First commit

node_modules/proj4/lib/projections/gnom.js

@@ -0,0 +1,104 @@
+import adjust_lon from '../common/adjust_lon';
+import asinz from '../common/asinz';
+import {EPSLN} from '../constants/values';
+
+/*
+  reference:
+    Wolfram Mathworld "Gnomonic Projection"
+    http://mathworld.wolfram.com/GnomonicProjection.html
+    Accessed: 12th November 2009
+  */
+export function init() {
+
+  /* Place parameters in static storage for common use
+      -------------------------------------------------*/
+  this.sin_p14 = Math.sin(this.lat0);
+  this.cos_p14 = Math.cos(this.lat0);
+  // Approximation for projecting points to the horizon (infinity)
+  this.infinity_dist = 1000 * this.a;
+  this.rc = 1;
+}
+
+/* Gnomonic forward equations--mapping lat,long to x,y
+    ---------------------------------------------------*/
+export function forward(p) {
+  var sinphi, cosphi; /* sin and cos value        */
+  var dlon; /* delta longitude value      */
+  var coslon; /* cos of longitude        */
+  var ksp; /* scale factor          */
+  var g;
+  var x, y;
+  var lon = p.x;
+  var lat = p.y;
+  /* Forward equations
+      -----------------*/
+  dlon = adjust_lon(lon - this.long0);
+
+  sinphi = Math.sin(lat);
+  cosphi = Math.cos(lat);
+
+  coslon = Math.cos(dlon);
+  g = this.sin_p14 * sinphi + this.cos_p14 * cosphi * coslon;
+  ksp = 1;
+  if ((g > 0) || (Math.abs(g) <= EPSLN)) {
+    x = this.x0 + this.a * ksp * cosphi * Math.sin(dlon) / g;
+    y = this.y0 + this.a * ksp * (this.cos_p14 * sinphi - this.sin_p14 * cosphi * coslon) / g;
+  }
+  else {
+
+    // Point is in the opposing hemisphere and is unprojectable
+    // We still need to return a reasonable point, so we project
+    // to infinity, on a bearing
+    // equivalent to the northern hemisphere equivalent
+    // This is a reasonable approximation for short shapes and lines that
+    // straddle the horizon.
+
+    x = this.x0 + this.infinity_dist * cosphi * Math.sin(dlon);
+    y = this.y0 + this.infinity_dist * (this.cos_p14 * sinphi - this.sin_p14 * cosphi * coslon);
+
+  }
+  p.x = x;
+  p.y = y;
+  return p;
+}
+
+export function inverse(p) {
+  var rh; /* Rho */
+  var sinc, cosc;
+  var c;
+  var lon, lat;
+
+  /* Inverse equations
+      -----------------*/
+  p.x = (p.x - this.x0) / this.a;
+  p.y = (p.y - this.y0) / this.a;
+
+  p.x /= this.k0;
+  p.y /= this.k0;
+
+  if ((rh = Math.sqrt(p.x * p.x + p.y * p.y))) {
+    c = Math.atan2(rh, this.rc);
+    sinc = Math.sin(c);
+    cosc = Math.cos(c);
+
+    lat = asinz(cosc * this.sin_p14 + (p.y * sinc * this.cos_p14) / rh);
+    lon = Math.atan2(p.x * sinc, rh * this.cos_p14 * cosc - p.y * this.sin_p14 * sinc);
+    lon = adjust_lon(this.long0 + lon);
+  }
+  else {
+    lat = this.phic0;
+    lon = 0;
+  }
+
+  p.x = lon;
+  p.y = lat;
+  return p;
+}
+
+export var names = ["gnom"];
+export default {
+  init: init,
+  forward: forward,
+  inverse: inverse,
+  names: names
+};