ResidualFilter.java
/* Copyright 2002-2024 CS GROUP
* Licensed to CS GROUP (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.orekit.estimation.measurements.filtering;
import org.hipparchus.util.FastMath;
import org.orekit.estimation.measurements.EstimatedMeasurementBase;
import org.orekit.estimation.measurements.ObservedMeasurement;
import org.orekit.propagation.SpacecraftState;
/**
* Residual pre-processing filter.
* <p>
* The measurement residual is defined by the difference between
* the observed value and the estimated value of the measurement.
* </p>
* @param <T> the type of the measurement
* @author Bryan Cazabonne
* @author David Soulard
* @since 10.2
*/
public class ResidualFilter<T extends ObservedMeasurement<T>> implements MeasurementFilter<T> {
/** Threshold over which the measurement will be rejected. */
private final double threshold;
/**
* Constructor.
* @param threshold maximum value for the measurement residual
*/
public ResidualFilter(final double threshold) {
this.threshold = threshold;
}
/** {@inheritDoc} */
@Override
public void filter(final ObservedMeasurement<T> measurement, final SpacecraftState state) {
// Computation of the estimated value of the measurement
final SpacecraftState[] sc = new SpacecraftState[] {state};
final EstimatedMeasurementBase<T> estimated = measurement.estimateWithoutDerivatives(sc);
final double[] estimatedValue = estimated.getEstimatedValue();
// Observed parameters (i.e. value and standard deviation)
final double[] observedValue = measurement.getObservedValue();
final double[] sigma = measurement.getTheoreticalStandardDeviation();
// Check if observed value is not too far from estimation
for (int i = 0; i < observedValue.length; i++) {
if (FastMath.abs(observedValue[i] - estimatedValue[i]) > threshold * sigma[i]) {
// Observed value is too far, measurement is disabled
measurement.setEnabled(false);
}
}
}
}