Class: ProximityHash

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

Constant Summary collapse

MIN_PRECISION = 
1
MAX_PRECISION = 
12
EARTH_RADIUS = 
6371000

Instance Method Summary collapse

Constructor Details

#initialize(latitude, longitude, radius, precision) ⇒ ProximityHash

Returns a new instance of ProximityHash.



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# File 'lib/proximityhash.rb', line 11

def initialize(latitude, longitude, radius, precision)
  @centre = [ latitude, longitude ]
  @radius = radius
  @precision = precision
  if ((precision > MAX_PRECISION) or (precision < MIN_PRECISION))
    raise 'Precision out bounds'
  end
end

Instance Method Details

#calculate ⇒ Object 



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# File 'lib/proximityhash.rb', line 20

def calculate
  x = 0.0
  y = 0.0

  points = []
  geohashes = {}

  grid_width = [ 5009400.0, 1252300.0, 156500.0, 39100.0, 4900.0, 1200.0, 152.9, 38.2, 4.8, 1.2, 0.149, 0.0370 ]
  grid_height = [ 4992600.0, 624100.0, 156000.0, 19500.0, 4900.0, 609.4, 152.4, 19.0, 4.8, 0.595, 0.149, 0.0199 ]

  height = (grid_height[@precision - 1]) / 2.0
  width = (grid_width[@precision - 1]) / 2.0

  latitude = @centre[0]
  longitude = @centre[1]

  lat_moves = (@radius / height).ceil
  lon_moves = (@radius / width).ceil

  (0 .. lat_moves).each do |i|

    temp_lat = y + (height * i)

    (0..lon_moves).each do |j|

      temp_lon = x + (width * j)

      if within_radius(temp_lat, temp_lon, y, x) == true

        x_cen, y_cen = get_centre(temp_lat, temp_lon, height, width)
        lat, lon = convert_to_latlon(y_cen, x_cen, latitude, longitude)
        points += [[lat, lon]]
        lat, lon = convert_to_latlon(-y_cen, x_cen, latitude, longitude)
        points += [[lat, lon]]
        lat, lon = convert_to_latlon(y_cen, -x_cen, latitude, longitude)
        points += [[lat, lon]]
        lat, lon = convert_to_latlon(-y_cen, -x_cen, latitude, longitude)
        points += [[lat, lon]]
      end

    end

  end

  points.each do |point|
    geohash = GeoHash.encode(point[0], point[1], @precision)
    geohashes[geohash] = Haversine.distance(point, @centre).to_meters
  end

  geohashes.sort_by { |key, value| value }.to_h
end