PhaseBuilder.java

  1. /* Copyright 2002-2021 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;

  18. import org.hipparchus.random.CorrelatedRandomVectorGenerator;
  19. import org.orekit.estimation.measurements.EstimationModifier;
  20. import org.orekit.estimation.measurements.GroundStation;
  21. import org.orekit.estimation.measurements.ObservableSatellite;
  22. import org.orekit.estimation.measurements.generation.AbstractMeasurementBuilder;
  23. import org.orekit.propagation.SpacecraftState;
  24. import org.orekit.time.AbsoluteDate;
  25. import org.orekit.utils.ParameterDriver;


  26. /** Builder for {@link Phase} measurements.
  27.  * @author Luc Maisonobe
  28.  * @since 10.1
  29.  */
  30. public class PhaseBuilder extends AbstractMeasurementBuilder<Phase> {

  31.     /** Ground station from which measurement is performed. */
  32.     private final GroundStation station;

  33.     /** Wavelength of the phase observed value [m]. */
  34.     private final double wavelength;

  35.     /** Simple constructor.
  36.      * @param noiseSource noise source, may be null for generating perfect measurements
  37.      * @param station ground station from which measurement is performed
  38.      * @param wavelength phase observed value wavelength (m)
  39.      * @param sigma theoretical standard deviation
  40.      * @param baseWeight base weight
  41.      * @param satellite satellite related to this builder
  42.      */
  43.     public PhaseBuilder(final CorrelatedRandomVectorGenerator noiseSource,
  44.                         final GroundStation station, final double wavelength,
  45.                         final double sigma, final double baseWeight,
  46.                         final ObservableSatellite satellite) {
  47.         super(noiseSource, sigma, baseWeight, satellite);
  48.         this.station    = station;
  49.         this.wavelength = wavelength;
  50.     }

  51.     /** {@inheritDoc} */
  52.     @Override
  53.     public Phase build(final SpacecraftState[] states) {

  54.         final ObservableSatellite satellite = getSatellites()[0];
  55.         final double sigma                  = getTheoreticalStandardDeviation()[0];
  56.         final double baseWeight             = getBaseWeight()[0];
  57.         final SpacecraftState[] relevant    = new SpacecraftState[] { states[satellite.getPropagatorIndex()] };

  58.         // create a dummy measurement
  59.         final Phase dummy = new Phase(station, relevant[0].getDate(), Double.NaN, wavelength, sigma, baseWeight, satellite);
  60.         for (final EstimationModifier<Phase> modifier : getModifiers()) {
  61.             dummy.addModifier(modifier);
  62.         }

  63.         // set a reference date for parameters missing one
  64.         for (final ParameterDriver driver : dummy.getParametersDrivers()) {
  65.             if (driver.getReferenceDate() == null) {
  66.                 final AbsoluteDate start = getStart();
  67.                 final AbsoluteDate end   = getEnd();
  68.                 driver.setReferenceDate(start.durationFrom(end) <= 0 ? start : end);
  69.             }
  70.         }

  71.         // estimate the perfect value of the measurement
  72.         double phase = dummy.estimate(0, 0, relevant).getEstimatedValue()[0];

  73.         // add the noise
  74.         final double[] noise = getNoise();
  75.         if (noise != null) {
  76.             phase += noise[0];
  77.         }

  78.         // generate measurement
  79.         final Phase measurement = new Phase(station, relevant[0].getDate(), phase, wavelength, sigma, baseWeight, satellite);
  80.         for (final EstimationModifier<Phase> modifier : getModifiers()) {
  81.             measurement.addModifier(modifier);
  82.         }
  83.         return measurement;

  84.     }

  85. }