FieldLatitudeCrossingDetector.java
/* Copyright 2002-2022 CS GROUP
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* 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
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*
* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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package org.orekit.propagation.events;
import org.hipparchus.Field;
import org.hipparchus.CalculusFieldElement;
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;
/** Detector for geographic latitude crossing.
* <p>This detector identifies when a spacecraft crosses a fixed
* latitude with respect to a central body.</p>
* @author Luc Maisonobe
* @author Evan Ward
* @since 9.3
*/
public class FieldLatitudeCrossingDetector <T extends CalculusFieldElement<T>>
extends FieldAbstractDetector<FieldLatitudeCrossingDetector<T>, T> {
/** Body on which the latitude is defined. */
private OneAxisEllipsoid body;
/** Fixed latitude to be crossed. */
private final double latitude;
/** Build a new detector.
* <p>The new instance uses default values for maximal checking interval
* ({@link #DEFAULT_MAXCHECK}) and convergence threshold ({@link
* #DEFAULT_THRESHOLD}).</p>
* @param field the type of numbers to use.
* @param body body on which the latitude is defined
* @param latitude latitude to be crossed
*/
public FieldLatitudeCrossingDetector(final Field<T> field,
final OneAxisEllipsoid body,
final double latitude) {
this(field.getZero().add(DEFAULT_MAXCHECK),
field.getZero().add(DEFAULT_THRESHOLD),
body,
latitude);
}
/** Build a detector.
* @param maxCheck maximal checking interval (s)
* @param threshold convergence threshold (s)
* @param body body on which the latitude is defined
* @param latitude latitude to be crossed
*/
public FieldLatitudeCrossingDetector(final T maxCheck,
final T threshold,
final OneAxisEllipsoid body,
final double latitude) {
this(maxCheck, threshold, DEFAULT_MAX_ITER, new FieldStopOnIncreasing<>(),
body, latitude);
}
/** Private 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 maxCheck maximum checking interval (s)
* @param threshold convergence threshold (s)
* @param maxIter maximum number of iterations in the event time search
* @param handler event handler to call at event occurrences
* @param body body on which the latitude is defined
* @param latitude latitude to be crossed
*/
private FieldLatitudeCrossingDetector(
final T maxCheck,
final T threshold,
final int maxIter,
final FieldEventHandler<? super FieldLatitudeCrossingDetector<T>, T> handler,
final OneAxisEllipsoid body,
final double latitude) {
super(maxCheck, threshold, maxIter, handler);
this.body = body;
this.latitude = latitude;
}
/** {@inheritDoc} */
@Override
protected FieldLatitudeCrossingDetector<T> create(
final T newMaxCheck,
final T newThreshold,
final int newMaxIter,
final FieldEventHandler<? super FieldLatitudeCrossingDetector<T>, T> newHandler) {
return new FieldLatitudeCrossingDetector<>(
newMaxCheck, newThreshold, newMaxIter, newHandler, body, latitude);
}
/** 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 latitude to be crossed (radians).
* @return fixed latitude to be crossed (radians)
*/
public double getLatitude() {
return latitude;
}
/** Compute the value of the detection function.
* <p>
* The value is the spacecraft latitude minus the fixed latitude to be crossed.
* It is positive if the spacecraft is northward and negative if it is southward
* with respect to the fixed latitude.
* </p>
* @param s the current state information: date, kinematics, attitude
* @return spacecraft latitude minus the fixed latitude to be crossed
*/
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());
// latitude difference
return gp.getLatitude().subtract(latitude);
}
}