Location queries for a model

ajturner (Andrew Turner) — Wed, 12 Apr 2006 05:46:45 GMT

// These are class functions which are useful for finding locations in a database
// when PostGIS is not available (when using MySQL for example)



def self.deg2rad(deg)

	(deg * Math::PI / 180)

end



def self.rad2deg(rad)

	(rad * 180 / Math::PI)

end



def self.acos(rad)

	Math.atan2(Math.sqrt(1 - rad**2), rad)

end



def self.distance_in_miles(loc1, loc2)

	lat1 = loc1.latitude

	lon1 = loc1.longitude

	lat2 = loc2.latitude

	lon2 = loc2.longitude

	theta = lon1 - lon2

	

	dist = Math.sin(self.deg2rad(lat1)) * Math.sin(deg2rad(lat2)) 

		+ Math.cos(self.deg2rad(lat1)) * Math.cos(self.deg2rad(lat2)) * Math.cos(deg2rad(theta))

	

	dist = self.rad2deg(self.acos(dist))

	

	(dist * 60 * 1.1515).round #distance in miles

end



def miles_to(location)

	Location.distance_in_miles(self, location)

end



def self.locationArea(location, miles)

	radius = miles.to_f

	latR = radius / ((6076 / 5280) * 60)

	lonR = radius / (((Math.cos(location.latitude * Math::PI / 180) * 6076) / 5280) * 60)

	

	{

		:min_latitude => location.latitude - latR,

		:min_longitude => location.longitude - lonR,

		:max_latitude => location.latitude + latR,

		:max_longitude => location.longitude + lonR

	}

end



def self.location_ids_in_range(location, miles)

	la = Location.locationArea(location, miles)

	Location.find(:all,

		:select => "locations.id",

		:conditions => ["locations.latitude <= ? and locations.latitude >= ? " + \

			" AND locations.longitude >= ? and locations.longitude <= ?",

			la[:max_latitude], la[:min_latitude], la[:min_longitude], la[:max_longitude]

		]

	).collect { |l| l.id }

end



def self.locations_in_range(location, miles)

	la = Location.locationArea(location, miles)

	Location.find(:all,

		:conditions => ["locations.latitude <= ? and locations.latitude >= ? " + \

			" AND locations.longitude >= ? and locations.longitude <= ?",

			la[:max_latitude], la[:min_latitude], la[:min_longitude], la[:max_longitude]

		]

	)

end

DZone Snippets: rails code

Location queries for a model