calculates a coordinate form a coordinate, a bearing and a distance

unvincenty.js

function unvincenty(lnglat, brng, dist) {
        var a = 6378137,
            b = 6356752.3142,
            f = 1 / 298.257223563,
            d2r = 0.017453292519943295,
            r2d = 57.29577951308232,
            s = dist,
            alpha1 = brng * d2r,
            sinAlpha1 = Math.sin(alpha1),
            cosAlpha1 = Math.cos(alpha1),
            tanU1 = (1 - f) * Math.tan(lnglat[1] * d2r),
            cosU1 = 1 / Math.sqrt((1 + tanU1 * tanU1)), sinU1 = tanU1 * cosU1,
            sigma1 = Math.atan2(tanU1, cosAlpha1),
            sinAlpha = cosU1 * sinAlpha1,
            cosSqAlpha = 1 - sinAlpha * sinAlpha,
            uSq = cosSqAlpha * (a * a - b * b) / (b * b),
            A = 1 + uSq / 16384 * (4096 + uSq * (-768 + uSq * (320 - 175 * uSq))),
            B = uSq / 1024 * (256 + uSq * (-128 + uSq * (74 - 47 * uSq))),
            sigma = s / (b * A),
            sigmaP = 2 * Math.PI;
        while (Math.abs(sigma - sigmaP) > 1e-12) {
            var cos2SigmaM = Math.cos(2 * sigma1 + sigma),
                sinSigma = Math.sin(sigma),
                cosSigma = Math.cos(sigma),
                deltaSigma = B * sinSigma * (cos2SigmaM + B / 4 * (cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM) - B / 6 * cos2SigmaM * (-3 + 4 * sinSigma * sinSigma) * (-3 + 4 * cos2SigmaM * cos2SigmaM)));
            sigmaP = sigma;
            sigma = s / (b * A) + deltaSigma;
        };
        var tmp = sinU1 * sinSigma - cosU1 * cosSigma * cosAlpha1,
            lat2 = Math.atan2(sinU1 * cosSigma + cosU1 * sinSigma * cosAlpha1, (1 - f) * Math.sqrt(sinAlpha * sinAlpha + tmp * tmp)),
            lambda = Math.atan2(sinSigma * sinAlpha1, cosU1 * cosSigma - sinU1 * sinSigma * cosAlpha1),
            C = f / 16 * cosSqAlpha * (4 + f * (4 - 3 * cosSqAlpha)),
            L = lambda - (1 - C) * f * sinAlpha * (sigma + C * sinSigma * (cos2SigmaM + C * cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM))),
            revAz = Math.atan2(sinAlpha, -tmp);

        return [lnglat[0] + L * r2d, lat2 * r2d];
    };