From: Keith Packard <keithp@keithp.com>
Date: Sun, 12 Jul 2015 02:13:37 +0000 (-0700)
Subject: altoslib: Convert longitude from distance in AltosMapTransform
X-Git-Tag: 1.6.0.4~12
X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=commitdiff_plain;h=afa37e4667ace42c1f43b01b613e639772cfeb75

altoslib: Convert longitude from distance in AltosMapTransform

This computes the longitude cooresponding to a specific distance at a
specific latitude.

Signed-off-by: Keith Packard <keithp@keithp.com>
---

diff --git a/altoslib/AltosMapTransform.java b/altoslib/AltosMapTransform.java
index 11ed4eb9..7615c83b 100644
--- a/altoslib/AltosMapTransform.java
+++ b/altoslib/AltosMapTransform.java
@@ -117,4 +117,12 @@ public class AltosMapTransform {
 		offset_x = centre_pt.x - width / 2.0;
 		offset_y = centre_pt.y - height / 2.0;
 	}
+
+	public static double lon_from_distance(double lat, double distance) {
+		double c = AltosGreatCircle.earth_radius * Math.cos(lat * Math.PI / 180) * 2 * Math.PI;
+
+		if (c < 10)
+			return 0;
+		return distance/c * 360.0;
+	}
 }