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import Check from "./Check.js";
import Frozen from "./Frozen.js";
import defined from "./defined.js";
import EarthOrientationParametersSample from "./EarthOrientationParametersSample.js";
import JulianDate from "./JulianDate.js";
import LeapSecond from "./LeapSecond.js";
import Resource from "./Resource.js";
import RuntimeError from "./RuntimeError.js";
import TimeConstants from "./TimeConstants.js";
import TimeStandard from "./TimeStandard.js";
/**
* Specifies Earth polar motion coordinates and the difference between UT1 and UTC.
* These Earth Orientation Parameters (EOP) are primarily used in the transformation from
* the International Celestial Reference Frame (ICRF) to the International Terrestrial
* Reference Frame (ITRF).
* This object is normally not instantiated directly, use {@link EarthOrientationParameters.fromUrl}.
*
* @alias EarthOrientationParameters
* @constructor
*
* @param {object} [options] Object with the following properties:
* @param {object} [options.data] The actual EOP data. If neither this
* parameter nor options.data is specified, all EOP values are assumed
* to be 0.0.
* @param {boolean} [options.addNewLeapSeconds=true] True if leap seconds that
* are specified in the EOP data but not in {@link JulianDate.leapSeconds}
* should be added to {@link JulianDate.leapSeconds}. False if
* new leap seconds should be handled correctly in the context
* of the EOP data but otherwise ignored.
*
* @private
*/
function EarthOrientationParameters(options) {
options = options ?? Frozen.EMPTY_OBJECT;
this._dates = undefined;
this._samples = undefined;
this._dateColumn = -1;
this._xPoleWanderRadiansColumn = -1;
this._yPoleWanderRadiansColumn = -1;
this._ut1MinusUtcSecondsColumn = -1;
this._xCelestialPoleOffsetRadiansColumn = -1;
this._yCelestialPoleOffsetRadiansColumn = -1;
this._taiMinusUtcSecondsColumn = -1;
this._columnCount = 0;
this._lastIndex = -1;
this._addNewLeapSeconds = options.addNewLeapSeconds ?? true;
if (defined(options.data)) {
// Use supplied EOP data.
onDataReady(this, options.data);
} else {
// Use all zeros for EOP data.
onDataReady(this, {
columnNames: [
"dateIso8601",
"modifiedJulianDateUtc",
"xPoleWanderRadians",
"yPoleWanderRadians",
"ut1MinusUtcSeconds",
"lengthOfDayCorrectionSeconds",
"xCelestialPoleOffsetRadians",
"yCelestialPoleOffsetRadians",
"taiMinusUtcSeconds",
],
samples: [],
});
}
}
/**
*
* @param {Resource|string} [url] The URL from which to obtain EOP data. If neither this
* parameter nor options.data is specified, all EOP values are assumed
* to be 0.0. If options.data is specified, this parameter is
* ignored.
* @param {object} [options] Object with the following properties:
* @param {boolean} [options.addNewLeapSeconds=true] True if leap seconds that
* are specified in the EOP data but not in {@link JulianDate.leapSeconds}
* should be added to {@link JulianDate.leapSeconds}. False if
* new leap seconds should be handled correctly in the context
* of the EOP data but otherwise ignored.
*
* @example
* // An example EOP data file, EOP.json:
* {
* "columnNames" : ["dateIso8601","modifiedJulianDateUtc","xPoleWanderRadians","yPoleWanderRadians","ut1MinusUtcSeconds","lengthOfDayCorrectionSeconds","xCelestialPoleOffsetRadians","yCelestialPoleOffsetRadians","taiMinusUtcSeconds"],
* "samples" : [
* "2011-07-01T00:00:00Z",55743.0,2.117957047295119e-7,2.111518721609984e-6,-0.2908948,-2.956e-4,3.393695767766752e-11,3.3452143996557983e-10,34.0,
* "2011-07-02T00:00:00Z",55744.0,2.193297093339541e-7,2.115460256837405e-6,-0.29065,-1.824e-4,-8.241832578862112e-11,5.623838700870617e-10,34.0,
* "2011-07-03T00:00:00Z",55745.0,2.262286080161428e-7,2.1191157519929706e-6,-0.2905572,1.9e-6,-3.490658503988659e-10,6.981317007977318e-10,34.0
* ]
* }
*
* @example
* // Loading the EOP data
* const eop = await Cesium.EarthOrientationParameters.fromUrl('Data/EOP.json');
* Cesium.Transforms.earthOrientationParameters = eop;
*/
EarthOrientationParameters.fromUrl = async function (url, options) {
//>>includeStart('debug', pragmas.debug);
Check.defined("url", url);
//>>includeEnd('debug');
options = options ?? Frozen.EMPTY_OBJECT;
const resource = Resource.createIfNeeded(url);
// Download EOP data.
let eopData;
try {
eopData = await resource.fetchJson();
} catch (e) {
throw new RuntimeError(
`An error occurred while retrieving the EOP data from the URL ${resource.url}.`,
);
}
return new EarthOrientationParameters({
addNewLeapSeconds: options.addNewLeapSeconds,
data: eopData,
});
};
/**
* A default {@link EarthOrientationParameters} instance that returns zero for all EOP values.
*/
EarthOrientationParameters.NONE = Object.freeze({
compute: function (date, result) {
Iif (!defined(result)) {
result = new EarthOrientationParametersSample(0.0, 0.0, 0.0, 0.0, 0.0);
} else {
result.xPoleWander = 0.0;
result.yPoleWander = 0.0;
result.xPoleOffset = 0.0;
result.yPoleOffset = 0.0;
result.ut1MinusUtc = 0.0;
}
return result;
},
});
/**
* Computes the Earth Orientation Parameters (EOP) for a given date by interpolating.
* If the EOP data has not yet been download, this method returns undefined.
*
* @param {JulianDate} date The date for each to evaluate the EOP.
* @param {EarthOrientationParametersSample} [result] The instance to which to copy the result.
* If this parameter is undefined, a new instance is created and returned.
* @returns {EarthOrientationParametersSample} The EOP evaluated at the given date, or
* undefined if the data necessary to evaluate EOP at the date has not yet been
* downloaded.
*
* @exception {RuntimeError} The loaded EOP data has an error and cannot be used.
*
* @see EarthOrientationParameters#fromUrl
*/
EarthOrientationParameters.prototype.compute = function (date, result) {
// We cannot compute until the samples are available.
Iif (!defined(this._samples)) {
return undefined;
}
if (!defined(result)) {
result = new EarthOrientationParametersSample(0.0, 0.0, 0.0, 0.0, 0.0);
}
if (this._samples.length === 0) {
result.xPoleWander = 0.0;
result.yPoleWander = 0.0;
result.xPoleOffset = 0.0;
result.yPoleOffset = 0.0;
result.ut1MinusUtc = 0.0;
return result;
}
const dates = this._dates;
const lastIndex = this._lastIndex;
let before = 0;
let after = 0;
if (defined(lastIndex)) {
const previousIndexDate = dates[lastIndex];
const nextIndexDate = dates[lastIndex + 1];
const isAfterPrevious = JulianDate.lessThanOrEquals(
previousIndexDate,
date,
);
const isAfterLastSample = !defined(nextIndexDate);
const isBeforeNext =
isAfterLastSample || JulianDate.greaterThanOrEquals(nextIndexDate, date);
if (isAfterPrevious && isBeforeNext) {
before = lastIndex;
if (!isAfterLastSample && nextIndexDate.equals(date)) {
++before;
}
after = before + 1;
interpolate(this, dates, this._samples, date, before, after, result);
return result;
}
}
let index = binarySearch(dates, date, JulianDate.compare, this._dateColumn);
if (index >= 0) {
// If the next entry is the same date, use the later entry. This way, if two entries
// describe the same moment, one before a leap second and the other after, then we will use
// the post-leap second data.
Iif (index < dates.length - 1 && dates[index + 1].equals(date)) {
++index;
}
before = index;
after = index;
} else {
after = ~index;
before = after - 1;
// Use the first entry if the date requested is before the beginning of the data.
if (before < 0) {
before = 0;
}
}
this._lastIndex = before;
interpolate(this, dates, this._samples, date, before, after, result);
return result;
};
function compareLeapSecondDates(leapSecond, dateToFind) {
return JulianDate.compare(leapSecond.julianDate, dateToFind);
}
function onDataReady(eop, eopData) {
if (!defined(eopData.columnNames)) {
throw new RuntimeError(
"Error in loaded EOP data: The columnNames property is required.",
);
}
Iif (!defined(eopData.samples)) {
throw new RuntimeError(
"Error in loaded EOP data: The samples property is required.",
);
}
const dateColumn = eopData.columnNames.indexOf("modifiedJulianDateUtc");
const xPoleWanderRadiansColumn =
eopData.columnNames.indexOf("xPoleWanderRadians");
const yPoleWanderRadiansColumn =
eopData.columnNames.indexOf("yPoleWanderRadians");
const ut1MinusUtcSecondsColumn =
eopData.columnNames.indexOf("ut1MinusUtcSeconds");
const xCelestialPoleOffsetRadiansColumn = eopData.columnNames.indexOf(
"xCelestialPoleOffsetRadians",
);
const yCelestialPoleOffsetRadiansColumn = eopData.columnNames.indexOf(
"yCelestialPoleOffsetRadians",
);
const taiMinusUtcSecondsColumn =
eopData.columnNames.indexOf("taiMinusUtcSeconds");
Iif (
dateColumn < 0 ||
xPoleWanderRadiansColumn < 0 ||
yPoleWanderRadiansColumn < 0 ||
ut1MinusUtcSecondsColumn < 0 ||
xCelestialPoleOffsetRadiansColumn < 0 ||
yCelestialPoleOffsetRadiansColumn < 0 ||
taiMinusUtcSecondsColumn < 0
) {
throw new RuntimeError(
"Error in loaded EOP data: The columnNames property must include modifiedJulianDateUtc, xPoleWanderRadians, yPoleWanderRadians, ut1MinusUtcSeconds, xCelestialPoleOffsetRadians, yCelestialPoleOffsetRadians, and taiMinusUtcSeconds columns",
);
}
const samples = (eop._samples = eopData.samples);
const dates = (eop._dates = []);
eop._dateColumn = dateColumn;
eop._xPoleWanderRadiansColumn = xPoleWanderRadiansColumn;
eop._yPoleWanderRadiansColumn = yPoleWanderRadiansColumn;
eop._ut1MinusUtcSecondsColumn = ut1MinusUtcSecondsColumn;
eop._xCelestialPoleOffsetRadiansColumn = xCelestialPoleOffsetRadiansColumn;
eop._yCelestialPoleOffsetRadiansColumn = yCelestialPoleOffsetRadiansColumn;
eop._taiMinusUtcSecondsColumn = taiMinusUtcSecondsColumn;
eop._columnCount = eopData.columnNames.length;
eop._lastIndex = undefined;
let lastTaiMinusUtc;
const addNewLeapSeconds = eop._addNewLeapSeconds;
// Convert the ISO8601 dates to JulianDates.
for (let i = 0, len = samples.length; i < len; i += eop._columnCount) {
const mjd = samples[i + dateColumn];
const taiMinusUtc = samples[i + taiMinusUtcSecondsColumn];
const day = mjd + TimeConstants.MODIFIED_JULIAN_DATE_DIFFERENCE;
const date = new JulianDate(day, taiMinusUtc, TimeStandard.TAI);
dates.push(date);
if (addNewLeapSeconds) {
if (taiMinusUtc !== lastTaiMinusUtc && defined(lastTaiMinusUtc)) {
// We crossed a leap second boundary, so add the leap second
// if it does not already exist.
const leapSeconds = JulianDate.leapSeconds;
const leapSecondIndex = binarySearch(
leapSeconds,
date,
compareLeapSecondDates,
);
if (leapSecondIndex < 0) {
const leapSecond = new LeapSecond(date, taiMinusUtc);
leapSeconds.splice(~leapSecondIndex, 0, leapSecond);
}
}
lastTaiMinusUtc = taiMinusUtc;
}
}
}
function fillResultFromIndex(eop, samples, index, columnCount, result) {
const start = index * columnCount;
result.xPoleWander = samples[start + eop._xPoleWanderRadiansColumn];
result.yPoleWander = samples[start + eop._yPoleWanderRadiansColumn];
result.xPoleOffset = samples[start + eop._xCelestialPoleOffsetRadiansColumn];
result.yPoleOffset = samples[start + eop._yCelestialPoleOffsetRadiansColumn];
result.ut1MinusUtc = samples[start + eop._ut1MinusUtcSecondsColumn];
}
function linearInterp(dx, y1, y2) {
return y1 + dx * (y2 - y1);
}
function interpolate(eop, dates, samples, date, before, after, result) {
const columnCount = eop._columnCount;
// First check the bounds on the EOP data
// If we are after the bounds of the data, return zeros.
// The 'before' index should never be less than zero.
if (after > dates.length - 1) {
result.xPoleWander = 0;
result.yPoleWander = 0;
result.xPoleOffset = 0;
result.yPoleOffset = 0;
result.ut1MinusUtc = 0;
return result;
}
const beforeDate = dates[before];
const afterDate = dates[after];
if (beforeDate.equals(afterDate) || date.equals(beforeDate)) {
fillResultFromIndex(eop, samples, before, columnCount, result);
return result;
} else Iif (date.equals(afterDate)) {
fillResultFromIndex(eop, samples, after, columnCount, result);
return result;
}
const factor =
JulianDate.secondsDifference(date, beforeDate) /
JulianDate.secondsDifference(afterDate, beforeDate);
const startBefore = before * columnCount;
const startAfter = after * columnCount;
// Handle UT1 leap second edge case
let beforeUt1MinusUtc = samples[startBefore + eop._ut1MinusUtcSecondsColumn];
let afterUt1MinusUtc = samples[startAfter + eop._ut1MinusUtcSecondsColumn];
const offsetDifference = afterUt1MinusUtc - beforeUt1MinusUtc;
if (offsetDifference > 0.5 || offsetDifference < -0.5) {
// The absolute difference between the values is more than 0.5, so we may have
// crossed a leap second. Check if this is the case and, if so, adjust the
// afterValue to account for the leap second. This way, our interpolation will
// produce reasonable results.
const beforeTaiMinusUtc =
samples[startBefore + eop._taiMinusUtcSecondsColumn];
const afterTaiMinusUtc =
samples[startAfter + eop._taiMinusUtcSecondsColumn];
Eif (beforeTaiMinusUtc !== afterTaiMinusUtc) {
Iif (afterDate.equals(date)) {
// If we are at the end of the leap second interval, take the second value
// Otherwise, the interpolation below will yield the wrong side of the
// discontinuity
// At the end of the leap second, we need to start accounting for the jump
beforeUt1MinusUtc = afterUt1MinusUtc;
} else {
// Otherwise, remove the leap second so that the interpolation is correct
afterUt1MinusUtc -= afterTaiMinusUtc - beforeTaiMinusUtc;
}
}
}
result.xPoleWander = linearInterp(
factor,
samples[startBefore + eop._xPoleWanderRadiansColumn],
samples[startAfter + eop._xPoleWanderRadiansColumn],
);
result.yPoleWander = linearInterp(
factor,
samples[startBefore + eop._yPoleWanderRadiansColumn],
samples[startAfter + eop._yPoleWanderRadiansColumn],
);
result.xPoleOffset = linearInterp(
factor,
samples[startBefore + eop._xCelestialPoleOffsetRadiansColumn],
samples[startAfter + eop._xCelestialPoleOffsetRadiansColumn],
);
result.yPoleOffset = linearInterp(
factor,
samples[startBefore + eop._yCelestialPoleOffsetRadiansColumn],
samples[startAfter + eop._yCelestialPoleOffsetRadiansColumn],
);
result.ut1MinusUtc = linearInterp(
factor,
beforeUt1MinusUtc,
afterUt1MinusUtc,
);
return result;
}
export default EarthOrientationParameters;
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