gistfile1.txt

#!/usr/bin/env ruby

require 'bigdecimal'


DEG_TO_RAD = 0.017453292519943295769236907684886
EARTH_RADIUS_IN_METERS = 6372797.560856

def approximateDistance   lat1, lon1, lat2, lon2
  #assert(lat1 != INT_MIN)
  #assert(lon1 != INT_MIN)
  #assert(lat2 != INT_MIN)
  #assert(lon2 != INT_MIN)
  #Earth's quatratic mean radius for WGS-84
  latitudeArc  = (DEG_TO_RAD*(lat1-lat2))/100000.0
  longitudeArc = (DEG_TO_RAD*(lon1-lon2))/100000.0
  latitudeH = Math.sin( latitudeArc * 0.5 )
  latitudeH *= latitudeH
  lontitudeH = Math.sin( longitudeArc * 0.5 )
  lontitudeH *= lontitudeH
  tmp = Math.cos( (DEG_TO_RAD*lat1)/100000.0 ) * Math.cos( (DEG_TO_RAD*lat2)/100000.0 )
  distanceArc =  2.0 * Math.asin( Math.sqrt( latitudeH + tmp * lontitudeH ) )
  EARTH_RADIUS_IN_METERS * distanceArc
end

def simplified lat1, lon1, lat2, lon2
  EARTH_RADIUS_IN_METERS * DEG_TO_RAD * Math.sqrt( (lat2-lat1)*(lat2-lat1) + (lon2-lon1)*(lon2-lon1) ) / 100000.0;
end

#calculate constant for use in distance tests
def ap lat1, lon1, lat2, lon2
  BigDecimal.new("1")/(BigDecimal.new("6372797.560856")*BigDecimal.new("0.017453292519943295769236907684886"));
end

lat1 = 1*100000.0
lon1 = 1*100000.0
lat2  = 1*100000.0
lon2  = 1.0008990679362704*100000.0


puts approximateDistance(lat1,lon1,lat2,lon2)