Module: Tillless::Location::InstanceMethods

Defined in:
lib/tillless-core/location.rb

Instance Method Summary collapse

Instance Method Details

#calibrate ⇒ Object

Pre-calculate the various terms of the Great Circle Distance Formula

Tillless::Location::RADIUS_OF_EARTH *                            # Radius of Earth in KM
  acos[
     sin(lat1/57.2958) *                     # term1
     sin(lat2/57.2958) +                     # term2
     cos(lat1/57.2958) *                     # term3
     cos(lat2/57.2958) *                     # term4
     cos(
         lon2/57.2958  -                     # term5
         lon1/57.2958)                       # term6
  ]



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# File 'lib/tillless-core/location.rb', line 186

def calibrate
  self.term1 = Math.sin(self.lat/Tillless::Location::GREAT_CIRCLE_FACTOR)
  self.term2 = Math.sin(self.lat/Tillless::Location::GREAT_CIRCLE_FACTOR)
  self.term3 = Math.cos(self.lat/Tillless::Location::GREAT_CIRCLE_FACTOR)
  self.term4 = Math.cos(self.lat/Tillless::Location::GREAT_CIRCLE_FACTOR)
  self.term5 = self.lon/Tillless::Location::GREAT_CIRCLE_FACTOR
  self.term6 = self.lon/Tillless::Location::GREAT_CIRCLE_FACTOR
  self.calibrated = true
end

#great_circle_distance_from_here_to(otherloc) ⇒ Object

Calculate the great circle distance between this GeoLocation and the specified other location. This uses the formula specified here: www.meridianworlddata.com/Distance-Calculation.asp

The formula used to calculate the Great Circle Distance is:

RADIUS_OF_EARTH * acos[sin(lat1/57.2958) * sin(lat2/57.2958) + cos(lat1/57.2958) * cos(lat2/57.2958) * cos(lon2/57.2958 - lon1/57.2958)]

Where: lat1/lon1 is the lat and lon of this Location, and lat2/lon2 is the lat and lon of the other location.

:otherloc location to compare with return great circle distance from here to otherloc raises LocationCalibrationException if either self or otherloc are not calibrated

Raises:



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# File 'lib/tillless-core/location.rb', line 210

def great_circle_distance_from_here_to(otherloc)
  raise Tillless::Location::LocationCalibrationException if ! (self.calibrated and otherloc.calibrated)
  stage1 = self.term1 * otherloc.term2 +
           self.term3 * otherloc.term4 *
           Math.cos(self.term5 - otherloc.term6)
  # fix floating point roudning error that manifests in ActiveRecord and Postgres
  stage1 = stage1.round if stage1 < -1 or stage1 > 1
  Tillless::Location::RADIUS_OF_EARTH * Math.acos(stage1)
end

#nearby?(otherloc, min_distance = Tillless::Location::MIN_DISTANCE_FOR_NEARBY_IN_KM) ⇒ Boolean

Test to see if the specified location is near this one, where ‘near’ means within 100 meters.

:otherloc location to check :min_distance minimum distance for which to be considered ‘nearby’, default = Tillless::Location::MIN_DISTANCE_FOR_NEARBY_IN_KM return true if the specified location is near this one raises LocationCalibrationException if either self or otherloc are not calibrated

Returns:

  • (Boolean)

Raises:



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# File 'lib/tillless-core/location.rb', line 228

def nearby?(otherloc, min_distance = Tillless::Location::MIN_DISTANCE_FOR_NEARBY_IN_KM)
  raise Tillless::Location::LocationCalibrationException if ! (self.calibrated and otherloc.calibrated)
  ( (great_circle_distance_from_here_to(otherloc) - min_distance) <= 0.0)
end

#set_and_calibrate(_lat, _lon) ⇒ Object

Set both lat and lon and recalibrate in the one go



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# File 'lib/tillless-core/location.rb', line 168

def set_and_calibrate(_lat, _lon)
  self.lat = _lat
  self.lon = _lon
  calibrate
end