From e8c17f28243523b5f9c0e21e911cc4b2ff030b2d Mon Sep 17 00:00:00 2001
From: Mat Ellis <mat@tecnh.com>
Date: Fri, 18 Mar 2011 14:50:04 -0700
Subject: [PATCH] Adds methods for calculating the bearing between two points
and for converting that bearing into a compass point, e.g. North or South
West. If you want fewer or additional compass points (e.g. South By South
West, or just NESW) provide a second parameter containing your array of
points, e.g.
Geocoder::Calculations::compass_point(90,['north','east','south','west'])
---
lib/geocoder/calculations.rb | 30 ++++++++++++++++++++++++++++++
test/geocoder_test.rb | 13 +++++++++++++
2 files changed, 43 insertions(+)
diff --git a/lib/geocoder/calculations.rb b/lib/geocoder/calculations.rb
index 35136960..b99e35f0 100644
--- a/lib/geocoder/calculations.rb
+++ b/lib/geocoder/calculations.rb
@@ -88,5 +88,35 @@ module Geocoder
def km_in_mi
0.621371192
end
+
+ ##
+ # Calculate bearing between two sets of co-ordinates
+ #
+ def bearing_between(lat1, lon1, lat2, lon2, options = {})
+ # Math courtesy of http://www.movable-type.co.uk/scripts/latlong.html
+ dlon = to_radians((lon1 - lon2).abs)
+
+ y = Math.sin(dlon) * Math.cos(lat2)
+ x = Math.cos(lat1) * Math.sin(lat2) - Math.sin(lat1) * Math.cos(lat2) * Math.cos(dlon)
+ brng = Math.atan2(x,y)
+ (to_degrees(brng) + 360) % 360
+ end
+
+ # If you want more or fewer points simply override Geocoder::Calculations.COMPASS_POINTS with your own array
+ COMPASS_POINTS = [{:name => "North", :abbr => "N"},
+ {:name => "North East", :abbr => "NE"},
+ {:name => "East", :abbr => "E"},
+ {:name => "South East", :abbr => "SE"},
+ {:name => "South", :abbr => "S"},
+ {:name => "South West", :abbr => "SW"},
+ {:name => "West", :abbr => "W"},
+ {:name => "North West", :abbr => "NW"}]
+
+ ##
+ # Compass direction (North, South, etc.) between two sets of co-ordinates
+ def compass_point(bearing, points = COMPASS_POINTS)
+ seg_size = 360/points.length
+ points[((bearing + (seg_size/2) ) % 360) / seg_size]
+ end
end
end
diff --git a/test/geocoder_test.rb b/test/geocoder_test.rb
index 2d29fc10..458b59ee 100644
--- a/test/geocoder_test.rb
+++ b/test/geocoder_test.rb
@@ -23,6 +23,19 @@ class GeocoderTest < Test::Unit::TestCase
assert_equal 69, Geocoder::Calculations.distance_between(0,0, 0,1).round
end
+ def test_distance_between
+ hash_north = {:name => "North", :abbr => "N"}
+ hash_south = {:name => "South", :abbr => "S"}
+ hash_nw = {:name => "North West", :abbr => "NW"}
+ assert_equal hash_north, Geocoder::Calculations.compass_point(0)
+ assert_equal hash_north, Geocoder::Calculations.compass_point(360)
+ assert_equal hash_north, Geocoder::Calculations.compass_point(361)
+ assert_equal hash_north, Geocoder::Calculations.compass_point(-22)
+ assert_equal hash_nw, Geocoder::Calculations.compass_point(-23)
+ assert_equal hash_south, Geocoder::Calculations.compass_point(180)
+ assert_equal hash_south, Geocoder::Calculations.compass_point(181)
+ end
+
def test_geographic_center_with_arrays
assert_equal [0.0, 0.5],
Geocoder::Calculations.geographic_center([[0,0], [0,1]])
--
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