Java tutorial
/* Copyright 2013 Applied Defense Solutions, Inc. * Licensed to CS Communication & Systmes (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.apache.commons.math3.util.FastMath; import org.apache.commons.math3.util.MathUtils; import org.orekit.errors.OrekitIllegalArgumentException; import org.orekit.errors.OrekitMessages; /** * Class for modeling the ground elevation values around a given point. * <p> * 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) */ 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<double[]>() { 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; } }