UTCTAIBulletinAFilesLoader.java
/* Copyright 2002-2024 CS GROUP
* Licensed to CS GROUP (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
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*/
package org.orekit.time;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.hipparchus.util.FastMath;
import org.orekit.annotation.DefaultDataContext;
import org.orekit.data.AbstractSelfFeedingLoader;
import org.orekit.data.DataContext;
import org.orekit.data.DataLoader;
import org.orekit.data.DataProvidersManager;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
/** Loader for UTC-TAI extracted from bulletin A files.
* <p>This class is a modified version of {@code BulletinAFileLoader}
* that only parses the TAI-UTC header line and checks the UT1-UTC column
* for discontinuities.
* </p>
* <p>
* Note that extracting UTC-TAI from bulletin A files is <em>NOT</em>
* recommended. There are known issues in some past bulletin A
* (for example bulletina-xix-001.txt from 2006-01-05 has a wrong year
* for last leap second and bulletina-xxi-053.txt from 2008-12-31 has an
* off by one value for TAI-UTC on MJD 54832). This is a known problem,
* and the Earth Orientation Department at USNO told us this TAI-UTC
* data was only provided as a convenience and this data should rather
* be sourced from other official files. As the bulletin A files are
* a record of past publications, they cannot modify archived bulletins,
* hence the errors above will remain forever. This UTC-TAI loader should
* therefore be used with great care.
* </p>
* <p>
* This class is immutable and hence thread-safe
* </p>
* @author Luc Maisonobe
* @since 7.1
*/
public class UTCTAIBulletinAFilesLoader extends AbstractSelfFeedingLoader
implements UTCTAIOffsetsLoader {
/**
* Build a loader for IERS bulletins A files. This constructor uses the {@link
* DataContext#getDefault() default data context}.
*
* @param supportedNames regular expression for supported files names
*/
@DefaultDataContext
public UTCTAIBulletinAFilesLoader(final String supportedNames) {
this(supportedNames, DataContext.getDefault().getDataProvidersManager());
}
/**
* Build a loader for IERS bulletins A files.
*
* @param supportedNames regular expression for supported files names
* @param manager provides access to the bulletin A files.
*/
public UTCTAIBulletinAFilesLoader(final String supportedNames,
final DataProvidersManager manager) {
super(supportedNames, manager);
}
/** {@inheritDoc} */
@Override
public List<OffsetModel> loadOffsets() {
final Parser parser = new Parser();
this.feed(parser);
final SortedMap<Integer, Integer> taiUtc = parser.getTaiUtc();
final SortedMap<Integer, Double> ut1Utc = parser.getUt1Utc();
// identify UT1-UTC discontinuities
final List<Integer> leapDays = new ArrayList<>();
Map.Entry<Integer, Double> previous = null;
for (final Map.Entry<Integer, Double> entry : ut1Utc.entrySet()) {
if (previous != null) {
final double delta = entry.getValue() - previous.getValue();
if (FastMath.abs(delta) > 0.5) {
// discontinuity found between previous and current entry, a leap second has occurred
leapDays.add(entry.getKey());
}
}
previous = entry;
}
final List<OffsetModel> offsets = new ArrayList<>();
if (!taiUtc.isEmpty()) {
// find the start offset, before the first UT1-UTC entry
final Map.Entry<Integer, Integer> firstTaiMUtc = taiUtc.entrySet().iterator().next();
int offset = firstTaiMUtc.getValue();
final int refMJD = firstTaiMUtc.getKey();
for (final int leapMJD : leapDays) {
if (leapMJD > refMJD) {
break;
}
--offset;
}
// set all known time steps
for (final int leapMJD : leapDays) {
offsets.add(new OffsetModel(new DateComponents(DateComponents.MODIFIED_JULIAN_EPOCH, leapMJD),
++offset));
}
// check for missing time steps
for (final Map.Entry<Integer, Integer> refTaiMUtc : taiUtc.entrySet()) {
final DateComponents refDC = new DateComponents(DateComponents.MODIFIED_JULIAN_EPOCH,
refTaiMUtc.getKey() + 1);
OffsetModel before = null;
for (final OffsetModel o : offsets) {
if (o.getStart().compareTo(refDC) < 0) {
before = o;
}
}
if (before != null) {
if (refTaiMUtc.getValue() != (int) FastMath.rint(before.getOffset())) {
throw new OrekitException(OrekitMessages.MISSING_EARTH_ORIENTATION_PARAMETERS_BETWEEN_DATES,
before.getStart(), refDC);
}
}
}
// make sure we stop the linear drift that was used before 1972
if (offsets.isEmpty()) {
offsets.add(0, new OffsetModel(new DateComponents(1972, 1, 1), taiUtc.get(taiUtc.firstKey())));
} else {
if (offsets.get(0).getStart().getYear() > 1972) {
offsets.add(0, new OffsetModel(new DateComponents(1972, 1, 1),
((int) FastMath.rint(offsets.get(0).getOffset())) - 1));
}
}
}
return offsets;
}
/** Internal class performing the parsing. */
private static class Parser implements DataLoader {
/** Regular expression matching blanks at start of line. */
private static final String LINE_START_REGEXP = "^\\p{Blank}+";
/** Regular expression matching blanks at end of line. */
private static final String LINE_END_REGEXP = "\\p{Blank}*$";
/** Regular expression matching integers. */
private static final String INTEGER_REGEXP = "[-+]?\\p{Digit}+";
/** Regular expression matching real numbers. */
private static final String REAL_REGEXP = "[-+]?(?:(?:\\p{Digit}+(?:\\.\\p{Digit}*)?)|(?:\\.\\p{Digit}+))(?:[eE][-+]?\\p{Digit}+)?";
/** Regular expression matching an integer field to store. */
private static final String STORED_INTEGER_FIELD = "\\p{Blank}*(" + INTEGER_REGEXP + ")";
/** regular expression matching a Modified Julian Day field to store. */
private static final String STORED_MJD_FIELD = "\\p{Blank}+(\\p{Digit}\\p{Digit}\\p{Digit}\\p{Digit}\\p{Digit})";
/** Regular expression matching a real field to store. */
private static final String STORED_REAL_FIELD = "\\p{Blank}+(" + REAL_REGEXP + ")";
/** Regular expression matching a real field to ignore. */
private static final String IGNORED_REAL_FIELD = "\\p{Blank}+" + REAL_REGEXP;
/** Enum for files sections, in expected order.
* <p>The bulletin A weekly data files contain several sections,
* each introduced with some fixed header text and followed by tabular data.
* </p>
*/
private enum Section {
/** Earth Orientation Parameters rapid service. */
// section 2 always contain rapid service data including error fields
// COMBINED EARTH ORIENTATION PARAMETERS:
//
// IERS Rapid Service
// MJD x error y error UT1-UTC error
// " " " " s s
// 13 8 30 56534 0.16762 .00009 0.32705 .00009 0.038697 0.000019
// 13 8 31 56535 0.16669 .00010 0.32564 .00010 0.038471 0.000019
// 13 9 1 56536 0.16592 .00009 0.32410 .00010 0.038206 0.000024
// 13 9 2 56537 0.16557 .00009 0.32270 .00009 0.037834 0.000024
// 13 9 3 56538 0.16532 .00009 0.32147 .00010 0.037351 0.000024
// 13 9 4 56539 0.16488 .00009 0.32044 .00010 0.036756 0.000023
// 13 9 5 56540 0.16435 .00009 0.31948 .00009 0.036036 0.000024
EOP_RAPID_SERVICE("^ *COMBINED EARTH ORIENTATION PARAMETERS: *$",
LINE_START_REGEXP +
STORED_INTEGER_FIELD + STORED_INTEGER_FIELD + STORED_INTEGER_FIELD +
STORED_MJD_FIELD +
IGNORED_REAL_FIELD + IGNORED_REAL_FIELD +
IGNORED_REAL_FIELD + IGNORED_REAL_FIELD +
STORED_REAL_FIELD + IGNORED_REAL_FIELD +
LINE_END_REGEXP),
/** Earth Orientation Parameters final values. */
// the first bulletin A of each month also includes final values for the
// period covering from day 2 of month m-2 to day 1 of month m-1.
// IERS Final Values
// MJD x y UT1-UTC
// " " s
// 13 7 2 56475 0.1441 0.3901 0.05717
// 13 7 3 56476 0.1457 0.3895 0.05716
// 13 7 4 56477 0.1467 0.3887 0.05728
// 13 7 5 56478 0.1477 0.3875 0.05755
// 13 7 6 56479 0.1490 0.3862 0.05793
// 13 7 7 56480 0.1504 0.3849 0.05832
// 13 7 8 56481 0.1516 0.3835 0.05858
// 13 7 9 56482 0.1530 0.3822 0.05877
EOP_FINAL_VALUES("^ *IERS Final Values *$",
LINE_START_REGEXP +
STORED_INTEGER_FIELD + STORED_INTEGER_FIELD + STORED_INTEGER_FIELD +
STORED_MJD_FIELD +
IGNORED_REAL_FIELD +
IGNORED_REAL_FIELD +
STORED_REAL_FIELD +
LINE_END_REGEXP),
/** TAI-UTC part of the Earth Orientation Parameters prediction.. */
// section 3 always contain prediction data without error fields
//
// PREDICTIONS:
// The following formulas will not reproduce the predictions given below,
// but may be used to extend the predictions beyond the end of this table.
//
// x = 0.0969 + 0.1110 cos A - 0.0103 sin A - 0.0435 cos C - 0.0171 sin C
// y = 0.3457 - 0.0061 cos A - 0.1001 sin A - 0.0171 cos C + 0.0435 sin C
// UT1-UTC = -0.0052 - 0.00104 (MJD - 56548) - (UT2-UT1)
//
// where A = 2*pi*(MJD-56540)/365.25 and C = 2*pi*(MJD-56540)/435.
//
// TAI-UTC(MJD 56541) = 35.0
// The accuracy may be estimated from the expressions:
// S x,y = 0.00068 (MJD-56540)**0.80 S t = 0.00025 (MJD-56540)**0.75
// Estimated accuracies are: Predictions 10 d 20 d 30 d 40 d
// Polar coord's 0.004 0.007 0.010 0.013
// UT1-UTC 0.0014 0.0024 0.0032 0.0040
//
// MJD x(arcsec) y(arcsec) UT1-UTC(sec)
// 2013 9 6 56541 0.1638 0.3185 0.03517
// 2013 9 7 56542 0.1633 0.3175 0.03420
// 2013 9 8 56543 0.1628 0.3164 0.03322
// 2013 9 9 56544 0.1623 0.3153 0.03229
// 2013 9 10 56545 0.1618 0.3142 0.03144
// 2013 9 11 56546 0.1612 0.3131 0.03071
// 2013 9 12 56547 0.1607 0.3119 0.03008
TAI_UTC("^ *PREDICTIONS: *$",
LINE_START_REGEXP +
"TAI-UTC\\(MJD *" +
STORED_MJD_FIELD +
"\\) *= *" +
STORED_INTEGER_FIELD + "(?:\\.0*)?" +
LINE_END_REGEXP),
/** Earth Orientation Parameters prediction. */
// section 3 always contain prediction data without error fields
//
// PREDICTIONS:
// The following formulas will not reproduce the predictions given below,
// but may be used to extend the predictions beyond the end of this table.
//
// x = 0.0969 + 0.1110 cos A - 0.0103 sin A - 0.0435 cos C - 0.0171 sin C
// y = 0.3457 - 0.0061 cos A - 0.1001 sin A - 0.0171 cos C + 0.0435 sin C
// UT1-UTC = -0.0052 - 0.00104 (MJD - 56548) - (UT2-UT1)
//
// where A = 2*pi*(MJD-56540)/365.25 and C = 2*pi*(MJD-56540)/435.
//
// TAI-UTC(MJD 56541) = 35.0
// The accuracy may be estimated from the expressions:
// S x,y = 0.00068 (MJD-56540)**0.80 S t = 0.00025 (MJD-56540)**0.75
// Estimated accuracies are: Predictions 10 d 20 d 30 d 40 d
// Polar coord's 0.004 0.007 0.010 0.013
// UT1-UTC 0.0014 0.0024 0.0032 0.0040
//
// MJD x(arcsec) y(arcsec) UT1-UTC(sec)
// 2013 9 6 56541 0.1638 0.3185 0.03517
// 2013 9 7 56542 0.1633 0.3175 0.03420
// 2013 9 8 56543 0.1628 0.3164 0.03322
// 2013 9 9 56544 0.1623 0.3153 0.03229
// 2013 9 10 56545 0.1618 0.3142 0.03144
// 2013 9 11 56546 0.1612 0.3131 0.03071
// 2013 9 12 56547 0.1607 0.3119 0.03008
EOP_PREDICTION("^ *MJD *x\\(arcsec\\) *y\\(arcsec\\) *UT1-UTC\\(sec\\) *$",
LINE_START_REGEXP +
STORED_INTEGER_FIELD + STORED_INTEGER_FIELD + STORED_INTEGER_FIELD +
STORED_MJD_FIELD +
IGNORED_REAL_FIELD +
IGNORED_REAL_FIELD +
STORED_REAL_FIELD +
LINE_END_REGEXP);
/** Header pattern. */
private final Pattern header;
/** Data pattern. */
private final Pattern data;
/** Simple constructor.
* @param headerRegExp regular expression for header
* @param dataRegExp regular expression for data
*/
Section(final String headerRegExp, final String dataRegExp) {
this.header = Pattern.compile(headerRegExp);
this.data = Pattern.compile(dataRegExp);
}
/** Check if a line matches the section header.
* @param l line to check
* @return true if the line matches the header
*/
public boolean matchesHeader(final String l) {
return header.matcher(l).matches();
}
/** Get the data fields from a line.
* @param l line to parse
* @return extracted fields, or null if line does not match data format
*/
public String[] getFields(final String l) {
final Matcher matcher = data.matcher(l);
if (matcher.matches()) {
final String[] fields = new String[matcher.groupCount()];
for (int i = 0; i < fields.length; ++i) {
fields[i] = matcher.group(i + 1);
}
return fields;
} else {
return null;
}
}
}
/** TAI-UTC history. */
private final SortedMap<Integer, Integer> taiUtc;
/** UT1-UTC history. */
private final SortedMap<Integer, Double> ut1Utc;
/** Current line number. */
private int lineNumber;
/** Current line. */
private String line;
/** Simple constructor.
*/
Parser() {
this.taiUtc = new TreeMap<>();
this.ut1Utc = new TreeMap<>();
this.lineNumber = 0;
}
/** Get TAI-UTC history.
* @return TAI-UTC history
*/
public SortedMap<Integer, Integer> getTaiUtc() {
return taiUtc;
}
/** Get UT1-UTC history.
* @return UT1-UTC history
*/
public SortedMap<Integer, Double> getUt1Utc() {
return ut1Utc;
}
/** {@inheritDoc} */
@Override
public boolean stillAcceptsData() {
return true;
}
/** {@inheritDoc} */
@Override
public void loadData(final InputStream input, final String name)
throws IOException {
final List<Section> remaining = new ArrayList<>(Arrays.asList(Section.values()));
// set up a reader for line-oriented bulletin A files
try (BufferedReader reader = new BufferedReader(new InputStreamReader(input, StandardCharsets.UTF_8))) {
// loop over sections
for (Section section = nextSection(remaining, reader);
section != null;
section = nextSection(remaining, reader)) {
if (section == Section.TAI_UTC) {
loadTaiUtc(section, reader, name);
} else {
// load the values
loadTimeSteps(section, reader, name);
}
// remove the already parsed section from the list
remaining.remove(section);
}
}
lineNumber = 0;
// check that the mandatory sections have been parsed
if (remaining.contains(Section.EOP_RAPID_SERVICE) || remaining.contains(Section.EOP_PREDICTION)) {
throw new OrekitException(OrekitMessages.NOT_A_SUPPORTED_IERS_DATA_FILE, name);
}
}
/** Skip to next section header.
* @param sections sections to check for
* @param reader reader from where file content is obtained
* @return the next section or null if no section is found until end of file
* @exception IOException if data can't be read
*/
private Section nextSection(final List<Section> sections, final BufferedReader reader)
throws IOException {
for (line = reader.readLine(); line != null; line = reader.readLine()) {
++lineNumber;
for (Section section : sections) {
if (section.matchesHeader(line)) {
return section;
}
}
}
// we have reached end of file and not found a matching section header
return null;
}
/** Read TAI-UTC.
* @param section section to parse
* @param reader reader from where file content is obtained
* @param name name of the file (or zip entry)
* @exception IOException if data can't be read
*/
private void loadTaiUtc(final Section section, final BufferedReader reader, final String name)
throws IOException {
for (line = reader.readLine(); line != null; line = reader.readLine()) {
lineNumber++;
final String[] fields = section.getFields(line);
if (fields != null) {
// we have found the single line we are looking for
final int mjd = Integer.parseInt(fields[0]);
final int offset = Integer.parseInt(fields[1]);
taiUtc.put(mjd, offset);
return;
}
}
throw new OrekitException(OrekitMessages.UNEXPECTED_END_OF_FILE_AFTER_LINE,
name, lineNumber);
}
/** Read UT1-UTC.
* @param section section to parse
* @param reader reader from where file content is obtained
* @param name name of the file (or zip entry)
* @exception IOException if data can't be read
*/
private void loadTimeSteps(final Section section, final BufferedReader reader, final String name)
throws IOException {
boolean inValuesPart = false;
for (line = reader.readLine(); line != null; line = reader.readLine()) {
lineNumber++;
final String[] fields = section.getFields(line);
if (fields != null) {
// we are within the values part
inValuesPart = true;
// this is a data line, build an entry from the extracted fields
final int year = Integer.parseInt(fields[0]);
final int month = Integer.parseInt(fields[1]);
final int day = Integer.parseInt(fields[2]);
final int mjd = Integer.parseInt(fields[3]);
final DateComponents dc = new DateComponents(DateComponents.MODIFIED_JULIAN_EPOCH, mjd);
if ((dc.getYear() % 100) != (year % 100) ||
dc.getMonth() != month ||
dc.getDay() != day) {
throw new OrekitException(OrekitMessages.INCONSISTENT_DATES_IN_IERS_FILE,
name, year, month, day, mjd);
}
final double offset = Double.parseDouble(fields[4]);
ut1Utc.put(mjd, offset);
} else if (inValuesPart) {
// we leave values part
return;
}
}
throw new OrekitException(OrekitMessages.UNEXPECTED_END_OF_FILE_AFTER_LINE,
name, lineNumber);
}
}
}