org.orekit.utils.ElevationMask Maven / Gradle / Ivy
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/* Copyright 2013 Applied Defense Solutions, Inc.
* Licensed to CS Communication & Systèmes (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.utils;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Comparator;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.MathUtils;
import org.orekit.errors.OrekitIllegalArgumentException;
import org.orekit.errors.OrekitMessages;
/**
* Class for modeling the ground elevation values around a given point.
*
* Instances of this class can be considered to be immutable
* @author Hank Grabowski
* @since 6.1
*/
public class ElevationMask implements Serializable {
/** Serializable UID. */
private static final long serialVersionUID = 20131118L;
/** Azimuth-elevation mask. */
private final double[][] azelmask;
/**
* Creates an instance of an Elevation mask based on the passed in parameter.
* @param mask azimuth-elevation mask (rad). First column (i.e. mask[i][0])
* should contain azimuth values and the second column (i.e. mask[i][1])
* should contain corresponding elevations
*/
public ElevationMask(final double[][] mask) {
this.azelmask = checkMask(mask);
}
/** Get the interpolated elevation for a given azimuth according to the mask.
* @param azimuth azimuth (rad)
* @return elevation angle (rad)
*/
public double getElevation(final double azimuth) {
double elevation = 0.0;
boolean fin = false;
for (int i = 1; i < azelmask.length & !fin; i++) {
if (azimuth <= azelmask[i][0]) {
fin = true;
final double azd = azelmask[i - 1][0];
final double azf = azelmask[i][0];
final double eld = azelmask[i - 1][1];
final double elf = azelmask[i][1];
elevation = eld + (azimuth - azd) * (elf - eld) / (azf - azd);
}
}
return elevation;
}
/** Checking and ordering the azimuth-elevation tabulation.
* @param azimelev azimuth-elevation tabulation to be checked and ordered
* @return ordered azimuth-elevation tabulation ordered
*/
private static double[][] checkMask(final double[][] azimelev) {
// Copy of the given mask
final double[][] mask = new double[azimelev.length + 2][azimelev[0].length];
for (int i = 0; i < azimelev.length; i++) {
System.arraycopy(azimelev[i], 0, mask[i + 1], 0, azimelev[i].length);
// Reducing azimuth between 0 and 2*Pi
mask[i + 1][0] = MathUtils.normalizeAngle(mask[i + 1][0], FastMath.PI);
}
// Sorting the mask with respect to azimuth
Arrays.sort(mask, 1, mask.length - 1, new Comparator() {
public int compare(final double[] d1, final double[] d2) {
return Double.compare(d1[0], d2[0]);
}
});
// Extending the mask in order to cover [0, 2PI] in azimuth
mask[0][0] = mask[mask.length - 2][0] - MathUtils.TWO_PI;
mask[0][1] = mask[mask.length - 2][1];
mask[mask.length - 1][0] = mask[1][0] + MathUtils.TWO_PI;
mask[mask.length - 1][1] = mask[1][1];
// Checking the sorted mask: same azimuth modulo 2PI must have same elevation
for (int i = 1; i < mask.length; i++) {
if (Double.compare(mask[i - 1][0], mask[i][0]) == 0) {
if (Double.compare(mask[i - 1][1], mask[i][1]) != 0) {
throw new OrekitIllegalArgumentException(OrekitMessages.UNEXPECTED_TWO_ELEVATION_VALUES_FOR_ONE_AZIMUTH,
mask[i - 1][1], mask[i][1], mask[i][0]);
}
}
}
return mask;
}
}