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   1 /*
   2  * Copyright © 2010 Keith Packard <keithp@keithp.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
  17  */
  18
  19 package org.altusmetrum.altoslib_13;
  20
  21 import java.lang.Math;
  22 import java.io.*;
  23
  24 public class AltosGreatCircle implements Cloneable {
  25         public double   distance;
  26         public double   bearing;
  27         public double   range;
  28         public double   elevation;
  29
  30         double sqr(double a) { return a * a; }
  31
  32         public static final double rad = Math.PI / 180;
  33         public static final double earth_radius = 6371.2 * 1000;        /* in meters */
  34
  35         public static final int BEARING_LONG = AltosConvert.BEARING_LONG;
  36         public static final int BEARING_SHORT = AltosConvert.BEARING_SHORT;
  37         public static final int BEARING_VOICE = AltosConvert.BEARING_VOICE;
  38
  39         public String bearing_words(int length) {
  40                 return AltosConvert.bearing_to_words(length, bearing);
  41         }
  42
  43         public AltosGreatCircle (double start_lat, double start_lon, double start_alt,
  44                                  double end_lat, double end_lon, double end_alt) {
  45                 double lat1 = rad * start_lat;
  46                 double lon1 = rad * -start_lon;
  47                 double lat2 = rad * end_lat;
  48                 double lon2 = rad * -end_lon;
  49
  50                 double d_lon = lon2 - lon1;
  51
  52                 /* From http://en.wikipedia.org/wiki/Great-circle_distance */
  53                 double vdn = Math.sqrt(sqr(Math.cos(lat2) * Math.sin(d_lon)) +
  54                                        sqr(Math.cos(lat1) * Math.sin(lat2) -
  55                                            Math.sin(lat1) * Math.cos(lat2) * Math.cos(d_lon)));
  56                 double vdd = Math.sin(lat1) * Math.sin(lat2) + Math.cos(lat1) * Math.cos(lat2) * Math.cos(d_lon);
  57                 double d = Math.atan2(vdn,vdd);
  58                 double course;
  59
  60                 if (Math.cos(lat1) < 1e-20) {
  61                         if (lat1 > 0)
  62                                 course = Math.PI;
  63                         else
  64                                 course = -Math.PI;
  65                 } else {
  66                         if (d < 1e-10)
  67                                 course = 0;
  68                         else
  69                                 course = Math.acos((Math.sin(lat2)-Math.sin(lat1)*Math.cos(d)) /
  70                                                    (Math.sin(d)*Math.cos(lat1)));
  71                         if (Math.sin(lon2-lon1) > 0)
  72                                 course = 2 * Math.PI-course;
  73                 }
  74                 distance = d * earth_radius;
  75                 if (Double.isNaN(course) || Double.isInfinite(course))
  76                         bearing = 0;
  77                 else
  78                         bearing = course * 180/Math.PI;
  79
  80                 double height_diff = end_alt - start_alt;
  81                 range = Math.sqrt(distance * distance + height_diff * height_diff);
  82                 elevation = Math.atan2(height_diff, distance) * 180 / Math.PI;
  83         }
  84
  85         public AltosGreatCircle clone() {
  86                 AltosGreatCircle n = new AltosGreatCircle();
  87
  88                 n.distance = distance;
  89                 n.bearing = bearing;
  90                 n.range = range;
  91                 n.elevation = elevation;
  92                 return n;
  93         }
  94
  95         public AltosGreatCircle (double start_lat, double start_lon,
  96                                  double end_lat, double end_lon) {
  97                 this(start_lat, start_lon, 0, end_lat, end_lon, 0);
  98         }
  99
 100         public AltosGreatCircle(AltosGPS start, AltosGPS end) {
 101                 this(start.lat, start.lon, start.alt, end.lat, end.lon, end.alt);
 102         }
 103
 104         public AltosGreatCircle() {
 105                 distance = 0;
 106                 bearing = 0;
 107                 range = 0;
 108                 elevation = 0;
 109         }
 110 }