Contents

module GPX

	# Class is responsible for calculating distance between two geo points (it considers point height)
	class Haversine
		RADIAN_PER_DEGREE = Math::PI/180.0
		EARTH_RADIUS = 6371.00079

		def self.distance(first_point, second_point)
			first_latitude_rad = first_point.latitude.to_f * RADIAN_PER_DEGREE
			second_latitude_rad = second_point.latitude.to_f * RADIAN_PER_DEGREE

			delta_longitude = (second_point.longitude.to_f - first_point.longitude.to_f) * RADIAN_PER_DEGREE
			delta_latitude =  (second_point.latitude.to_f - first_point.latitude.to_f) * RADIAN_PER_DEGREE

			elevation = (first_point.elevation.to_f / 1000.0 - second_point.elevation.to_f / 1000.0).abs

			distance = calculate_distance(first_latitude_rad, second_latitude_rad, delta_latitude, delta_longitude)
			triangulate(EARTH_RADIUS * distance, elevation)
		end

		private
			def self.calculate_distance(first_latitude_rad, second_latitude_rad, delta_latitude, delta_longitude)
				coefficient = (Math::sin(delta_latitude/2.0)**2.0) +
							Math::cos(first_latitude_rad) * Math::cos(second_latitude_rad) * (Math::sin(delta_longitude/2.0)**2.0)

				2.0 * Math::atan2(Math::sqrt(coefficient), Math::sqrt(1.0-coefficient))
			end

			def self.triangulate (distance, height)
				Math::sqrt(distance**2 + height**2)
			end
	end
end

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
gpx_track-0.0.2	lib/gpx/haversine.rb