52 lines
2.2 KiB
JavaScript
52 lines
2.2 KiB
JavaScript
/* *
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*
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* Equal Earth projection, an equal-area projection designed to minimize
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* distortion and remain pleasing to the eye.
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*
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* Invented by Bojan Šavrič, Bernhard Jenny, and Tom Patterson in 2018. It is
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* inspired by the widely used Robinson projection.
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*
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* */
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'use strict';
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var A1 = 1.340264, A2 = -0.081106, A3 = 0.000893, A4 = 0.003796, M = Math.sqrt(3) / 2.0, scale = 74.03120656864502;
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var EqualEarth = /** @class */ (function () {
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function EqualEarth() {
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this.bounds = {
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x1: -200.37508342789243,
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x2: 200.37508342789243,
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y1: -97.52595454902263,
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y2: 97.52595454902263
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};
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}
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EqualEarth.prototype.forward = function (lonLat) {
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var d = Math.PI / 180, paramLat = Math.asin(M * Math.sin(lonLat[1] * d)), paramLatSq = paramLat * paramLat, paramLatPow6 = paramLatSq * paramLatSq * paramLatSq;
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var x = lonLat[0] * d * Math.cos(paramLat) * scale / (M *
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(A1 +
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3 * A2 * paramLatSq +
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paramLatPow6 * (7 * A3 + 9 * A4 * paramLatSq)));
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var y = paramLat * scale * (A1 + A2 * paramLatSq + paramLatPow6 * (A3 + A4 * paramLatSq));
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return [x, y];
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};
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EqualEarth.prototype.inverse = function (xy) {
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var x = xy[0] / scale, y = xy[1] / scale, d = 180 / Math.PI, epsilon = 1e-9, iterations = 12;
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var paramLat = y, paramLatSq, paramLatPow6, fy, fpy, dlat, i;
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for (i = 0; i < iterations; ++i) {
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paramLatSq = paramLat * paramLat;
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paramLatPow6 = paramLatSq * paramLatSq * paramLatSq;
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fy = paramLat * (A1 + A2 * paramLatSq + paramLatPow6 * (A3 + A4 * paramLatSq)) - y;
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fpy = A1 + 3 * A2 * paramLatSq + paramLatPow6 * (7 * A3 + 9 * A4 * paramLatSq);
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paramLat -= dlat = fy / fpy;
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if (Math.abs(dlat) < epsilon) {
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break;
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}
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}
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paramLatSq = paramLat * paramLat;
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paramLatPow6 = paramLatSq * paramLatSq * paramLatSq;
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var lon = d * M * x * (A1 + 3 * A2 * paramLatSq + paramLatPow6 * (7 * A3 + 9 * A4 * paramLatSq)) / Math.cos(paramLat);
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var lat = d * Math.asin(Math.sin(paramLat) / M);
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return [lon, lat];
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};
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return EqualEarth;
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}());
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export default EqualEarth;
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