PositionBuilder.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.  * 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.generation;

  18. import java.util.Map;

  19. import org.hipparchus.geometry.euclidean.threed.Vector3D;
  20. import org.hipparchus.random.CorrelatedRandomVectorGenerator;
  21. import org.orekit.estimation.measurements.EstimationModifier;
  22. import org.orekit.estimation.measurements.ObservableSatellite;
  23. import org.orekit.estimation.measurements.Position;
  24. import org.orekit.propagation.SpacecraftState;
  25. import org.orekit.propagation.sampling.OrekitStepInterpolator;
  26. import org.orekit.time.AbsoluteDate;
  27. import org.orekit.utils.ParameterDriver;


  28. /** Builder for {@link Position} measurements.
  29.  * @author Luc Maisonobe
  30.  * @since 9.3
  31.  */
  32. public class PositionBuilder extends AbstractMeasurementBuilder<Position> {

  33.     /** Satellite related to this builder.
  34.      * @since 12.0
  35.      */
  36.     private final ObservableSatellite satellite;

  37.     /** Simple constructor.
  38.      * @param noiseSource noise source, may be null for generating perfect measurements
  39.      * @param sigma theoretical standard deviation
  40.      * @param baseWeight base weight
  41.      * @param satellite satellite related to this builder
  42.      */
  43.     public PositionBuilder(final CorrelatedRandomVectorGenerator noiseSource,
  44.                            final double sigma, final double baseWeight,
  45.                            final ObservableSatellite satellite) {
  46.         super(noiseSource, sigma, baseWeight, satellite);
  47.         this.satellite = satellite;
  48.     }

  49.     /** {@inheritDoc} */
  50.     @Override
  51.     public Position build(final AbsoluteDate date, final Map<ObservableSatellite, OrekitStepInterpolator> interpolators) {

  52.         final double sigma                  = getTheoreticalStandardDeviation()[0];
  53.         final double baseWeight             = getBaseWeight()[0];
  54.         final SpacecraftState[] relevant    = new SpacecraftState[] { interpolators.get(satellite).getInterpolatedState(date) };

  55.         // create a dummy measurement
  56.         final Position dummy = new Position(relevant[0].getDate(), Vector3D.NaN, sigma, baseWeight, satellite);
  57.         for (final EstimationModifier<Position> modifier : getModifiers()) {
  58.             dummy.addModifier(modifier);
  59.         }

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

  68.         // estimate the perfect value of the measurement
  69.         final double[] position = dummy.estimateWithoutDerivatives(0, 0, relevant).getEstimatedValue();

  70.         // add the noise
  71.         final double[] noise = getNoise();
  72.         if (noise != null) {
  73.             position[0] += noise[0];
  74.             position[1] += noise[1];
  75.             position[2] += noise[2];
  76.         }

  77.         // generate measurement
  78.         final Position measurement = new Position(relevant[0].getDate(), new Vector3D(position),
  79.                                                   sigma, baseWeight, satellite);
  80.         for (final EstimationModifier<Position> modifier : getModifiers()) {
  81.             measurement.addModifier(modifier);
  82.         }
  83.         return measurement;

  84.     }

  85. }