Sha256: 8ddef48f16cc7353119756a7ba2fda393c9ade62dffc11a7bcb78199dfd9a7e9
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Contents
import "projection";
function aitoff(λ, φ) {
var cosφ = Math.cos(φ),
sinciα = sinci(acos(cosφ * Math.cos(λ /= 2)));
return [
2 * cosφ * Math.sin(λ) * sinciα,
Math.sin(φ) * sinciα
];
}
aitoff.invert = function(x, y) {
var λ = x, φ = y, i = 25;
do {
var sinλ = Math.sin(λ),
sinλ_2 = Math.sin(λ / 2),
cosλ_2 = Math.cos(λ / 2),
sinφ = Math.sin(φ),
cosφ = Math.cos(φ),
sin_2φ = Math.sin(2 * φ),
sin2φ = sinφ * sinφ,
cos2φ = cosφ * cosφ,
sin2λ_2 = sinλ_2 * sinλ_2,
C = 1 - cos2φ * cosλ_2 * cosλ_2,
E = C ? acos(cosφ * cosλ_2) * Math.sqrt(F = 1 / C) : F = 0,
F,
fx = 2 * E * cosφ * sinλ_2 - x,
fy = E * sinφ - y,
δxδλ = F * (cos2φ * sin2λ_2 + E * cosφ * cosλ_2 * sin2φ),
δxδφ = F * (.5 * sinλ * sin_2φ - E * 2 * sinφ * sinλ_2),
δyδλ = F * .25 * (sin_2φ * sinλ_2 - E * sinφ * cos2φ * sinλ),
δyδφ = F * (sin2φ * cosλ_2 + E * sin2λ_2 * cosφ),
denominator = δxδφ * δyδλ - δyδφ * δxδλ;
if (!denominator) break;
var δλ = (fy * δxδφ - fx * δyδφ) / denominator,
δφ = (fx * δyδλ - fy * δxδλ) / denominator;
λ -= δλ, φ -= δφ;
} while ((Math.abs(δλ) > ε || Math.abs(δφ) > ε) && --i > 0);
return [λ, φ];
};
(d3.geo.aitoff = function() { return projection(aitoff); }).raw = aitoff;
Version data entries
4 entries across 4 versions & 1 rubygems