Converts coordinates from the 1903 Swiss national grid system to WGS-84.

def ConvertCH1903(x, y):
  "Converts coordinates from the 1903 Swiss national grid system to WGS-84."
  yb = (x - 600000.0) / 1e6;
  xb = (y - 200000.0) / 1e6;
  lam = 2.6779094 \
     + 4.728982 * yb \
     + 0.791484 * yb * xb \
     + 0.1306 * yb * xb * xb \
     - 0.0436 * yb * yb * yb
  phi = 16.9023892 \
     + 3.238372 * xb \
     - 0.270978 * yb * yb \
     - 0.002582 * xb * xb \
     - 0.0447 * yb * yb * xb \
     - 0.0140 * xb * xb * xb
  return (phi * 100.0 / 36.0, lam * 100.0 / 36.0)