Sha256: ea501d5de4776dc1adcd3b583ad2ae9442bc8f1e27327051000dde896bc58428
Contents?: true
Size: 1.53 KB
Versions: 4
Compression:
Stored size: 1.53 KB
Contents
function hill(K) {
var L = 1 + K,
sinβ = Math.sin(1 / L),
β = asin(sinβ),
A = 2 * Math.sqrt(π / (B = π + 4 * β * L)),
B,
ρ0 = .5 * A * (L + Math.sqrt(K * (2 + K))),
K2 = K * K,
L2 = L * L;
function forward(λ, φ) {
var t = 1 - Math.sin(φ),
ρ,
ω;
if (t && t < 2) {
var θ = π / 2 - φ, i = 25, δ;
do {
var sinθ = Math.sin(θ),
cosθ = Math.cos(θ),
β_β1 = β + Math.atan2(sinθ, L - cosθ),
C = 1 + L2 - 2 * L * cosθ;
θ -= δ = (θ - K2 * β - L * sinθ + C * β_β1 - .5 * t * B) / (2 * L * sinθ * β_β1);
} while (Math.abs(δ) > ε2 && --i > 0);
ρ = A * Math.sqrt(C);
ω = λ * β_β1 / π;
} else {
ρ = A * (K + t);
ω = λ * β / π;
}
return [
ρ * Math.sin(ω),
ρ0 - ρ * Math.cos(ω)
];
};
forward.invert = function(x, y) {
var ρ2 = x * x + (y -= ρ0) * y,
cosθ = (1 + L2 - ρ2 / (A * A)) / (2 * L),
θ = acos(cosθ),
sinθ = Math.sin(θ),
β_β1 = β + Math.atan2(sinθ, L - cosθ);
return [
asin(x / Math.sqrt(ρ2)) * π / β_β1,
asin(1 - 2 * (θ - K2 * β - L * sinθ + (1 + L2 - 2 * L * cosθ) * β_β1) / B)
];
};
return forward;
}
function hillProjection() {
var K = 1,
m = projectionMutator(hill),
p = m(K);
p.ratio = function(_) {
if (!arguments.length) return K;
return m(K = +_);
};
return p;
}
(d3.geo.hill = hillProjection).raw = hill;
Version data entries
4 entries across 4 versions & 1 rubygems