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var Holsen = {}; | |
(function(ns){ | |
ns.ellipsoids = { | |
"bessel": { | |
"a": 6377492.018, | |
"b": 6356173.509 | |
}, | |
"international": { | |
"a": 6378388.000, | |
"b": 6356911.946, | |
}, | |
"wgs84": { | |
"a": 6378137.000, | |
"b": 6356752.314 | |
} | |
}; | |
var toRad = function(deg) { | |
var r0 = 180 / Math.PI; | |
return deg / r0; | |
}; | |
var round = function(number, numDecimals) { | |
var pow = Math.pow(10, numDecimals); | |
return Math.round(number * pow) / pow; | |
} | |
var meridbue_constants = function(ellipsoid) { | |
var n = (ellipsoid.a - ellipsoid.b) / (ellipsoid.a + ellipsoid.b); | |
var k = ellipsoid.a / (n + 1); | |
var a1 = n; | |
var a2 = Math.pow(n, 2); | |
var a3 = Math.pow(n, 3); | |
var a4 = Math.pow(n, 4); | |
var k1 = 1 + (a2 / 4) + (a4 / 64); | |
var k2 = (a1 - a3 * (1 / 8)) * 3; | |
var k3 = (a2 - a4/4) * 15 / 8; | |
return { | |
"n": n, | |
"k": k, | |
"k1": k1, | |
"k2": k2, | |
"k3": k3 | |
}; | |
} | |
ns.meridbue = function(ellipsoid, b1, b2) { | |
return round(arc(toRad(b1), toRad(b2), meridbue_constants(ellipsoid)), 3); | |
}; | |
var arc = function(b1, b2, constants) { | |
var db = b2 - b1; | |
var bm = b2 - db / 2; | |
var g1 = constants.k * (constants.k1 * db - constants.k2 * Math.cos(2 * bm) * Math.sin(db) + constants.k3 * Math.cos(4 * bm) * Math.sin(2 * db)); | |
g1 = g1 - constants.k * (Math.pow(constants.n, 3) * Math.cos(6 * bm) * Math.sin(3 * db) * 35/24); | |
g1 = g1 + constants.k * (Math.pow(constants.n, 4) * Math.cos(8 * bm) * Math.sin(4 * db) * 315) / 256; | |
return g1; | |
}; | |
}(Holsen)); | |
console.log(Holsen.meridbue(Holsen.ellipsoids.bessel, 0, 58)) |
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