49 lines
1.0 KiB
JavaScript
49 lines
1.0 KiB
JavaScript
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import {SIXTH, RA4, RA6, EPSLN} from './constants/values';
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import {default as Ellipsoid, WGS84} from './constants/Ellipsoid';
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import match from './match';
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export function eccentricity(a, b, rf, R_A) {
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var a2 = a * a; // used in geocentric
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var b2 = b * b; // used in geocentric
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var es = (a2 - b2) / a2; // e ^ 2
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var e = 0;
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if (R_A) {
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a *= 1 - es * (SIXTH + es * (RA4 + es * RA6));
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a2 = a * a;
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es = 0;
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} else {
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e = Math.sqrt(es); // eccentricity
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}
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var ep2 = (a2 - b2) / b2; // used in geocentric
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return {
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es: es,
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e: e,
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ep2: ep2
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};
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}
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export function sphere(a, b, rf, ellps, sphere) {
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if (!a) { // do we have an ellipsoid?
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var ellipse = match(Ellipsoid, ellps);
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if (!ellipse) {
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ellipse = WGS84;
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}
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a = ellipse.a;
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b = ellipse.b;
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rf = ellipse.rf;
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}
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if (rf && !b) {
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b = (1.0 - 1.0 / rf) * a;
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}
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if (rf === 0 || Math.abs(a - b) < EPSLN) {
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sphere = true;
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b = a;
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}
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return {
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a: a,
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b: b,
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rf: rf,
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sphere: sphere
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};
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}
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