From 9f879b8dc14393c8ac03882c2d8a1a5f9e2684a4 Mon Sep 17 00:00:00 2001
From: Alex Reisner <alex@alexreisner.com>
Date: Thu, 24 Mar 2011 13:03:49 -0400
Subject: [PATCH] Fix bug in dlon calculation.
This was yielding incorrect bearing calculations (east and west were
treated as the same direction).
---
lib/geocoder/calculations.rb | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/lib/geocoder/calculations.rb b/lib/geocoder/calculations.rb
index ac1952a9..5a994406 100644
--- a/lib/geocoder/calculations.rb
+++ b/lib/geocoder/calculations.rb
@@ -24,9 +24,9 @@ module Geocoder
# convert degrees to radians
lat1, lon1, lat2, lon2 = to_radians(lat1, lon1, lat2, lon2)
- # compute distances
- dlat = (lat1 - lat2).abs
- dlon = (lon1 - lon2).abs
+ # compute deltas
+ dlat = lat2 - lat1
+ dlon = lon2 - lon1
a = (Math.sin(dlat / 2))**2 + Math.cos(lat1) *
(Math.sin(dlon / 2))**2 * Math.cos(lat2)
@@ -41,7 +41,13 @@ module Geocoder
# Based on: http://www.movable-type.co.uk/scripts/latlong.html
#
def bearing_between(lat1, lon1, lat2, lon2)
- dlon = to_radians((lon1 - lon2).abs)
+
+ # convert degrees to radians
+ lat1, lon1, lat2, lon2 = to_radians(lat1, lon1, lat2, lon2)
+
+ # compute deltas
+ dlon = lon2 - lon1
+
y = Math.sin(dlon) * Math.cos(lat2)
x = Math.cos(lat1) * Math.sin(lat2) - Math.sin(lat1) *
Math.cos(lat2) * Math.cos(dlon)
--
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