PhaseCentersOffsetComputer.java
/* Copyright 2002-2024 Luc Maisonobe
* 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.modifiers;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.frames.StaticTransform;
import org.orekit.gnss.antenna.FrequencyPattern;
/** Compute phase centers offset on an emitter-receiver link.
* @author Luc Maisonobe
* @since 12.0
*/
public class PhaseCentersOffsetComputer {
/** Emitter pattern. */
private final FrequencyPattern emitterPattern;
/** Receiver pattern. */
private final FrequencyPattern receiverPattern;
/** Simple constructor.
* @param emitterPattern emitter pattern
* @param receiverPattern receiver pattern
*/
public PhaseCentersOffsetComputer(final FrequencyPattern emitterPattern,
final FrequencyPattern receiverPattern) {
this.emitterPattern = emitterPattern;
this.receiverPattern = receiverPattern;
}
/** Compute distance offset to be added to the distance between antennas reference points.
* @param emitterToInert transform from emitter to inertial frame at emission date
* @param receiverToInert transform from receiver to inertial frame at reception date
* @return offset to be added to distance between origins, in order to get distance between phase centers
*/
public double offset(final StaticTransform emitterToInert, final StaticTransform receiverToInert) {
// compute the relative positions of frames origins
final Vector3D emitterOrigin = emitterToInert.transformPosition(Vector3D.ZERO);
final Vector3D receiverOrigin = receiverToInert.transformPosition(Vector3D.ZERO);
final Vector3D deltaOrigins = receiverOrigin.subtract(emitterOrigin);
// compute the relative positions of mean phase centers
final Vector3D emitterMean = emitterToInert.transformPosition(emitterPattern.getEccentricities());
final Vector3D receiverMean = receiverToInert.transformPosition(receiverPattern.getEccentricities());
final Vector3D deltaMeans = receiverMean.subtract(emitterMean);
// compute the phase variation at emission
final Vector3D emitterLos = emitterToInert.getRotation().applyInverseTo(deltaMeans);
final double emitterPCV = emitterPattern.getPhaseCenterVariation(emitterLos);
// compute the phase variation at reception
final Vector3D receiverLos = receiverToInert.getRotation().applyInverseTo(deltaMeans.negate());
final double receiverPCV = receiverPattern.getPhaseCenterVariation(receiverLos);
// compute the total offset resulting from both antennas phase centers
return deltaMeans.getNorm() - deltaOrigins.getNorm() + emitterPCV + receiverPCV;
}
}