LatitudeCrossingDetector.java
- /* Copyright 2002-2022 CS GROUP
- * 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.propagation.events;
- import org.orekit.bodies.OneAxisEllipsoid;
- import org.orekit.bodies.GeodeticPoint;
- import org.orekit.propagation.SpacecraftState;
- import org.orekit.propagation.events.handlers.EventHandler;
- import org.orekit.propagation.events.handlers.StopOnIncreasing;
- /** 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
- * @since 7.1
- */
- public class LatitudeCrossingDetector extends AbstractDetector<LatitudeCrossingDetector> {
- /** 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 body body on which the latitude is defined
- * @param latitude latitude to be crossed
- */
- public LatitudeCrossingDetector(final OneAxisEllipsoid body, final double latitude) {
- this(DEFAULT_MAXCHECK, 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 LatitudeCrossingDetector(final double maxCheck, final double threshold,
- final OneAxisEllipsoid body, final double latitude) {
- this(maxCheck, threshold, DEFAULT_MAX_ITER, new StopOnIncreasing<LatitudeCrossingDetector>(),
- 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 LatitudeCrossingDetector(final double maxCheck, final double threshold,
- final int maxIter, final EventHandler<? super LatitudeCrossingDetector> handler,
- final OneAxisEllipsoid body, final double latitude) {
- super(maxCheck, threshold, maxIter, handler);
- this.body = body;
- this.latitude = latitude;
- }
- /** {@inheritDoc} */
- @Override
- protected LatitudeCrossingDetector create(final double newMaxCheck, final double newThreshold,
- final int newMaxIter,
- final EventHandler<? super LatitudeCrossingDetector> newHandler) {
- return new LatitudeCrossingDetector(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 double g(final SpacecraftState s) {
- // convert state to geodetic coordinates
- final GeodeticPoint gp = body.transform(s.getPVCoordinates().getPosition(),
- s.getFrame(), s.getDate());
- // latitude difference
- return gp.getLatitude() - latitude;
- }
- }