Merge branch 'buttonbox' of git://git.gag.com/fw/altos into buttonbox

[fw/altos] / altosui / AltosGreatCircle.java

diff --git a/altosui/AltosGreatCircle.java b/altosui/AltosGreatCircle.java
new file mode 100644 (file)
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+++ b/altosui/AltosGreatCircle.java
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+/*
+ * Copyright © 2010 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+package altosui;
+
+import java.lang.Math;
+
+public class AltosGreatCircle {
+       double  distance;
+       double  bearing;
+
+       double sqr(double a) { return a * a; }
+
+       static final double rad = Math.PI / 180;
+       static final double earth_radius = 6371.2 * 1000;       /* in meters */
+
+    static int BEARING_LONG = 0;
+    static int BEARING_SHORT = 1;
+    static int BEARING_VOICE = 2;
+    String bearing_words(int length) {
+        String [][] bearing_string = {
+          {
+            "North", "North North East", "North East", "East North East",
+            "East", "East South East", "South East", "South South East",
+            "South", "South South West", "South West", "West South West",
+            "West", "West North West", "North West", "North North West"
+          }, {
+            "N", "NNE", "NE", "ENE",
+            "E", "ESE", "SE", "SSE",
+            "S", "SSW", "SW", "WSW",
+            "W", "WNW", "NW", "NNW"
+          }, {
+            "north", "nor nor east", "north east", "east nor east",
+            "east", "east sow east", "south east", "sow sow east",
+            "south", "sow sow west", "south west", "west sow west",
+            "west", "west nor west", "north west", "nor nor west "
+          }
+        };
+        return bearing_string[length][(int)((bearing / 90 * 8 + 1) / 2)%16];
+    }
+
+       public AltosGreatCircle (double start_lat, double start_lon,
+                                double end_lat, double end_lon)
+       {
+               double lat1 = rad * start_lat;
+               double lon1 = rad * -start_lon;
+               double lat2 = rad * end_lat;
+               double lon2 = rad * -end_lon;
+
+               double d_lon = lon2 - lon1;
+
+               /* From http://en.wikipedia.org/wiki/Great-circle_distance */
+               double vdn = Math.sqrt(sqr(Math.cos(lat2) * Math.sin(d_lon)) +
+                                      sqr(Math.cos(lat1) * Math.sin(lat2) -
+                                          Math.sin(lat1) * Math.cos(lat2) * Math.cos(d_lon)));
+               double vdd = Math.sin(lat1) * Math.sin(lat2) + Math.cos(lat1) * Math.cos(lat2) * Math.cos(d_lon);
+               double d = Math.atan2(vdn,vdd);
+               double course;
+
+               if (Math.cos(lat1) < 1e-20) {
+                       if (lat1 > 0)
+                               course = Math.PI;
+                       else
+                               course = -Math.PI;
+               } else {
+                       if (d < 1e-10)
+                               course = 0;
+                       else
+                               course = Math.acos((Math.sin(lat2)-Math.sin(lat1)*Math.cos(d)) /
+                                                  (Math.sin(d)*Math.cos(lat1)));
+                       if (Math.sin(lon2-lon1) > 0)
+                               course = 2 * Math.PI-course;
+               }
+               distance = d * earth_radius;
+               bearing = course * 180/Math.PI;
+       }
+
+       public AltosGreatCircle(AltosGPS start, AltosGPS end) {
+               this(start.lat, start.lon, end.lat, end.lon);
+       }
+
+       public AltosGreatCircle() {
+               distance = 0;
+               bearing = 0;
+       }
+}