PhaseAmbiguityModifier.java

/* Copyright 2002-2018 CS Systèmes d'Information
 * Licensed to CS Systèmes d'Information (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
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package org.orekit.estimation.measurements.modifiers;

import java.util.Collections;
import java.util.List;

import org.hipparchus.util.FastMath;
import org.orekit.errors.OrekitException;
import org.orekit.estimation.measurements.EstimatedMeasurement;
import org.orekit.estimation.measurements.EstimationModifier;
import org.orekit.estimation.measurements.Phase;
import org.orekit.utils.ParameterDriver;

/** Class modifying theoretical phase measurement with ambiguity.
 *
 * @author Luc Maisonobe
 * @since 9.2
 */
public class PhaseAmbiguityModifier implements EstimationModifier<Phase> {

    /** Ambiguity scale factor.
     * <p>
     * We use a power of 2 to avoid numeric noise introduction
     * in the multiplications/divisions sequences.
     * </p>
     */
    private static final double AMBIGUITY_SCALE = FastMath.scalb(1.0, 26);

    /** Ambiguity parameter. */
    private final ParameterDriver ambiguity;

    /** Constructor.
     * <p>
     * It is expected that many different ambiguities will be used at the
     * same time during an orbit determination, therefore they are keyed
     * using a simple integer. All ambiguities using the same key will
     * be enforced to be equal. It is the responsibility of the caller to
     * use a proper counter to manage the ambiguities properly.
     * </p>
     * @param key key to identify the ambiguity
     * @param ambiguity initial value of ambiguity
     * @exception OrekitException if parameter scale is too close to zero (never happens)
     */
    public PhaseAmbiguityModifier(final int key, final double ambiguity)
        throws OrekitException {
        this.ambiguity = new ParameterDriver("amgiguity-" + key,
                                             ambiguity, AMBIGUITY_SCALE,
                                             Double.NEGATIVE_INFINITY,
                                             Double.POSITIVE_INFINITY);
    }

    /** {@inheritDoc} */
    @Override
    public List<ParameterDriver> getParametersDrivers() {
        return Collections.singletonList(ambiguity);
    }

    @Override
    public void modify(final EstimatedMeasurement<Phase> estimated)
        throws OrekitException {

        // apply the ambiguity to the measurement value
        final double[] value = estimated.getEstimatedValue();
        value[0] += ambiguity.getValue();
        if (ambiguity.isSelected()) {
            // add the partial derivatives
            estimated.setParameterDerivatives(ambiguity, 1.0);
        }
        estimated.setEstimatedValue(value);

    }

}