PhaseTroposphericDelayModifier.java

  1. /* Copyright 2002-2024 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.  * The ASF 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.modifiers;

  19. import java.util.Arrays;
  20. import java.util.List;

  22. import org.hipparchus.CalculusFieldElement;
  23. import org.hipparchus.Field;
  24. import org.hipparchus.analysis.differentiation.Gradient;
  25. import org.orekit.attitudes.FrameAlignedProvider;
  26. import org.orekit.estimation.measurements.EstimatedMeasurement;
  27. import org.orekit.estimation.measurements.EstimatedMeasurementBase;
  28. import org.orekit.estimation.measurements.EstimationModifier;
  29. import org.orekit.estimation.measurements.GroundStation;
  30. import org.orekit.estimation.measurements.gnss.Phase;
  31. import org.orekit.models.earth.troposphere.TroposphericModel;
  32. import org.orekit.propagation.FieldSpacecraftState;
  33. import org.orekit.propagation.SpacecraftState;
  34. import org.orekit.utils.Differentiation;
  35. import org.orekit.utils.FieldTrackingCoordinates;
  36. import org.orekit.utils.ParameterDriver;
  37. import org.orekit.utils.ParameterFunction;
  38. import org.orekit.utils.TimeSpanMap.Span;
  39. import org.orekit.utils.TrackingCoordinates;

  41. /**
  42.  * Class modifying theoretical phase measurement with tropospheric delay.
  43.  * The effect of tropospheric correction on the phase is directly computed
  44.  * through the computation of the tropospheric delay.
  45.  * @author David Soulard
  46.  * @author Bryan Cazabonne
  47.  * @since 10.2
  48.  */
  49. public class PhaseTroposphericDelayModifier implements EstimationModifier<Phase> {

  51.     /** Tropospheric delay model. */
  52.     private final TroposphericModel tropoModel;

  54.     /** Constructor.
  55.      *
  56.      * @param model  Tropospheric delay model appropriate for the current range measurement method.
  57.      * @deprecated as of 12.1, replaced by {@link #PhaseTroposphericDelayModifier(TroposphericModel)}
  58.      */
  59.     @Deprecated
  60.     public PhaseTroposphericDelayModifier(final org.orekit.models.earth.troposphere.DiscreteTroposphericModel model) {
  61.         this(new org.orekit.models.earth.troposphere.TroposphericModelAdapter(model));
  62.     }

  64.     /** Constructor.
  65.      *
  66.      * @param model  Tropospheric delay model appropriate for the current range measurement method.
  67.      * @since 12.1
  68.      */
  69.     public PhaseTroposphericDelayModifier(final TroposphericModel model) {
  70.         tropoModel = model;
  71.     }

  73.     /** Compute the measurement error due to Troposphere.
  74.      * @param station station
  75.      * @param state spacecraft state
  76.      * @param wavelength wavelength of the signal
  77.      * @return the measurement error due to Troposphere
  78.      */
  79.     private double phaseErrorTroposphericModel(final GroundStation station, final SpacecraftState state, final double wavelength) {

  81.         // tracking
  82.         final TrackingCoordinates trackingCoordinates =
  83.                         station.getBaseFrame().getTrackingCoordinates(state.getPosition(), state.getFrame(), state.getDate());

  85.         // only consider measures above the horizon
  86.         if (trackingCoordinates.getElevation() > 0) {
  87.             // delay in meters
  88.             final double delay = tropoModel.pathDelay(trackingCoordinates,
  89.                                                       station.getOffsetGeodeticPoint(state.getDate()),
  90.                                                       station.getPressureTemperatureHumidity(state.getDate()),
  91.                                                       tropoModel.getParameters(state.getDate()), state.getDate()).
  92.                                  getDelay();

  94.             return delay / wavelength;
  95.         }

  97.         return 0;
  98.     }

  100.     /** Compute the measurement error due to Troposphere.
  101.      * @param <T> type of the element
  102.      * @param station station
  103.      * @param state spacecraft state
  104.      * @param parameters tropospheric model parameters
  105.      * @param wavelength of the measurements
  106.      * @return the measurement error due to Troposphere
  107.      */
  108.     private <T extends CalculusFieldElement<T>> T phaseErrorTroposphericModel(final GroundStation station,
  109.                                                                           final FieldSpacecraftState<T> state,
  110.                                                                           final T[] parameters, final double wavelength) {

  112.         // Field
  113.         final Field<T> field = state.getDate().getField();
  114.         final T zero         = field.getZero();

  116.         // tracking
  117.         final FieldTrackingCoordinates<T> trackingCoordinates =
  118.                         station.getBaseFrame().getTrackingCoordinates(state.getPosition(), state.getFrame(), state.getDate());


  121.         // only consider measures above the horizon
  122.         if (trackingCoordinates.getElevation().getReal() > 0) {
  123.             // delay in meters
  124.             final T delay = tropoModel.pathDelay(trackingCoordinates,
  125.                                                  station.getOffsetGeodeticPoint(state.getDate()),
  126.                                                  station.getPressureTemperatureHumidity(state.getDate()),
  127.                                                  parameters, state.getDate()).
  128.                             getDelay();

  130.             return delay.divide(wavelength);
  131.         }

  133.         return zero;
  134.     }

  136.     /** Compute the Jacobian of the delay term wrt state using
  137.     * automatic differentiation.
  138.     *
  139.     * @param derivatives tropospheric delay derivatives
  140.     *
  141.     * @return Jacobian of the delay wrt state
  142.     */
  143.     private double[][] phaseErrorJacobianState(final double[] derivatives) {
  144.         final double[][] finiteDifferencesJacobian = new double[1][6];
  145.         System.arraycopy(derivatives, 0, finiteDifferencesJacobian[0], 0, 6);
  146.         return finiteDifferencesJacobian;
  147.     }

  149.     /** Compute the derivative of the delay term wrt parameters.
  150.      *
  151.      * @param station ground station
  152.      * @param driver driver for the station offset parameter
  153.      * @param state spacecraft state
  154.      * @param wavelength wavelength of the signal
  155.      * @return derivative of the delay wrt station offset parameter
  156.      */
  157.     private double phaseErrorParameterDerivative(final GroundStation station,
  158.                                                  final ParameterDriver driver,
  159.                                                  final SpacecraftState state,
  160.                                                  final double wavelength) {
  161.         final ParameterFunction rangeError = (parameterDriver, date) -> phaseErrorTroposphericModel(station, state, wavelength);
  162.         final ParameterFunction phaseErrorDerivative =
  163.                         Differentiation.differentiate(rangeError, 3, 10.0 * driver.getScale());
  164.         return phaseErrorDerivative.value(driver, state.getDate());

  166.     }

  168.     /** Compute the derivative of the delay term wrt parameters using
  169.     * automatic differentiation.
  170.     *
  171.     * @param derivatives tropospheric delay derivatives
  172.     * @param freeStateParameters dimension of the state.
  173.     * @return derivative of the delay wrt tropospheric model parameters
  174.     */
  175.     private double[] phaseErrorParameterDerivative(final double[] derivatives, final int freeStateParameters) {
  176.         // 0 ... freeStateParameters - 1   -> derivatives of the delay wrt state
  177.         // freeStateParameters ... n       -> derivatives of the delay wrt tropospheric parameters
  178.         return Arrays.copyOfRange(derivatives, freeStateParameters, derivatives.length);
  179.     }

  181.     /** {@inheritDoc} */
  182.     @Override
  183.     public List<ParameterDriver> getParametersDrivers() {
  184.         return tropoModel.getParametersDrivers();
  185.     }

  187.     /** {@inheritDoc} */
  188.     @Override
  189.     public void modifyWithoutDerivatives(final EstimatedMeasurementBase<Phase> estimated) {

  191.         final Phase           measurement = estimated.getObservedMeasurement();
  192.         final GroundStation   station     = measurement.getStation();
  193.         final SpacecraftState state       = estimated.getStates()[0];

  195.         // Update estimated value taking into account the tropospheric delay.
  196.         // The tropospheric delay is directly added to the phase.
  197.         final double[] newValue = estimated.getEstimatedValue();
  198.         final double delay = phaseErrorTroposphericModel(station, state, measurement.getWavelength());
  199.         newValue[0] = newValue[0] + delay;
  200.         estimated.modifyEstimatedValue(this, newValue);

  202.     }

  204.     /** {@inheritDoc} */
  205.     @Override
  206.     public void modify(final EstimatedMeasurement<Phase> estimated) {
  207.         final Phase           measurement = estimated.getObservedMeasurement();
  208.         final GroundStation   station     = measurement.getStation();
  209.         final SpacecraftState state       = estimated.getStates()[0];

  211.         // update estimated derivatives with Jacobian of the measure wrt state
  212.         final ModifierGradientConverter converter = new ModifierGradientConverter(state, 6, new FrameAlignedProvider(state.getFrame()));
  213.         final FieldSpacecraftState<Gradient> gState = converter.getState(tropoModel);
  214.         final Gradient[] gParameters = converter.getParametersAtStateDate(gState, tropoModel);
  215.         final Gradient gDelay = phaseErrorTroposphericModel(station, gState, gParameters, measurement.getWavelength());
  216.         final double[] derivatives = gDelay.getGradient();

  218.         // Update state derivatives
  219.         final double[][] djac = phaseErrorJacobianState(derivatives);
  220.         final double[][] stateDerivatives = estimated.getStateDerivatives(0);
  221.         for (int irow = 0; irow < stateDerivatives.length; ++irow) {
  222.             for (int jcol = 0; jcol < stateDerivatives[0].length; ++jcol) {
  223.                 stateDerivatives[irow][jcol] += djac[irow][jcol];
  224.             }
  225.         }
  226.         estimated.setStateDerivatives(0, stateDerivatives);


  229.         // Update tropospheric parameter derivatives
  230.         int index = 0;
  231.         for (final ParameterDriver driver : getParametersDrivers()) {
  232.             if (driver.isSelected()) {
  233.                 for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {

  235.                     // update estimated derivatives with derivative of the modification wrt tropospheric parameters
  236.                     double parameterDerivative = estimated.getParameterDerivatives(driver, span.getStart())[0];
  237.                     final double[] dDelaydP    = phaseErrorParameterDerivative(derivatives, converter.getFreeStateParameters());
  238.                     parameterDerivative += dDelaydP[index];
  239.                     estimated.setParameterDerivatives(driver, span.getStart(), parameterDerivative);
  240.                     index = index + 1;
  241.                 }
  242.             }
  243.         }

  245.         // Update station parameter derivatives
  246.         for (final ParameterDriver driver : Arrays.asList(station.getClockOffsetDriver(),
  247.                                                           station.getEastOffsetDriver(),
  248.                                                           station.getNorthOffsetDriver(),
  249.                                                           station.getZenithOffsetDriver())) {
  250.             if (driver.isSelected()) {
  251.                 for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
  252.                     // update estimated derivatives with derivative of the modification wrt station parameters
  253.                     double parameterDerivative = estimated.getParameterDerivatives(driver, span.getStart())[0];
  254.                     parameterDerivative += phaseErrorParameterDerivative(station, driver, state, measurement.getWavelength());
  255.                     estimated.setParameterDerivatives(driver, span.getStart(), parameterDerivative);
  256.                 }
  257.             }
  258.         }

  260.         // Update estimated value taking into account the tropospheric delay.
  261.         modifyWithoutDerivatives(estimated);

  263.     }

  265. }
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