Calculating distance between two points in Ruby with the Haversine formula

I recently needed to calculate the distance between two points (lat/long) in Ruby (reading a .gpx file, and finding the distance between each point).

After a quick search on stackoverflow.com I found the following post http://stackoverflow.com/questions/569980/how-to-calculate-distance-from-a-gpx-file.

Below is my Ruby version of the formula shown in the second post:

	def haversine(lat1, long1, lat2, long2)
	dtor = Math::PI/180
	r = 6378.14*1000
	rlat1 = lat1 * dtor
	rlong1 = long1 * dtor
	rlat2 = lat2 * dtor
	rlong2 = long2 * dtor
	dlon = rlong1 - rlong2
	dlat = rlat1 - rlat2
	a = power(Math::sin(dlat/2), 2) + Math::cos(rlat1) * Math::cos(rlat2) * power(Math::sin(dlon/2), 2)
	c = 2 * Math::atan2(Math::sqrt(a), Math::sqrt(1-a))
	d = r * c
	return d
	end

view raw gistfile1.rb hosted with ❤ by GitHub

This will calculate in meters. To get KM, remove "*1000" on line 3. To get miles, change line 3 to "r = 3959". I'll post the whole GPX parse code in a few days.