Class: Drifter::Distance::Haversine

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

Constant Summary collapse

EarthRadiusInMiles = 
3956
EarthRadiusInKms = 
6371
RAD_PER_DEG =

PI/180

0.017453293

Class Method Summary collapse

Class Method Details

.between(point1, point2, options = {}) ⇒ Object

this method is from Landon Cox’s haversine.rb (GNU Affero GPL v3): www.esawdust.com/blog/gps/files/HaversineFormulaInRuby.html: www.esawdust.com (Landon Cox) www.esawdust.com/blog/businesscard/businesscard.html



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# File 'lib/drifter/distance/haversine.rb', line 14

def self.between(point1, point2, options={})
  lat1, lon1 = Drifter.extract_latlng!(point1)
  lat2, lon2 = Drifter.extract_latlng!(point2)

  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

  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))

  units = options.delete(:units) || Drifter.default_units
  return EarthRadiusInKms * c if units == :km
  return EarthRadiusInMiles * c
end

.to_mysql(options) ⇒ Object

postgresql code seems to work fine fo sql



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# File 'lib/drifter/distance/haversine.rb', line 63

def self.to_mysql(options)
  to_postgresql(options)
end

.to_postgresql(options) ⇒ Object

haversine sql based on code.google.com/apis/maps/articles/phpsqlsearch.html you will need to add ‘select’ and ‘AS distance’ if required



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# File 'lib/drifter/distance/haversine.rb', line 41

def self.to_postgresql(options)
  origin = options[:origin]
  lat, lng = Drifter.extract_latlng!(origin)
  lat_column = options[:lat_column] || :lat
  lng_column = options[:lng_column] || :lng
  units = options[:units] || Drifter.default_units
  multiplier = EarthRadiusInMiles
  multiplier = EarthRadiusInKms if units == :km

  postgres = "    \#{multiplier} * ACOS(\n      COS( RADIANS(\#{lat}) ) *\n      COS( RADIANS( \#{lat_column} ) ) *\n      COS( RADIANS( \#{lng_column} ) -\n      RADIANS(\#{lng}) ) +\n      SIN( RADIANS(\#{lat}) ) *\n      SIN( RADIANS( \#{lat_column} ) )\n    )\n  EOS\nend\n"