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import Frozen from "./Frozen.js";
import defined from "./defined.js";
import Iau2006XysSample from "./Iau2006XysSample.js";
import JulianDate from "./JulianDate.js";
import Resource from "./Resource.js";
import TimeStandard from "./TimeStandard.js";
/**
* A set of IAU2006 XYS data that is used to evaluate the transformation between the International
* Celestial Reference Frame (ICRF) and the International Terrestrial Reference Frame (ITRF).
*
* @alias Iau2006XysData
* @constructor
*
* @param {object} [options] Object with the following properties:
* @param {Resource|string} [options.xysFileUrlTemplate='Assets/IAU2006_XYS/IAU2006_XYS_{0}.json'] A template URL for obtaining the XYS data. In the template,
* `{0}` will be replaced with the file index.
* @param {number} [options.interpolationOrder=9] The order of interpolation to perform on the XYS data.
* @param {number} [options.sampleZeroJulianEphemerisDate=2442396.5] The Julian ephemeris date (JED) of the
* first XYS sample.
* @param {number} [options.stepSizeDays=1.0] The step size, in days, between successive XYS samples.
* @param {number} [options.samplesPerXysFile=1000] The number of samples in each XYS file.
* @param {number} [options.totalSamples=27426] The total number of samples in all XYS files.
*
* @private
*/
function Iau2006XysData(options) {
options = options ?? Frozen.EMPTY_OBJECT;
this._xysFileUrlTemplate = Resource.createIfNeeded(
options.xysFileUrlTemplate,
);
this._interpolationOrder = options.interpolationOrder ?? 9;
this._sampleZeroJulianEphemerisDate =
options.sampleZeroJulianEphemerisDate ?? 2442396.5;
this._sampleZeroDateTT = new JulianDate(
this._sampleZeroJulianEphemerisDate,
0.0,
TimeStandard.TAI,
);
this._stepSizeDays = options.stepSizeDays ?? 1.0;
this._samplesPerXysFile = options.samplesPerXysFile ?? 1000;
this._totalSamples = options.totalSamples ?? 27426;
this._samples = new Array(this._totalSamples * 3);
this._chunkDownloadsInProgress = [];
const order = this._interpolationOrder;
// Compute denominators and X values for interpolation.
const denom = (this._denominators = new Array(order + 1));
const xTable = (this._xTable = new Array(order + 1));
const stepN = Math.pow(this._stepSizeDays, order);
for (let i = 0; i <= order; ++i) {
denom[i] = stepN;
xTable[i] = i * this._stepSizeDays;
for (let j = 0; j <= order; ++j) {
if (j !== i) {
denom[i] *= i - j;
}
}
denom[i] = 1.0 / denom[i];
}
// Allocate scratch arrays for interpolation.
this._work = new Array(order + 1);
this._coef = new Array(order + 1);
}
const julianDateScratch = new JulianDate(0, 0.0, TimeStandard.TAI);
function getDaysSinceEpoch(xys, dayTT, secondTT) {
const dateTT = julianDateScratch;
dateTT.dayNumber = dayTT;
dateTT.secondsOfDay = secondTT;
return JulianDate.daysDifference(dateTT, xys._sampleZeroDateTT);
}
/**
* Preloads XYS data for a specified date range.
*
* @param {number} startDayTT The Julian day number of the beginning of the interval to preload, expressed in
* the Terrestrial Time (TT) time standard.
* @param {number} startSecondTT The seconds past noon of the beginning of the interval to preload, expressed in
* the Terrestrial Time (TT) time standard.
* @param {number} stopDayTT The Julian day number of the end of the interval to preload, expressed in
* the Terrestrial Time (TT) time standard.
* @param {number} stopSecondTT The seconds past noon of the end of the interval to preload, expressed in
* the Terrestrial Time (TT) time standard.
* @returns {Promise<void>} A promise that, when resolved, indicates that the requested interval has been
* preloaded.
*/
Iau2006XysData.prototype.preload = function (
startDayTT,
startSecondTT,
stopDayTT,
stopSecondTT,
) {
const startDaysSinceEpoch = getDaysSinceEpoch(
this,
startDayTT,
startSecondTT,
);
const stopDaysSinceEpoch = getDaysSinceEpoch(this, stopDayTT, stopSecondTT);
let startIndex =
(startDaysSinceEpoch / this._stepSizeDays - this._interpolationOrder / 2) |
0;
if (startIndex < 0) {
startIndex = 0;
}
let stopIndex =
(stopDaysSinceEpoch / this._stepSizeDays - this._interpolationOrder / 2) |
(0 + this._interpolationOrder);
Iif (stopIndex >= this._totalSamples) {
stopIndex = this._totalSamples - 1;
}
const startChunk = (startIndex / this._samplesPerXysFile) | 0;
const stopChunk = (stopIndex / this._samplesPerXysFile) | 0;
const promises = [];
for (let i = startChunk; i <= stopChunk; ++i) {
promises.push(requestXysChunk(this, i));
}
return Promise.all(promises);
};
/**
* Computes the XYS values for a given date by interpolating. If the required data is not yet downloaded,
* this method will return undefined.
*
* @param {number} dayTT The Julian day number for which to compute the XYS value, expressed in
* the Terrestrial Time (TT) time standard.
* @param {number} secondTT The seconds past noon of the date for which to compute the XYS value, expressed in
* the Terrestrial Time (TT) time standard.
* @param {Iau2006XysSample} [result] The instance to which to copy the interpolated result. If this parameter
* is undefined, a new instance is allocated and returned.
* @returns {Iau2006XysSample} The interpolated XYS values, or undefined if the required data for this
* computation has not yet been downloaded.
*
* @see Iau2006XysData#preload
*/
Iau2006XysData.prototype.computeXysRadians = function (
dayTT,
secondTT,
result,
) {
const daysSinceEpoch = getDaysSinceEpoch(this, dayTT, secondTT);
if (daysSinceEpoch < 0.0) {
// Can't evaluate prior to the epoch of the data.
return undefined;
}
const centerIndex = (daysSinceEpoch / this._stepSizeDays) | 0;
if (centerIndex >= this._totalSamples) {
// Can't evaluate after the last sample in the data.
return undefined;
}
const degree = this._interpolationOrder;
let firstIndex = centerIndex - ((degree / 2) | 0);
if (firstIndex < 0) {
firstIndex = 0;
}
let lastIndex = firstIndex + degree;
Iif (lastIndex >= this._totalSamples) {
lastIndex = this._totalSamples - 1;
firstIndex = lastIndex - degree;
if (firstIndex < 0) {
firstIndex = 0;
}
}
// Are all the samples we need present?
// We can assume so if the first and last are present
let isDataMissing = false;
const samples = this._samples;
if (!defined(samples[firstIndex * 3])) {
requestXysChunk(this, (firstIndex / this._samplesPerXysFile) | 0);
isDataMissing = true;
}
if (!defined(samples[lastIndex * 3])) {
requestXysChunk(this, (lastIndex / this._samplesPerXysFile) | 0);
isDataMissing = true;
}
if (isDataMissing) {
return undefined;
}
if (!defined(result)) {
result = new Iau2006XysSample(0.0, 0.0, 0.0);
} else {
result.x = 0.0;
result.y = 0.0;
result.s = 0.0;
}
const x = daysSinceEpoch - firstIndex * this._stepSizeDays;
const work = this._work;
const denom = this._denominators;
const coef = this._coef;
const xTable = this._xTable;
let i, j;
for (i = 0; i <= degree; ++i) {
work[i] = x - xTable[i];
}
for (i = 0; i <= degree; ++i) {
coef[i] = 1.0;
for (j = 0; j <= degree; ++j) {
if (j !== i) {
coef[i] *= work[j];
}
}
coef[i] *= denom[i];
let sampleIndex = (firstIndex + i) * 3;
result.x += coef[i] * samples[sampleIndex++];
result.y += coef[i] * samples[sampleIndex++];
result.s += coef[i] * samples[sampleIndex];
}
return result;
};
function requestXysChunk(xysData, chunkIndex) {
if (xysData._chunkDownloadsInProgress[chunkIndex]) {
// Chunk has already been requested.
return xysData._chunkDownloadsInProgress[chunkIndex];
}
let chunkUrl;
const xysFileUrlTemplate = xysData._xysFileUrlTemplate;
if (defined(xysFileUrlTemplate)) {
chunkUrl = xysFileUrlTemplate.getDerivedResource({
templateValues: {
0: chunkIndex,
},
});
} else {
chunkUrl = new Resource({
url: buildModuleUrl(`Assets/IAU2006_XYS/IAU2006_XYS_${chunkIndex}.json`),
});
}
const promise = chunkUrl.fetchJson().then(function (chunk) {
xysData._chunkDownloadsInProgress[chunkIndex] = false;
const samples = xysData._samples;
const newSamples = chunk.samples;
const startIndex = chunkIndex * xysData._samplesPerXysFile * 3;
for (let i = 0, len = newSamples.length; i < len; ++i) {
samples[startIndex + i] = newSamples[i];
}
});
xysData._chunkDownloadsInProgress[chunkIndex] = promise;
return promise;
}
export default Iau2006XysData;
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