FieldLongitudeRangeCrossingDetector.java
/* Copyright 2023-2024 Alberto Ferrero
* 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.
* Alberto Ferrero 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.propagation.events;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.Field;
import org.hipparchus.util.FastMath;
import org.orekit.bodies.FieldGeodeticPoint;
import org.orekit.bodies.OneAxisEllipsoid;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.events.handlers.FieldEventHandler;
import org.orekit.propagation.events.handlers.FieldStopOnIncreasing;
import org.orekit.propagation.events.intervals.FieldAdaptableInterval;
/** Detector for geographic longitude crossing.
* <p>This detector identifies when a spacecraft crosses a fixed
* longitude range with respect to a central body.</p>
* @author Alberto Ferrero
* @since 12.0
* @param <T> type of the field elements
*/
public class FieldLongitudeRangeCrossingDetector <T extends CalculusFieldElement<T>>
extends FieldAbstractDetector<FieldLongitudeRangeCrossingDetector<T>, T> {
/**
* Body on which the longitude is defined.
*/
private final OneAxisEllipsoid body;
/**
* Fixed longitude to be crossed, lower boundary in radians.
*/
private final double fromLongitude;
/**
* Fixed longitude to be crossed, upper boundary in radians.
*/
private final double toLongitude;
/**
* Sign, to get reversed inclusion longitude range (lower > upper).
*/
private final double sign;
/**
* Build a new detector.
* <p>The new instance uses default values for maximal checking interval
* ({@link #DEFAULT_MAX_CHECK}) and convergence threshold ({@link
* #DEFAULT_THRESHOLD}).</p>
* @param field the type of numbers to use.
* @param body body on which the longitude is defined
* @param fromLongitude longitude to be crossed, lower range boundary
* @param toLongitude longitude to be crossed, upper range boundary
*/
public FieldLongitudeRangeCrossingDetector(final Field<T> field, final OneAxisEllipsoid body,
final double fromLongitude, final double toLongitude) {
this(new FieldEventDetectionSettings<>(field, EventDetectionSettings.getDefaultEventDetectionSettings()),
new FieldStopOnIncreasing<>(), body, fromLongitude, toLongitude);
}
/**
* Build a detector.
*
* @param maxCheck maximal checking interval (s)
* @param threshold convergence threshold (s)
* @param body body on which the longitude is defined
* @param fromLongitude longitude to be crossed, lower range boundary
* @param toLongitude longitude to be crossed, upper range boundary
*/
public FieldLongitudeRangeCrossingDetector(final T maxCheck, final T threshold,
final OneAxisEllipsoid body, final double fromLongitude, final double toLongitude) {
this(new FieldEventDetectionSettings<>(FieldAdaptableInterval.of(maxCheck.getReal()), threshold, DEFAULT_MAX_ITER),
new FieldStopOnIncreasing<>(),
body,
fromLongitude,
toLongitude);
}
/**
* Protected constructor with full parameters.
* <p>
* This constructor is private as users are expected to use the builder
* API with the various {@code withXxx()} methods to set up the instance
* in a readable manner without using a huge amount of parameters.
* </p>
*
* @param detectionSettings event detection settings
* @param handler event handler to call at event occurrences
* @param body body on which the longitude is defined
* @param fromLongitude longitude to be crossed, lower range boundary
* @param toLongitude longitude to be crossed, upper range
* @since 13.0
*/
protected FieldLongitudeRangeCrossingDetector(final FieldEventDetectionSettings<T> detectionSettings,
final FieldEventHandler<T> handler,
final OneAxisEllipsoid body,
final double fromLongitude,
final double toLongitude) {
super(detectionSettings, handler);
this.body = body;
this.fromLongitude = ensureLongitudePositiveContinuity(fromLongitude);
this.toLongitude = ensureLongitudePositiveContinuity(toLongitude);
this.sign = FastMath.signum(this.toLongitude - this.fromLongitude);
}
/**
* {@inheritDoc}
*/
@Override
protected FieldLongitudeRangeCrossingDetector<T> create(final FieldEventDetectionSettings<T> detectionSettings,
final FieldEventHandler<T> newHandler) {
return new FieldLongitudeRangeCrossingDetector<>(detectionSettings, newHandler,
body, fromLongitude, toLongitude);
}
/**
* Get the body on which the geographic zone is defined.
*
* @return body on which the geographic zone is defined
*/
public OneAxisEllipsoid getBody() {
return body;
}
/** Get the fixed longitude range to be crossed (radians), lower boundary.
* @return fixed lower boundary longitude range to be crossed (radians)
*/
public double getFromLongitude() {
return getLongitudeOverOriginalRange(fromLongitude);
}
/** Get the fixed longitude range to be crossed (radians), upper boundary.
* @return fixed upper boundary longitude range to be crossed (radians)
*/
public double getToLongitude() {
return getLongitudeOverOriginalRange(toLongitude);
}
/**
* Ensure continuity for negative angles, as longitude defined as [-PI, PI], transform negative to positive.
* New longitude angle definition from [0, 2 PI].
*
* @param longitude original longitude value
* @return positive range longitude
*/
private T ensureFieldLongitudePositiveContinuity(final T longitude) {
return longitude.getReal() < 0 ? longitude.add(2 * FastMath.PI) : longitude;
}
/**
* Ensure continuity for negative angles, as longitude defined as [-PI, PI], transform negative to positive.
* New longitude angle definition from [0, 2 PI].
*
* @param longitude original longitude value
* @return positive range longitude
*/
private double ensureLongitudePositiveContinuity(final double longitude) {
return longitude < 0 ? longitude + 2 * FastMath.PI : longitude;
}
/**
* Get longitude shifted over the original range [-PI, PI].
* @param longitude longitude value to convert
* @return original range longitude
*/
private double getLongitudeOverOriginalRange(final double longitude) {
return longitude > FastMath.PI ? longitude - 2 * FastMath.PI : longitude;
}
/**
* Compute the value of the detection function.
* <p>
* The value is positive if the spacecraft longitude is inside the longitude range.
* The longitude value is reflected from [-PI, +PI] to [0, 2 PI] to ensure continuity.
* </p>
*
* @param s the current state information: date, kinematics, attitude
* @return positive if spacecraft inside the range
*/
public T g(final FieldSpacecraftState<T> s) {
// convert state to geodetic coordinates
final FieldGeodeticPoint<T> gp = body.transform(s.getPVCoordinates().getPosition(),
s.getFrame(), s.getDate());
// point longitude
final T longitude = ensureFieldLongitudePositiveContinuity(gp.getLongitude());
// inside or outside latitude range
return longitude.subtract(fromLongitude).multiply(longitude.negate().add(toLongitude)).multiply(sign);
}
}