53 lines
1.3 KiB
JavaScript
53 lines
1.3 KiB
JavaScript
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import adjust_lon from '../common/adjust_lon';
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/*
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reference
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"New Equal-Area Map Projections for Noncircular Regions", John P. Snyder,
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The American Cartographer, Vol 15, No. 4, October 1988, pp. 341-355.
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*/
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/* Initialize the Miller Cylindrical projection
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-------------------------------------------*/
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export function init() {
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//no-op
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}
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/* Miller Cylindrical forward equations--mapping lat,long to x,y
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------------------------------------------------------------*/
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export function forward(p) {
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var lon = p.x;
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var lat = p.y;
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/* Forward equations
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-----------------*/
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var dlon = adjust_lon(lon - this.long0);
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var x = this.x0 + this.a * dlon;
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var y = this.y0 + this.a * Math.log(Math.tan((Math.PI / 4) + (lat / 2.5))) * 1.25;
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p.x = x;
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p.y = y;
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return p;
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}
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/* Miller Cylindrical inverse equations--mapping x,y to lat/long
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------------------------------------------------------------*/
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export function inverse(p) {
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p.x -= this.x0;
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p.y -= this.y0;
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var lon = adjust_lon(this.long0 + p.x / this.a);
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var lat = 2.5 * (Math.atan(Math.exp(0.8 * p.y / this.a)) - Math.PI / 4);
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p.x = lon;
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p.y = lat;
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return p;
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}
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export var names = ["Miller_Cylindrical", "mill"];
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export default {
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init: init,
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forward: forward,
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inverse: inverse,
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names: names
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};
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