Class: Breasal::EastingNorthing

Inherits:
Object
  • Object
show all
Includes:
Utils
Defined in:
lib/breasal/easting_northing.rb

Instance Method Summary collapse

Methods included from Utils

#cos_pow_2, #deg_to_rad, #rad_to_deg, #sec, #sin_pow_2, #tan_pow_2

Constructor Details

#initialize(options) ⇒ EastingNorthing

Returns a new instance of EastingNorthing.



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# File 'lib/breasal/easting_northing.rb', line 7

def initialize(options)
  @easting = options[:easting]
  @northing = options[:northing]
  @type = options[:type] || :gb
end

Instance Method Details

#to_latlng(easting, northing, type = :gb) ⇒ Object

Takes OSGB36 or TM75 (Irish national grid) Easting/Northing coords and returns Latitude and Longitude in either OSGB36 or TM75 format



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# File 'lib/breasal/easting_northing.rb', line 23

def to_latlng(easting, northing, type = :gb)

  if type == :ie
     @OSGB_F0  = 1.000035
     @N0       = 250000.0
     @E0       = 200000.0
     @phi0     = deg_to_rad(53.5)
     @lambda0  = deg_to_rad(-8.0)
     @a        = 6377340.189
     @b        = 6356034.447
   else
     @OSGB_F0  = 0.9996012717
     @N0       = -100000.0
     @E0       = 400000.0
     @phi0     = deg_to_rad(49.0)
     @lambda0  = deg_to_rad(-2.0)
     @a        = 6377563.396
     @b        = 6356256.909
   end 

   @eSquared = ((@a * @a) - (@b * @b)) / (@a * @a)
   @phi      = 0.0
   @lambda   = 0.0
   @E        = easting
   @N        = northing
   @n        = (@a - @b) / (@a + @b)
   @M        = 0.0
   @phiPrime = ((@N - @N0) / (@a * @OSGB_F0)) + @phi0

   begin

     @M =
       (@b * @OSGB_F0)\
         * (((1 + @n + ((5.0 / 4.0) * @n * @n) + ((5.0 / 4.0) * @n * @n * @n))\
           * (@phiPrime - @phi0))\
           - (((3 * @n) + (3 * @n * @n) + ((21.0 / 8.0) * @n * @n * @n))\
             * Math.sin(@phiPrime - @phi0)\
             * Math.cos(@phiPrime + @phi0))\
           + ((((15.0 / 8.0) * @n * @n) + ((15.0 / 8.0) * @n * @n * @n))\
             * Math.sin(2.0 * (@phiPrime - @phi0))\
             * Math.cos(2.0 * (@phiPrime + @phi0)))\
           - (((35.0 / 24.0) * @n * @n * @n)\
             * Math.sin(3.0 * (@phiPrime - @phi0))\
             * Math.cos(3.0 * (@phiPrime + @phi0))))

     @phiPrime += (@N - @N0 - @M) / (@a * @OSGB_F0)

   end while ((@N - @N0 - @M) >= 0.001)

   @v = @a * @OSGB_F0 * ((1.0 - @eSquared * sin_pow_2(@phiPrime)) ** -0.5)
   @rho =
     @a\
       * @OSGB_F0\
       * (1.0 - @eSquared)\
       * ((1.0 - @eSquared * sin_pow_2(@phiPrime)) ** -1.5)
   @etaSquared = (@v / @rho) - 1.0
   @VII = Math.tan(@phiPrime) / (2 * @rho * @v)
   @VIII =
     (Math.tan(@phiPrime) / (24.0 * @rho * (@v ** 3.0)))\
       * (5.0\
         + (3.0 * tan_pow_2(@phiPrime))\
         + @etaSquared\
         - (9.0 * tan_pow_2(@phiPrime) * @etaSquared))
   @IX =
     (Math.tan(@phiPrime) / (720.0 * @rho * (@v ** 5.0)))\
       * (61.0\
         + (90.0 * tan_pow_2(@phiPrime))\
         + (45.0 * tan_pow_2(@phiPrime) * tan_pow_2(@phiPrime)))
   @X = sec(@phiPrime) / @v
   @XI =
     (sec(@phiPrime) / (6.0 * @v * @v * @v))\
       * ((@v / @rho) + (2 * tan_pow_2(@phiPrime)))
   @XII =
     (sec(@phiPrime) / (120.0 * (@v ** 5.0)))\
       * (5.0\
         + (28.0 * tan_pow_2(@phiPrime))\
         + (24.0 * tan_pow_2(@phiPrime) * tan_pow_2(@phiPrime)))
   @XIIA =
     (sec(@phiPrime) / (5040.0 * (@v ** 7.0)))\
       * (61.0\
         + (662.0 * tan_pow_2(@phiPrime))\
         + (1320.0 * tan_pow_2(@phiPrime) * tan_pow_2(@phiPrime))\
         + (720.0\
           * tan_pow_2(@phiPrime)\
           * tan_pow_2(@phiPrime)\
           * tan_pow_2(@phiPrime)))
   @phi =
     @phiPrime\
       - (@VII * ((@E - @E0) ** 2.0))\
       + (@VIII * ((@E - @E0) ** 4.0))\
       - (@IX * ((@E - @E0) ** 6.0))
   @lambda =
     @lambda0\
       + (@X * (@E - @E0))\
       - (@XI * ((@E - @E0) ** 3.0))\
       + (@XII * ((@E - @E0) ** 5.0))\
       - (@XIIA * ((@E - @E0) ** 7.0))

  { :latitude => rad_to_deg(@phi), :longitude => rad_to_deg(@lambda) }

end

#to_wgs84 ⇒ Object

Takes OSGB36 or TM75 (Irish national grid) Easting/Northing coords and returns WGS84 Latitude and Longitude



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# File 'lib/breasal/easting_northing.rb', line 15

def to_wgs84
  ll = to_latlng(@easting, @northing, @type)
  lat_lng = LatLng.new(latitude: ll[:latitude], longitude: ll[:longitude], type: @type)
  lat_lng.to_WGS84
end