range measurement between a GNSS satellite (emitter)
  39.  * and a LEO satellite (receiver).
  40.  * <p>
  41.  * The one-way GNSS range measurement assumes knowledge of the orbit and
  42.  * the clock offset of the emitting GNSS satellite. For instance, it is
  43.  * possible to use a SP3 file or a GNSS navigation message to recover
  44.  * the satellite's orbit and clock.
  45.  * <p>
  46.  * This class is very similar to {@link InterSatellitesRange} measurement
  47.  * class. However, using the one-way GNSS range measurement, the orbit and clock
  48.  * of the emitting GNSS satellite are <b>NOT</b> estimated simultaneously with
  49.  * LEO satellite coordinates.
  50.  *
  51.  * @author Bryan Cazabonne
  52.  * @since 10.3
  53.  */
  54. public class OneWayGNSSRange extends AbstractOneWayGNSSMeasurement<OneWayGNSSRange> {

  56.     /** Type of the measurement. */
  57.     public static final String MEASUREMENT_TYPE = "OneWayGNSSRange";

  59.     /** Simple constructor.
  60.      * @param remote provider for GNSS satellite which simply emits the signal
  61.      * @param dtRemote clock offset of the GNSS satellite, in seconds
  62.      * @param date date of the measurement
  63.      * @param range observed value
  64.      * @param sigma theoretical standard deviation
  65.      * @param baseWeight base weight
  66.      * @param local satellite which receives the signal and perform the measurement
  67.      */
  68.     public OneWayGNSSRange(final PVCoordinatesProvider remote,
  69.                            final double dtRemote,
  70.                            final AbsoluteDate date,
  71.                            final double range, final double sigma,
  72.                            final double baseWeight, final ObservableSatellite local) {
  73.         this(remote, new QuadraticClockModel(date, dtRemote, 0.0, 0.0), date, range, sigma, baseWeight, local);
  74.     }

  76.     /** Simple constructor.
  77.      * @param remote provider for GNSS satellite which simply emits the signal
  78.      * @param remoteClock clock offset of the GNSS satellite
  79.      * @param date date of the measurement
  80.      * @param range observed value
  81.      * @param sigma theoretical standard deviation
  82.      * @param baseWeight base weight
  83.      * @param local satellite which receives the signal and perform the measurement
  84.      * @since 12.1
  85.      */
  86.     public OneWayGNSSRange(final PVCoordinatesProvider remote,
  87.                            final QuadraticClockModel remoteClock,
  88.                            final AbsoluteDate date,
  89.                            final double range, final double sigma,
  90.                            final double baseWeight, final ObservableSatellite local) {
  91.         // Call super constructor
  92.         super(remote, remoteClock, date, range, sigma, baseWeight, local);
  93.     }

  95.     /** {@inheritDoc} */
  96.     @Override
  97.     protected EstimatedMeasurementBase<OneWayGNSSRange> theoreticalEvaluationWithoutDerivatives(final int iteration,
  98.                                                                                                 final int evaluation,
  99.                                                                                                 final SpacecraftState[] states) {


  102.         final OnBoardCommonParametersWithoutDerivatives common = computeCommonParametersWithout(states, false);

  104.         // Estimated measurement
  105.         final EstimatedMeasurementBase<OneWayGNSSRange> estimatedRange =
  106.                         new EstimatedMeasurementBase<>(this, iteration, evaluation,
  107.                                                        new SpacecraftState[] {
  108.                                                            common.getState()
  109.                                                        }, new TimeStampedPVCoordinates[] {
  110.                                                            common.getRemotePV(),
  111.                                                            common.getTransitPV()
  112.                                                        });

  114.         // Range value
  115.         final double range = (common.getTauD() + common.getLocalOffset() - common.getRemoteOffset()) *
  116.                              Constants.SPEED_OF_LIGHT;

  118.         // Set value of the estimated measurement
  119.         estimatedRange.setEstimatedValue(range);

  121.         // Return the estimated measurement
  122.         return estimatedRange;

  124.     }

  126.     /** {@inheritDoc} */
  127.     @Override
  128.     protected EstimatedMeasurement<OneWayGNSSRange> theoreticalEvaluation(final int iteration,
  129.                                                                           final int evaluation,
  130.                                                                           final SpacecraftState[] states) {

  132.         final OnBoardCommonParametersWithDerivatives common = computeCommonParametersWith(states, false);

  134.         // Estimated measurement
  135.         final EstimatedMeasurement<OneWayGNSSRange> estimatedRange =
  136.                         new EstimatedMeasurement<>(this, iteration, evaluation,
  137.                                                    new SpacecraftState[] {
  138.                                                        common.getState()
  139.                                                    }, new TimeStampedPVCoordinates[] {
  140.                                                        common.getRemotePV().toTimeStampedPVCoordinates(),
  141.                                                        common.getTransitPV().toTimeStampedPVCoordinates()
  142.                                                    });

  144.         // Range value
  145.         final Gradient range            = common.getTauD().add(common.getLocalOffset()).subtract(common.getRemoteOffset()).
  146.                                           multiply(Constants.SPEED_OF_LIGHT);
  147.         final double[] rangeDerivatives = range.getGradient();

  149.         // Set value and state first order derivatives of the estimated measurement
  150.         estimatedRange.setEstimatedValue(range.getValue());
  151.         estimatedRange.setStateDerivatives(0, Arrays.copyOfRange(rangeDerivatives, 0,  6));

  153.         // Set first order derivatives with respect to parameters
  154.         for (final ParameterDriver measurementDriver : getParametersDrivers()) {
  155.             for (Span<String> span = measurementDriver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {

  157.                 final Integer index = common.getIndices().get(span.getData());
  158.                 if (index != null) {
  159.                     estimatedRange.setParameterDerivatives(measurementDriver, span.getStart(), rangeDerivatives[index]);
  160.                 }
  161.             }
  162.         }

  164.         // Return the estimated measurement
  165.         return estimatedRange;

  167.     }

  169. }
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