io_import_dxf/transverse_mercator.py

   1 # SPDX-License-Identifier: GPL-2.0-or-later
   2
   3 from math import sin, cos, atan, atanh, radians, tan, sinh, asin, cosh, degrees
   4
   5 # see conversion formulas at
   6 # http://en.wikipedia.org/wiki/Transverse_Mercator_projection
   7 # http://mathworld.wolfram.com/MercatorProjection.html
   8
   9
  10 class TransverseMercator:
  11     radius = 6378137
  12
  13     def __init__(self, lat=0, lon=0):
  14         self.lat = lat  # in degrees
  15         self.lon = lon  # in degrees
  16         self.lat_rad = radians(self.lat)
  17         self.lon_rad = radians(self.lon)
  18
  19     def fromGeographic(self, lat, lon):
  20         lat_rad = radians(lat)
  21         lon_rad = radians(lon)
  22         B = cos(lat_rad) * sin(lon_rad - self.lon_rad)
  23         x = self.radius * atanh(B)
  24         y = self.radius * (atan(tan(lat_rad) / cos(lon_rad - self.lon_rad)) - self.lat_rad)
  25         return x, y
  26
  27     def toGeographic(self, x, y):
  28         x /= self.radius
  29         y /= self.radius
  30         D = y + self.lat_rad
  31         lon = atan(sinh(x) / cos(D))
  32         lat = asin(sin(D) / cosh(x))
  33
  34         lon = self.lon + degrees(lon)
  35         lat = degrees(lat)
  36         return lat, lon