ElevationDetector.java
/* Copyright 2002-2021 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,
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* See the License for the specific language governing permissions and
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*/
package org.orekit.propagation.events;
import org.hipparchus.ode.events.Action;
import org.orekit.frames.TopocentricFrame;
import org.orekit.models.AtmosphericRefractionModel;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.handlers.EventHandler;
import org.orekit.propagation.events.handlers.StopOnDecreasing;
import org.orekit.utils.ElevationMask;
/**
* Finder for satellite raising/setting events that allows for the
* setting of azimuth and/or elevation bounds or a ground azimuth/elevation
* mask input. Each calculation be configured to use atmospheric refraction
* as well.
* <p>The default implementation behavior is to {@link Action#CONTINUE continue}
* propagation at raising and to {@link Action#STOP stop} propagation
* at setting. This can be changed by calling
* {@link #withHandler(EventHandler)} after construction.</p>
* @author Hank Grabowski
* @since 6.1
*/
public class ElevationDetector extends AbstractDetector<ElevationDetector> {
/** Elevation mask used for calculations, if defined. */
private final ElevationMask elevationMask;
/** Minimum elevation value used if mask is not defined. */
private final double minElevation;
/** Atmospheric Model used for calculations, if defined. */
private final AtmosphericRefractionModel refractionModel;
/** Topocentric frame in which elevation should be evaluated. */
private final TopocentricFrame topo;
/**
* Creates an instance of Elevation detector based on passed in topocentric frame
* and the minimum elevation angle.
* <p>
* uses default values for maximal checking interval ({@link #DEFAULT_MAXCHECK})
* and convergence threshold ({@link #DEFAULT_THRESHOLD}).</p>
* @param topo reference to a topocentric model
* @see #withConstantElevation(double)
* @see #withElevationMask(ElevationMask)
* @see #withRefraction(AtmosphericRefractionModel)
*/
public ElevationDetector(final TopocentricFrame topo) {
this(DEFAULT_MAXCHECK, DEFAULT_THRESHOLD, topo);
}
/**
* Creates an instance of Elevation detector based on passed in topocentric frame
* and overrides of default maximal checking interval and convergence threshold values.
* @param maxCheck maximum checking interval (s)
* @param threshold maximum divergence threshold (s)
* @param topo reference to a topocentric model
* @see #withConstantElevation(double)
* @see #withElevationMask(ElevationMask)
* @see #withRefraction(AtmosphericRefractionModel)
*/
public ElevationDetector(final double maxCheck, final double threshold,
final TopocentricFrame topo) {
this(maxCheck, threshold, DEFAULT_MAX_ITER,
new StopOnDecreasing<ElevationDetector>(),
0.0, null, null, topo);
}
/** 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 minElevation minimum elevation in radians (rad)
* @param mask reference to elevation mask
* @param refractionModel reference to refraction model
* @param topo reference to a topocentric model
*/
private ElevationDetector(final double maxCheck, final double threshold,
final int maxIter, final EventHandler<? super ElevationDetector> handler,
final double minElevation, final ElevationMask mask,
final AtmosphericRefractionModel refractionModel,
final TopocentricFrame topo) {
super(maxCheck, threshold, maxIter, handler);
this.minElevation = minElevation;
this.elevationMask = mask;
this.refractionModel = refractionModel;
this.topo = topo;
}
/** {@inheritDoc} */
@Override
protected ElevationDetector create(final double newMaxCheck, final double newThreshold,
final int newMaxIter, final EventHandler<? super ElevationDetector> newHandler) {
return new ElevationDetector(newMaxCheck, newThreshold, newMaxIter, newHandler,
minElevation, elevationMask, refractionModel, topo);
}
/**
* Returns the currently configured elevation mask.
* @return elevation mask
* (null if instance has been configured with {@link #withConstantElevation(double)}
* @see #withElevationMask(ElevationMask)
*/
public ElevationMask getElevationMask() {
return this.elevationMask;
}
/**
* Returns the currently configured minimum valid elevation value.
* @return minimum elevation value
* ({@code Double.NaN} if instance has been configured with {@link #withElevationMask(ElevationMask)}
* @see #withConstantElevation(double)
*/
public double getMinElevation() {
return this.minElevation;
}
/**
* Returns the currently configured refraction model.
* @return refraction model
* @see #withRefraction(AtmosphericRefractionModel)
*/
public AtmosphericRefractionModel getRefractionModel() {
return this.refractionModel;
}
/**
* Returns the currently configured topocentric frame definitions.
* @return topocentric frame definition
*/
public TopocentricFrame getTopocentricFrame() {
return this.topo;
}
/** Compute the value of the switching function.
* This function measures the difference between the current elevation
* (and azimuth if necessary) and the reference mask or minimum value.
* @param s the current state information: date, kinematics, attitude
* @return value of the switching function
*/
@Override
public double g(final SpacecraftState s) {
final double trueElevation = topo.getElevation(s.getPVCoordinates().getPosition(),
s.getFrame(), s.getDate());
final double calculatedElevation;
if (refractionModel != null) {
calculatedElevation = trueElevation + refractionModel.getRefraction(trueElevation);
} else {
calculatedElevation = trueElevation;
}
if (elevationMask != null) {
final double azimuth = topo.getAzimuth(s.getPVCoordinates().getPosition(), s.getFrame(), s.getDate());
return calculatedElevation - elevationMask.getElevation(azimuth);
} else {
return calculatedElevation - minElevation;
}
}
/**
* Setup the minimum elevation for detection.
* <p>
* This will override an elevation mask if it has been configured as such previously.
* </p>
* @param newMinElevation minimum elevation for visibility in radians (rad)
* @return a new detector with updated configuration (the instance is not changed)
* @see #getMinElevation()
* @since 6.1
*/
public ElevationDetector withConstantElevation(final double newMinElevation) {
return new ElevationDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
newMinElevation, null, refractionModel, topo);
}
/**
* Setup the elevation mask for detection using the passed in mask object.
* @param newElevationMask elevation mask to use for the computation
* @return a new detector with updated configuration (the instance is not changed)
* @since 6.1
* @see #getElevationMask()
*/
public ElevationDetector withElevationMask(final ElevationMask newElevationMask) {
return new ElevationDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
Double.NaN, newElevationMask, refractionModel, topo);
}
/**
* Setup the elevation detector to use an atmospheric refraction model in its
* calculations.
* <p>
* To disable the refraction when copying an existing elevation
* detector, call this method with a null argument.
* </p>
* @param newRefractionModel refraction model to use for the computation
* @return a new detector with updated configuration (the instance is not changed)
* @since 6.1
* @see #getRefractionModel()
*/
public ElevationDetector withRefraction(final AtmosphericRefractionModel newRefractionModel) {
return new ElevationDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
minElevation, elevationMask, newRefractionModel, topo);
}
}