Sha256: 60e081c09603e510bc4b672adc0c17301df875210e036c3836679fe94dd66437
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Contents
import "math";
function ginzburgPolyconic(a, b, c, d, e, f, g, h) {
if (arguments.length < 8) h = 0;
function forward(λ, φ) {
if (!φ) return [a * λ / π, 0];
var φ2 = φ * φ,
xB = a + φ2 * (b + φ2 * (c + φ2 * d)),
yB = φ * (e - 1 + φ2 * (f - h + φ2 * g)),
m = (xB * xB + yB * yB) / (2 * yB),
α = λ * Math.asin(xB / m) / π;
return [m * Math.sin(α), φ * (1 + φ2 * h) + m * (1 - Math.cos(α))];
}
forward.invert = function(x, y) {
var λ = π * x / a,
φ = y,
δλ, δφ, i = 50;
do {
var φ2 = φ * φ,
xB = a + φ2 * (b + φ2 * (c + φ2 * d)),
yB = φ * (e - 1 + φ2 * (f - h + φ2 * g)),
p = xB * xB + yB * yB,
q = 2 * yB,
m = p / q,
m2 = m * m,
dαdλ = Math.asin(xB / m) / π,
α = λ * dαdλ;
xB2 = xB * xB,
dxBdφ = (2 * b + φ2 * (4 * c + φ2 * 6 * d)) * φ,
dyBdφ = e + φ2 * (3 * f + φ2 * 5 * g),
dpdφ = 2 * (xB * dxBdφ + yB * (dyBdφ - 1)),
dqdφ = 2 * (dyBdφ - 1),
dmdφ = (dpdφ * q - p * dqdφ) / (q * q),
cosα = Math.cos(α),
sinα = Math.sin(α),
mcosα = m * cosα,
msinα = m * sinα,
dαdφ = ((λ / π) * (1 / asqrt(1 - xB2 / m2)) * (dxBdφ * m - xB * dmdφ)) / m2,
fx = msinα - x,
fy = φ * (1 + φ2 * h) + m - mcosα - y,
δxδφ = dmdφ * sinα + mcosα * dαdφ,
δxδλ = mcosα * dαdλ,
δyδφ = 1 + dmdφ - (dmdφ * cosα - msinα * dαdφ),
δyδλ = msinα * dαdλ,
denominator = δxδφ * δyδλ - δyδφ * δxδλ;
if (!denominator) break;
λ -= δλ = (fy * δxδφ - fx * δyδφ) / denominator;
φ -= δφ = (fx * δyδλ - fy * δxδλ) / denominator;
} while ((Math.abs(δλ) > ε || Math.abs(δφ) > ε) && --i > 0);
return [λ, φ];
};
return forward;
}
Version data entries
2 entries across 2 versions & 1 rubygems