Sha256: 0f4b6731df78a6db1687d116c636c7bf3363178f1a407ee6831f5a1aebe98588
Contents?: true
Size: 704 Bytes
Versions: 4
Compression:
Stored size: 704 Bytes
Contents
function eckert4(λ, φ) {
var k = (2 + π / 2) * Math.sin(φ);
φ /= 2;
for (var i = 0, δ = Infinity; i < 10 && Math.abs(δ) > ε; i++) {
var cosφ = Math.cos(φ);
φ -= δ = (φ + Math.sin(φ) * (cosφ + 2) - k) / (2 * cosφ * (1 + cosφ));
}
return [
2 / Math.sqrt(π * (4 + π)) * λ * (1 + Math.cos(φ)),
2 * Math.sqrt(π / (4 + π)) * Math.sin(φ)
];
}
eckert4.invert = function(x, y) {
var j = 2 * Math.sqrt(π / (4 + π)),
k = asin(y / cy),
c = Math.cos(k);
return [
x / (2 / Math.sqrt(π * (4 + π)) * (1 + c)),
asin((k + y / j * (c + 2)) / (2 + π / 2))
];
};
(d3.geo.eckert4 = function() { return projection(eckert4); }).raw = eckert4;
Version data entries
4 entries across 4 versions & 1 rubygems