module Etrstm35fin

# File lib/etrstm35fin.rb, line 53
def self.to_degrees(val)
  (val  * 180.0) / Math::PI
end

# File lib/etrstm35fin.rb, line 57
def self.to_radians(degree)
  degree * (Math::PI / 180)
end

# File lib/etrstm35fin.rb, line 13
def self.to_wgs84(north_coordinate, east_coordinate)
  central_meridian = to_radians(CENTRAL_MERIDIAN)

  n = FLATTENING / (2.0 - FLATTENING)
  a1 = WGS84_MAJOR / (1.0 + n) * (1.0 + (n**2.0) / 4.0 + (n**4.0) / 64.0)
  e = Math.sqrt(2.0 * FLATTENING - (FLATTENING**2.0))
  h1 = 1.0 / 2.0 * n - 2.0 / 3.0 * (n**2.0) + 37.0/96.0 * (n**3.0) - 1.0/360.0 * (n**4.0)
  h2 = 1.0 / 48.0 * (n**2.0) + 1.0/15.0 * (n**3.0) - 437.0/1440.0 * (n**4.0)
  h3 = 17.0 / 480.0 * (n**3.0) - 37.0 / 840.0 * (n**4.0)
  h4 = 4397.0 / 161280.0 * (n**4.0)

  ee = north_coordinate / (a1 * SCALE_FACTOR)
  nn = (east_coordinate - FALSE_EASTING) / (a1 * SCALE_FACTOR)

  e1p = h1 * Math.sin(2.0 * ee) * Math.cosh(2.0 * nn)
  e2p = h2 * Math.sin(4.0 * ee) * Math.cosh(4.0 * nn)
  e3p = h3 * Math.sin(6.0 * ee) * Math.cosh(6.0 * nn)
  e4p = h4 * Math.sin(8.0 * ee) * Math.cosh(8.0 * nn)

  nn1p = h1 * Math.cos(2.0 * ee) * Math.sinh(2.0 * nn)
  nn2p = h2 * Math.cos(4.0 * ee) * Math.sinh(4.0 * nn)
  nn3p = h3 * Math.cos(6.0 * ee) * Math.sinh(6.0 * nn)
  nn4p = h4 * Math.cos(8.0 * ee) * Math.sinh(8.0 * nn)

  ep = ee - e1p - e2p - e3p - e4p

  nnp = nn - nn1p - nn2p - nn3p - nn4p
  be = Math.asin(Math.sin(ep) / Math.cosh(nnp))

  q = CMath.asinh(Math.tan(be))
  qp = q + e * CMath.atanh(e * Math.tanh(q))
  qp = q + e * CMath.atanh(e * Math.tanh(qp))
  qp = q + e * CMath.atanh(e * Math.tanh(qp))
  qp = q + e * CMath.atanh(e * Math.tanh(qp))

  lat = to_degrees(Math.atan(Math.sinh(qp)))
  lon = to_degrees(central_meridian + Math.asin(Math.tanh(nnp) / Math.cos(be)))
  [lat, lon]
end