ootk-core
Version:
Orbital Object Toolkit. A modern typed replacement for satellite.js including SGP4 propagation, TLE parsing, Sun and Moon calculations, and more.
63 lines • 2.61 kB
JavaScript
/**
* @author Theodore Kruczek.
* @license MIT
* @copyright (c) 2022-2025 Theodore Kruczek Permission is
* hereby granted, free of charge, to any person obtaining a copy of this
* software and associated documentation files (the "Software"), to deal in the
* Software without restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do
* so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
import { factorial } from '../../utils/functions.js';
import { egm96 } from './egm96.js';
// / Container for EGM-96 data.
export class Egm96Data {
coeffs_;
// / Create a new [Egm96Data] object.
constructor(coeffs) {
this.coeffs_ = coeffs;
}
/**
* Create a new [Egm96Data] container given a list of EGM-96
* coefficient tuples [vals].
* @param vals List of EGM-96 coefficient tuples.
* @returns A new [Egm96Data] object.
*/
static fromVals(vals) {
const output = [];
for (const v of vals) {
const [l, m, clm, slm] = v;
const k = m === 0 ? 1 : 2;
const a = factorial(l + m);
const b = factorial(l - m) * (k * (2 * l + 1));
const nFac = Math.sqrt(a / b);
const normalizedClm = clm / nFac;
const normalizedSlm = slm / nFac;
output.push([l, m, normalizedClm, normalizedSlm]);
}
return new Egm96Data(output);
}
// / Return de-normalized EGM-96 coefficients for a given [l] and [m] index.
getCoeffs(l, m) {
return this.coeffs_[Egm96Data.index_(l, m)];
}
// / Return the EGM-96 index for a given [l] and [m] lookup.
static index_(l, m) {
return (((l - 2) * (l + 2) + l) >> 1) - 1 + m;
}
}
// / De-normalized EGM-96 data container.
export const egm96Data = Egm96Data.fromVals(egm96);
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