Class: Haversine

Inherits:
Object
  • Object
show all
Defined in:
lib/haversine.rb

Overview

PI = 3.1415926535

Defined Under Namespace

Classes: Distance

Constant Summary collapse

RAD_PER_DEG =

PI/180

0.017453293
Rmiles =

the great circle distance d will be in whatever units R is in

3956
Rkm =

radius of the great circle in miles

6371
Rfeet =

radius in kilometers…some algorithms use 6367

Rmiles * 5282
Rmeters =

radius in feet

Rkm * 1000

Class Method Summary collapse

Class Method Details

.distance(lat1, lon1, lat2, lon2) ⇒ Object

given two lat/lon points, compute the distance between the two points using the haversine formula

the result will be a Hash of distances which are key'd by 'mi','km','ft', and 'm'



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# File 'lib/haversine.rb', line 80

def self.distance( lat1, lon1, lat2, lon2 ) 
  dlon = lon2 - lon1
  dlat = lat2 - lat1

  dlon_rad = dlon * RAD_PER_DEG
  dlat_rad = dlat * RAD_PER_DEG

  lat1_rad = lat1 * RAD_PER_DEG
  lon1_rad = lon1 * RAD_PER_DEG

  lat2_rad = lat2 * RAD_PER_DEG
  lon2_rad = lon2 * RAD_PER_DEG

  # puts "dlon: #{dlon}, dlon_rad: #{dlon_rad}, dlat: #{dlat}, dlat_rad: #{dlat_rad}"

  a = (Math.sin(dlat_rad/2))**2 + Math.cos(lat1_rad) * Math.cos(lat2_rad) * (Math.sin(dlon_rad/2))**2
  c = 2 * Math.atan2( Math.sqrt(a), Math.sqrt(1-a))

  dMi = Rmiles * c          # delta between the two points in miles
  dKm = Rkm * c             # delta in kilometers
  dFeet = Rfeet * c         # delta in feet
  dMeters = Rmeters * c     # delta in meters

  distances[:miles] = Distance.in_miles dMi
  distances[:km] = Distance.in_km dKm
  distances[:feet] = Distance.in_feet dFeet
  distances[:meters] = Distance.in_meters dMeters
  distances
end

.distances ⇒ Object 



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# File 'lib/haversine.rb', line 73

def self.distances     
  @distances ||= Hash.new   
end