X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=altosui%2FAltosGreatCircle.java;fp=altosui%2FAltosGreatCircle.java;h=fb1b6ab3e129fa3781fcafe95a0e46a325cc083f;hb=28d621c5885953afe3b7435e582b80b75314506e;hp=0000000000000000000000000000000000000000;hpb=6d0098e497ee2d9a1d1113bf3fb907dd48bdcf80;p=fw%2Faltos

diff --git a/altosui/AltosGreatCircle.java 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;
+	}
+}