extlib/leaflet/src/geo/projection/Projection.Mercator.js

   1
   2 L.Projection.Mercator = {
   3         MAX_LATITUDE: 85.0840591556,
   4
   5         R_MINOR: 6356752.3142,
   6         R_MAJOR: 6378137,
   7
   8         project: function(/*LatLng*/ latlng) /*-> Point*/ {
   9                 var d = L.LatLng.DEG_TO_RAD,
  10                         max = this.MAX_LATITUDE,
  11                         lat = Math.max(Math.min(max, latlng.lat), -max),
  12                         r = this.R_MAJOR,
  13                         x = latlng.lng * d * r,
  14                         y = lat * d,
  15                         tmp = this.R_MINOR / r,
  16                         eccent = Math.sqrt(1.0 - tmp * tmp),
  17                         con = eccent * Math.sin(y);
  18
  19                 con = Math.pow((1 - con)/(1 + con), eccent * 0.5);
  20
  21                 var ts = Math.tan(0.5 * ((Math.PI * 0.5) - y)) / con;
  22                 y = -r * Math.log(ts);
  23
  24                 return new L.Point(x, y);
  25         },
  26
  27         unproject: function(/*Point*/ point, /*Boolean*/ unbounded) /*-> LatLng*/ {
  28                 var d = L.LatLng.RAD_TO_DEG,
  29                         r = this.R_MAJOR,
  30                         lng = point.x * d / r,
  31                         tmp = this.R_MINOR / r,
  32                         eccent = Math.sqrt(1 - (tmp * tmp)),
  33                         ts = Math.exp(- point.y / r),
  34                         phi = Math.PI/2 - 2 * Math.atan(ts),
  35                         numIter = 15,
  36                         tol = 1e-7,
  37                         i = numIter,
  38                         dphi = 0.1,
  39                         con;
  40
  41                 while ((Math.abs(dphi) > tol) && (--i > 0)) {
  42                         con = eccent * Math.sin(phi);
  43                         dphi = Math.PI/2 - 2 * Math.atan(ts * Math.pow((1.0 - con)/(1.0 + con), 0.5 * eccent)) - phi;
  44                         phi += dphi;
  45                 }
  46
  47                 return new L.LatLng(phi * d, lng, unbounded);
  48         }
  49 };