SEMParser.java
/* Copyright 2002-2021 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
* limitations under the License.
*/
package org.orekit.gnss;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.text.ParseException;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Pattern;
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;
import org.orekit.propagation.analytical.gnss.data.GNSSConstants;
import org.orekit.propagation.analytical.gnss.data.GPSAlmanac;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.GNSSDate;
import org.orekit.time.TimeScales;
/**
* This class reads SEM almanac files and provides {@link GPSAlmanac GPS almanacs}.
*
* <p>The definition of a SEM almanac comes from the
* <a href="http://www.navcen.uscg.gov/?pageName=gpsSem">U.S. COAST GUARD NAVIGATION CENTER</a>.</p>
*
* <p>The format of the files holding SEM almanacs is not precisely specified,
* so the parsing rules have been deduced from the downloadable files at
* <a href="http://www.navcen.uscg.gov/?pageName=gpsAlmanacs">NAVCEN</a>
* and at <a href="https://celestrak.com/GPS/almanac/SEM/">CelesTrak</a>.</p>
*
* @author Pascal Parraud
* @since 8.0
*
*/
public class SEMParser extends AbstractSelfFeedingLoader implements DataLoader {
// Constants
/** The source of the almanacs. */
private static final String SOURCE = "SEM";
/** the reference value for the inclination of GPS orbit: 0.30 semicircles. */
private static final double INC_REF = 0.30;
/** Default supported files name pattern. */
private static final String DEFAULT_SUPPORTED_NAMES = ".*\\.al3$";
/** Separator for parsing. */
private static final Pattern SEPARATOR = Pattern.compile("\\s+");
// Fields
/** the list of all the almanacs read from the file. */
private final List<GPSAlmanac> almanacs;
/** the list of all the PRN numbers of all the almanacs read from the file. */
private final List<Integer> prnList;
/** Set of time scales to use. */
private final TimeScales timeScales;
/** Simple constructor.
*
* <p>This constructor does not load any data by itself. Data must be loaded
* later on by calling one of the {@link #loadData() loadData()} method or
* the {@link #loadData(InputStream, String) loadData(inputStream, fileName)}
* method.</p>
*
* <p>The supported files names are used when getting data from the
* {@link #loadData() loadData()} method that relies on the
* {@link DataContext#getDefault() default data context}. They are useless when
* getting data from the {@link #loadData(InputStream, String) loadData(input, name)}
* method.</p>
*
* @param supportedNames regular expression for supported files names
* (if null, a default pattern matching files with a ".al3" extension will be used)
* @see #loadData()
* @see #SEMParser(String, DataProvidersManager, TimeScales)
*/
@DefaultDataContext
public SEMParser(final String supportedNames) {
this(supportedNames,
DataContext.getDefault().getDataProvidersManager(),
DataContext.getDefault().getTimeScales());
}
/**
* Create a SEM loader/parser with the given source of SEM auxiliary data files.
*
* <p>This constructor does not load any data by itself. Data must be loaded
* later on by calling one of the {@link #loadData() loadData()} method or
* the {@link #loadData(InputStream, String) loadData(inputStream, fileName)}
* method.</p>
*
* <p>The supported files names are used when getting data from the
* {@link #loadData() loadData()} method that relies on the
* {@code dataProvidersManager}. They are useless when
* getting data from the {@link #loadData(InputStream, String) loadData(input, name)}
* method.</p>
*
* @param supportedNames regular expression for supported files names
* (if null, a default pattern matching files with a ".al3" extension will be used)
* @param dataProvidersManager provides access to auxiliary data.
* @param timeScales to use when parsing the GPS dates.
* @see #loadData()
* @since 10.1
*/
public SEMParser(final String supportedNames,
final DataProvidersManager dataProvidersManager,
final TimeScales timeScales) {
super((supportedNames == null) ? DEFAULT_SUPPORTED_NAMES : supportedNames,
dataProvidersManager);
this.almanacs = new ArrayList<>();
this.prnList = new ArrayList<>();
this.timeScales = timeScales;
}
/**
* Loads almanacs.
*
* <p>The almanacs already loaded in the instance will be discarded
* and replaced by the newly loaded data.</p>
* <p>This feature is useful when the file selection is already set up by
* the {@link DataProvidersManager data providers manager} configuration.</p>
*
*/
public void loadData() {
// load the data from the configured data providers
feed(this);
if (almanacs.isEmpty()) {
throw new OrekitException(OrekitMessages.NO_SEM_ALMANAC_AVAILABLE);
}
}
@Override
public void loadData(final InputStream input, final String name)
throws IOException, ParseException, OrekitException {
// Clears the lists
almanacs.clear();
prnList.clear();
// Creates the reader
try (BufferedReader reader = new BufferedReader(new InputStreamReader(input, StandardCharsets.UTF_8))) {
// Reads the number of almanacs in the file from the first line
String[] token = getTokens(reader);
final int almanacNb = Integer.parseInt(token[0].trim());
// Reads the week number and the time of applicability from the second line
token = getTokens(reader);
final int week = Integer.parseInt(token[0].trim());
final double toa = Double.parseDouble(token[1].trim());
// Loop over data blocks
for (int i = 0; i < almanacNb; i++) {
// Reads the next lines to get one almanac from
readAlmanac(reader, week, toa);
}
} catch (IndexOutOfBoundsException | IOException e) {
throw new OrekitException(e, OrekitMessages.NOT_A_SUPPORTED_SEM_ALMANAC_FILE, name);
}
}
@Override
public boolean stillAcceptsData() {
return almanacs.isEmpty();
}
/**
* Gets all the {@link GPSAlmanac GPS almanacs} read from the file.
*
* @return the list of {@link GPSAlmanac} from the file
*/
public List<GPSAlmanac> getAlmanacs() {
return almanacs;
}
/**
* Gets the PRN numbers of all the {@link GPSAlmanac GPS almanacs} read from the file.
*
* @return the PRN numbers of all the {@link GPSAlmanac GPS almanacs} read from the file
*/
public List<Integer> getPRNNumbers() {
return prnList;
}
@Override
public String getSupportedNames() {
return super.getSupportedNames();
}
/**
* Builds {@link GPSAlmanac GPS almanacs} from data read in the file.
*
* @param reader the reader
* @param week the GPS week
* @param toa the Time of Applicability
* @throws IOException if GPSAlmanacs can't be built from the file
*/
private void readAlmanac(final BufferedReader reader, final int week, final double toa)
throws IOException {
// Skips the empty line
reader.readLine();
// Create an empty GPS almanac and set the source
final GPSAlmanac almanac = new GPSAlmanac();
almanac.setSource(SOURCE);
try {
// Reads the PRN number from the first line
String[] token = getTokens(reader);
almanac.setPRN(Integer.parseInt(token[0].trim()));
// Reads the SV number from the second line
token = getTokens(reader);
almanac.setSVN(Integer.parseInt(token[0].trim()));
// Reads the average URA number from the third line
token = getTokens(reader);
almanac.setURA(Integer.parseInt(token[0].trim()));
// Reads the fourth line to get ecc, inc and dom
token = getTokens(reader);
almanac.setE(Double.parseDouble(token[0].trim()));
almanac.setI0(getInclination(Double.parseDouble(token[1].trim())));
almanac.setOmegaDot(toRadians(Double.parseDouble(token[2].trim())));
// Reads the fifth line to get sqa, raan and aop
token = getTokens(reader);
almanac.setSqrtA(Double.parseDouble(token[0].trim()));
almanac.setOmega0(toRadians(Double.parseDouble(token[1].trim())));
almanac.setPa(toRadians(Double.parseDouble(token[2].trim())));
// Reads the sixth line to get anom, af0 and af1
token = getTokens(reader);
almanac.setM0(toRadians(Double.parseDouble(token[0].trim())));
almanac.setAf0(Double.parseDouble(token[1].trim()));
almanac.setAf1(Double.parseDouble(token[2].trim()));
// Reads the seventh line to get health
token = getTokens(reader);
almanac.setHealth(Integer.parseInt(token[0].trim()));
// Reads the eighth line to get Satellite Configuration
token = getTokens(reader);
almanac.setSatConfiguration(Integer.parseInt(token[0].trim()));
// Adds the almanac to the list
final AbsoluteDate date =
new GNSSDate(week, toa * 1000, SatelliteSystem.GPS, timeScales)
.getDate();
almanac.setDate(date);
almanac.setTime(toa);
almanac.setWeek(week);
almanacs.add(almanac);
// Adds the PRN to the list
prnList.add(almanac.getPRN());
} catch (IndexOutOfBoundsException aioobe) {
throw new IOException(aioobe);
}
}
/** Read a line and get tokens from.
* @param reader the reader
* @return the tokens from the read line
* @throws IOException if the line is null
*/
private String[] getTokens(final BufferedReader reader) throws IOException {
final String line = reader.readLine();
if (line != null) {
return SEPARATOR.split(line.trim());
} else {
throw new IOException();
}
}
/**
* Gets the inclination from the inclination offset.
*
* @param incOffset the inclination offset (semicircles)
* @return the inclination (rad)
*/
private double getInclination(final double incOffset) {
return toRadians(INC_REF + incOffset);
}
/**
* Converts an angular value from semicircles to radians.
*
* @param semicircles the angular value in semicircles
* @return the angular value in radians
*/
private double toRadians(final double semicircles) {
return GNSSConstants.GNSS_PI * semicircles;
}
}