Sha256: d421c515a5518c6ccf4765d4626cc981f92562cc34be941af9698e2f403d1730
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Size: 1.32 KB
Versions: 4
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Stored size: 1.32 KB
Contents
import "projection";
function larrivee(λ, φ) {
return [
λ * (1 + Math.sqrt(Math.cos(φ))) / 2,
φ / (Math.cos(φ / 2) * Math.cos(λ / 6))
];
}
larrivee.invert = function(x, y) {
var x0 = Math.abs(x),
y0 = Math.abs(y),
π_sqrt2 = π / Math.SQRT2,
λ = ε,
φ = π / 2;
if (y0 < π_sqrt2) φ *= y0 / π_sqrt2;
else λ += 6 * acos(π_sqrt2 / y0);
for (var i = 0; i < 25; i++) {
var sinφ = Math.sin(φ),
sqrtcosφ = asqrt(Math.cos(φ)),
sinφ_2 = Math.sin(φ / 2),
cosφ_2 = Math.cos(φ / 2),
sinλ_6 = Math.sin(λ / 6),
cosλ_6 = Math.cos(λ / 6),
f0 = .5 * λ * (1 + sqrtcosφ) - x0,
f1 = φ / (cosφ_2 * cosλ_6) - y0,
df0dφ = sqrtcosφ ? -.25 * λ * sinφ / sqrtcosφ : 0,
df0dλ = .5 * (1 + sqrtcosφ),
df1dφ = (1 + .5 * φ * sinφ_2 / cosφ_2) / (cosφ_2 * cosλ_6),
df1dλ = (φ / cosφ_2) * (sinλ_6 / 6) / (cosλ_6 * cosλ_6),
denom = df0dφ * df1dλ - df1dφ * df0dλ,
dφ = (f0 * df1dλ - f1 * df0dλ) / denom,
dλ = (f1 * df0dφ - f0 * df1dφ) / denom;
φ -= dφ;
λ -= dλ;
if (Math.abs(dφ) < ε && Math.abs(dλ) < ε) break;
}
return [x < 0 ? -λ : λ, y < 0 ? -φ : φ];
};
(d3.geo.larrivee = function() { return projection(larrivee); }).raw = larrivee;
Version data entries
4 entries across 4 versions & 1 rubygems