AbstractDualFrequencyCombination.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.ArrayList;
  20. import java.util.Arrays;
  21. import java.util.List;

  23. import org.orekit.errors.OrekitException;
  24. import org.orekit.errors.OrekitMessages;
  25. import org.orekit.files.rinex.observation.ObservationData;
  26. import org.orekit.files.rinex.observation.ObservationDataSet;
  27. import org.orekit.gnss.GnssSignal;
  28. import org.orekit.gnss.MeasurementType;
  29. import org.orekit.gnss.ObservationType;
  30. import org.orekit.gnss.SatelliteSystem;
  31. import org.orekit.utils.Constants;

  33. /** Base class for dual frequency combination of measurements.
  34.  * @author Bryan Cazabonne
  35.  * @since 10.1
  36.  */
  37. public abstract class AbstractDualFrequencyCombination implements MeasurementCombination {

  39.     /** Type of combination of measurements. */
  40.     private final CombinationType type;

  42.     /** Satellite system used for the combination. */
  43.     private final SatelliteSystem system;

  45.     /**
  46.      * Constructor.
  47.      * @param type combination of measurements type
  48.      * @param system satellite system
  49.      */
  50.     protected AbstractDualFrequencyCombination(final CombinationType type, final SatelliteSystem system) {
  51.         this.type   = type;
  52.         this.system = system;
  53.     }

  55.     /** {@inheritDoc} */
  56.     @Override
  57.     public String getName() {
  58.         return type.getName();
  59.     }

  61.     /**
  62.      * Combines observation data using a dual frequency combination of measurements.
  63.      * @param od1 first observation data to combined
  64.      * @param od2 second observation data to combined
  65.      * @return a combined observation data
  66.      */
  67.     public CombinedObservationData combine(final ObservationData od1, final ObservationData od2) {

  69.         // Observation types
  70.         final ObservationType obsType1 = od1.getObservationType();
  71.         final ObservationType obsType2 = od2.getObservationType();

  73.         // Frequencies
  74.         final GnssSignal signal1 = obsType1.getSignal(system);
  75.         final GnssSignal signal2 = obsType2.getSignal(system);
  76.         // Check if the combination of measurements if performed for two different frequencies
  77.         if (signal1 == signal2) {
  78.             throw new OrekitException(OrekitMessages.INCOMPATIBLE_FREQUENCIES_FOR_COMBINATION_OF_MEASUREMENTS,
  79.                                       signal1.getFrequency(), signal2.getFrequency(), getName());
  80.         }

  82.         // Measurements types
  83.         final MeasurementType measType1 = obsType1.getMeasurementType();
  84.         final MeasurementType measType2 = obsType2.getMeasurementType();

  86.         // Check if measurement types are the same
  87.         if (measType1 != measType2) {
  88.             // If the measurement types are differents, an exception is thrown
  89.             throw new OrekitException(OrekitMessages.INVALID_MEASUREMENT_TYPES_FOR_COMBINATION_OF_MEASUREMENTS,
  90.                                       measType1, measType2, getName());
  91.         }

  93.         // Combined frequency
  94.         final double combinedFrequency = getCombinedFrequency(signal1, signal2);

  96.         // Combined value
  97.         final double combinedValue;
  98.         if (obsType1.getMeasurementType() == MeasurementType.CARRIER_PHASE && !Double.isNaN(combinedFrequency)) {
  99.             // Transform from cycle to meters measurements
  100.             final double obs1Meters = od1.getValue() * signal1.getWavelength();
  101.             final double obs2Meters = od2.getValue() * signal2.getWavelength();

  103.             // Calculate the combined value and convert it in cycles using the combined frequency
  104.             combinedValue = getCombinedValue(obs1Meters, signal1, obs2Meters, signal2) * combinedFrequency / Constants.SPEED_OF_LIGHT;
  105.         } else {
  106.             combinedValue = getCombinedValue(od1.getValue(), signal1, od2.getValue(), signal2);
  107.         }

  109.         // Combined observation data
  110.         return new CombinedObservationData(combinedValue, combinedFrequency, type, measType1, Arrays.asList(od1, od2));

  112.     }

  114.     /** {@inheritDoc} */
  115.     @Override
  116.     public CombinedObservationDataSet combine(final ObservationDataSet observations) {

  118.         // Initialize list of measurements
  119.         final List<ObservationData> pseudoRanges = new ArrayList<>();
  120.         final List<ObservationData> phases       = new ArrayList<>();

  122.         // Loop on observation data to fill lists
  123.         for (final ObservationData od : observations.getObservationData()) {
  124.             if (!Double.isNaN(od.getValue())) {
  125.                 if (od.getObservationType().getMeasurementType() == MeasurementType.PSEUDO_RANGE) {
  126.                     pseudoRanges.add(od);
  127.                 } else if (od.getObservationType().getMeasurementType() == MeasurementType.CARRIER_PHASE) {
  128.                     phases.add(od);
  129.                 }
  130.             }
  131.         }

  133.         // Initialize list of combined observation data
  134.         final List<CombinedObservationData> combined = new ArrayList<>();
  135.         // Combine pseudo-ranges
  136.         for (int i = 0; i < pseudoRanges.size() - 1; i++) {
  137.             for (int j = 1; j < pseudoRanges.size(); j++) {
  138.                 final boolean combine = isCombinationPossible(pseudoRanges.get(i), pseudoRanges.get(j));
  139.                 if (combine) {
  140.                     combined.add(combine(pseudoRanges.get(i), pseudoRanges.get(j)));
  141.                 }
  142.             }
  143.         }
  144.         // Combine carrier-phases
  145.         for (int i = 0; i < phases.size() - 1; i++) {
  146.             for (int j = 1; j < phases.size(); j++) {
  147.                 final boolean combine = isCombinationPossible(phases.get(i), phases.get(j));
  148.                 if (combine) {
  149.                     combined.add(combine(phases.get(i), phases.get(j)));
  150.                 }
  151.             }
  152.         }

  154.         return new CombinedObservationDataSet(observations.getSatellite().getSystem(),
  155.                                               observations.getSatellite().getPRN(),
  156.                                               observations.getDate(),
  157.                                               observations.getRcvrClkOffset(), combined);
  158.     }

  160.     /**
  161.      * Get the combined observed value of two measurements.
  162.      *
  163.      * @param obs1 observed value of the first measurement
  164.      * @param s1   frequency of the first measurement
  165.      * @param obs2 observed value of the second measurement
  166.      * @param s2   frequency of the second measurement
  167.      * @return combined observed value
  168.      */
  169.     protected abstract double getCombinedValue(double obs1, GnssSignal s1, double obs2, GnssSignal s2);

  171.     /**
  172.      * Get the combined frequency of two measurements.
  173.      *
  174.      * @param s1 frequency of the first measurement
  175.      * @param s2 frequency of the second measurement
  176.      * @return combined frequency in Hz
  177.      */
  178.     protected abstract double getCombinedFrequency(GnssSignal s1, GnssSignal s2);

  180.     /**
  181.      * Verifies if two observation data can be combined.
  182.      * @param data1 first observation data
  183.      * @param data2 second observation data
  184.      * @return true if observation data can be combined
  185.      */
  186.     private boolean isCombinationPossible(final ObservationData data1, final ObservationData data2) {
  187.         // Observation types
  188.         final ObservationType obsType1 = data1.getObservationType();
  189.         final ObservationType obsType2 = data2.getObservationType();
  190.         // Dual-frequency combination is possible only if observation code is the same and data frequencies are different
  191.         return obsType1.getSignal(system) != obsType2.getSignal(system) &&
  192.                obsType1.getSignalCode() == obsType2.getSignalCode();
  193.     }

  195. }
Created with JaCoCo 0.8.12.202403310830