FieldLatitudeRangeCrossingDetector.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;
/** Detector for geographic latitude crossing.
* <p>This detector identifies when a spacecraft crosses a fixed
* latitude range with respect to a central body.</p>
* @author Alberto Ferrero
* @since 12.0
* @param <T> type of the field elements
*/
public class FieldLatitudeRangeCrossingDetector <T extends CalculusFieldElement<T>>
extends FieldAbstractDetector<FieldLatitudeRangeCrossingDetector<T>, T> {
/**
* Body on which the latitude is defined.
*/
private final OneAxisEllipsoid body;
/**
* Fixed latitude to be crossed, lower boundary in radians.
*/
private final double fromLatitude;
/**
* Fixed latitude to be crossed, upper boundary in radians.
*/
private final double toLatitude;
/**
* Sign, to get reversed inclusion latitude range (lower > upper).
*/
private final double sign;
/**
* 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 fromLatitude latitude to be crossed, lower range boundary
* @param toLatitude latitude to be crossed, upper range boundary
*/
public FieldLatitudeRangeCrossingDetector(final Field<T> field,
final OneAxisEllipsoid body,
final double fromLatitude,
final double toLatitude) {
this(FieldAdaptableInterval.of(DEFAULT_MAXCHECK),
field.getZero().add(DEFAULT_THRESHOLD),
DEFAULT_MAX_ITER,
new FieldStopOnIncreasing<>(),
body,
fromLatitude,
toLatitude);
}
/**
* Build a detector.
*
* @param maxCheck maximal checking interval (s)
* @param threshold convergence threshold (s)
* @param body body on which the latitude is defined
* @param fromLatitude latitude to be crossed, lower range boundary
* @param toLatitude latitude to be crossed, upper range boundary
*/
public FieldLatitudeRangeCrossingDetector(final T maxCheck, final T threshold,
final OneAxisEllipsoid body, final double fromLatitude, final double toLatitude) {
this(FieldAdaptableInterval.of(maxCheck.getReal()), threshold, DEFAULT_MAX_ITER, new FieldStopOnIncreasing<>(),
body, fromLatitude, toLatitude);
}
/**
* 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 fromLatitude latitude to be crossed, lower range boundary
* @param toLatitude latitude to be crossed, upper range boundary
*/
protected FieldLatitudeRangeCrossingDetector(final FieldAdaptableInterval<T> maxCheck,
final T threshold,
final int maxIter,
final FieldEventHandler<T> handler,
final OneAxisEllipsoid body,
final double fromLatitude,
final double toLatitude) {
super(maxCheck, threshold, maxIter, handler);
this.body = body;
this.fromLatitude = fromLatitude;
this.toLatitude = toLatitude;
this.sign = FastMath.signum(toLatitude - fromLatitude);
}
/**
* {@inheritDoc}
*/
@Override
protected FieldLatitudeRangeCrossingDetector<T> create(final FieldAdaptableInterval<T> newMaxCheck,
final T newThreshold,
final int newMaxIter,
final FieldEventHandler<T> newHandler) {
return new FieldLatitudeRangeCrossingDetector<>(newMaxCheck, newThreshold, newMaxIter, newHandler,
body, fromLatitude, toLatitude);
}
/**
* 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 range to be crossed (radians), lower boundary.
*
* @return fixed lower boundary latitude range to be crossed (radians)
*/
public double getFromLatitude() {
return fromLatitude;
}
/**
* Get the fixed latitude range to be crossed (radians), upper boundary.
*
* @return fixed lower boundary latitude range to be crossed (radians)
*/
public double getToLatitude() {
return toLatitude;
}
/**
* Compute the value of the detection function.
* <p>
* The value is positive if the spacecraft latitude is inside the latitude range.
* It is positive if the spacecraft is northward to lower boundary range and southward to upper boundary range,
* with respect to the fixed latitude range.
* </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 latitude
final T latitude = gp.getLatitude();
// inside or outside latitude range
return latitude.subtract(fromLatitude).multiply(latitude.negate().add(toLatitude)).multiply(sign);
}
}