SHMFormatReader.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
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*
* 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,
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package org.orekit.forces.gravity.potential;
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.Locale;
import java.util.regex.Pattern;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.Precision;
import org.orekit.annotation.DefaultDataContext;
import org.orekit.data.DataContext;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.DateComponents;
import org.orekit.time.TimeScale;
import org.orekit.utils.Constants;
/** Reader for the SHM gravity field format.
*
* <p> This format was used to describe the gravity field of EIGEN models
* published by the GFZ Potsdam up to 2003. It was then replaced by
* {@link ICGEMFormatReader ICGEM format}. The SHM format is described in
* <a href="http://op.gfz-potsdam.de/champ/docs_CHAMP/CH-FORMAT-REFLINKS.html"> Potsdam university
* website</a>.
*
* <p> The proper way to use this class is to call the {@link GravityFieldFactory}
* which will determine which reader to use with the selected gravity field file.</p>
*
* @see GravityFields
* @author Fabien Maussion
*/
public class SHMFormatReader extends PotentialCoefficientsReader {
/** Pattern for delimiting regular expressions. */
private static final Pattern SEPARATOR = Pattern.compile("\\s+");
/** First field labels. */
private static final String GRCOEF = "GRCOEF";
/** Second field labels. */
private static final String GRCOF2 = "GRCOF2";
/** Drift coefficients labels. */
private static final String GRDOTA = "GRDOTA";
/** Flag for Earth data. */
private static final int EARTH = 0x1;
/** Flag for degree/order. */
private static final int LIMITS = 0x2;
/** Flag for coefficients. */
private static final int COEFFS = 0x4;
/** Reference date. */
private AbsoluteDate referenceDate;
/** Converter from triangular to flat form. */
private Flattener dotFlattener;
/** Secular drift of the cosine coefficients. */
private double[] cDot;
/** Secular drift of the sine coefficients. */
private double[] sDot;
/** Simple constructor.
*
* <p>This constructor uses the {@link DataContext#getDefault() default data context}.
*
* @param supportedNames regular expression for supported files names
* @param missingCoefficientsAllowed if true, allows missing coefficients in the input data
* @see #SHMFormatReader(String, boolean, TimeScale)
*/
@DefaultDataContext
public SHMFormatReader(final String supportedNames, final boolean missingCoefficientsAllowed) {
this(supportedNames, missingCoefficientsAllowed,
DataContext.getDefault().getTimeScales().getTT());
}
/** Simple constructor.
* @param supportedNames regular expression for supported files names
* @param missingCoefficientsAllowed if true, allows missing coefficients in the input data
* @param timeScale for parsing dates.
* @since 10.1
*/
public SHMFormatReader(final String supportedNames,
final boolean missingCoefficientsAllowed,
final TimeScale timeScale) {
super(supportedNames, missingCoefficientsAllowed, timeScale);
reset();
}
/** {@inheritDoc} */
public void loadData(final InputStream input, final String name)
throws IOException, ParseException, OrekitException {
// reset the indicator before loading any data
reset();
boolean normalized = false;
TideSystem tideSystem = TideSystem.UNKNOWN;
Flattener flattener = null;
int dotDegree = -1;
int dotOrder = -1;
int flags = 0;
double[] c0 = null;
double[] s0 = null;
double[] c1 = null;
double[] s1 = null;
String line = null;
int lineNumber = 1;
try (BufferedReader r = new BufferedReader(new InputStreamReader(input, StandardCharsets.UTF_8))) {
line = r.readLine();
if (line != null &&
"FIRST ".equals(line.substring(0, 6)) &&
"SHM ".equals(line.substring(49, 56))) {
for (line = r.readLine(); line != null; line = r.readLine()) {
lineNumber++;
if (line.length() >= 6) {
final String[] tab = SEPARATOR.split(line);
// read the earth values
if ("EARTH".equals(tab[0])) {
setMu(parseDouble(tab[1]));
setAe(parseDouble(tab[2]));
flags |= EARTH;
}
// initialize the arrays
if ("SHM".equals(tab[0])) {
final int degree = FastMath.min(getMaxParseDegree(), Integer.parseInt(tab[1]));
final int order = FastMath.min(getMaxParseOrder(), degree);
flattener = new Flattener(degree, order);
c0 = buildFlatArray(flattener, missingCoefficientsAllowed() ? 0.0 : Double.NaN);
s0 = buildFlatArray(flattener, missingCoefficientsAllowed() ? 0.0 : Double.NaN);
c1 = buildFlatArray(flattener, 0.0);
s1 = buildFlatArray(flattener, 0.0);
final String lowerCaseLine = line.toLowerCase(Locale.US);
normalized = lowerCaseLine.contains("fully normalized");
if (lowerCaseLine.contains("exclusive permanent tide")) {
tideSystem = TideSystem.TIDE_FREE;
} else {
tideSystem = TideSystem.UNKNOWN;
}
flags |= LIMITS;
}
// fill the arrays
if (GRCOEF.equals(line.substring(0, 6)) || GRCOF2.equals(tab[0]) || GRDOTA.equals(tab[0])) {
final int i = Integer.parseInt(tab[1]);
final int j = Integer.parseInt(tab[2]);
if (flattener.withinRange(i, j)) {
if (GRDOTA.equals(tab[0])) {
// store the secular drift coefficients
parseCoefficient(tab[3], flattener, c1, i, j, "Cdot", name);
parseCoefficient(tab[4], flattener, s1, i, j, "Sdot", name);
dotDegree = FastMath.max(dotDegree, i);
dotOrder = FastMath.max(dotOrder, j);
// check the reference date (format yyyymmdd)
final DateComponents localRef = new DateComponents(Integer.parseInt(tab[7].substring(0, 4)),
Integer.parseInt(tab[7].substring(4, 6)),
Integer.parseInt(tab[7].substring(6, 8)));
if (referenceDate == null) {
// first reference found, store it
referenceDate = toDate(localRef);
} else if (!referenceDate.equals(toDate(localRef))) {
final AbsoluteDate localDate = toDate(localRef);
throw new OrekitException(OrekitMessages.SEVERAL_REFERENCE_DATES_IN_GRAVITY_FIELD,
referenceDate, localDate, name,
localDate.durationFrom(referenceDate));
}
} else {
// store the constant coefficients
parseCoefficient(tab[3], flattener, c0, i, j, "C", name);
parseCoefficient(tab[4], flattener, s0, i, j, "S", name);
}
}
flags |= COEFFS;
}
}
}
}
} catch (NumberFormatException nfe) {
throw new OrekitException(OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
lineNumber, name, line);
}
if (flags != (EARTH | LIMITS | COEFFS)) {
String loaderName = getClass().getName();
loaderName = loaderName.substring(loaderName.lastIndexOf('.') + 1);
throw new OrekitException(OrekitMessages.UNEXPECTED_FILE_FORMAT_ERROR_FOR_LOADER,
name, loaderName);
}
if (missingCoefficientsAllowed()) {
// ensure at least the (0, 0) element is properly set
if (Precision.equals(c0[flattener.index(0, 0)], 0.0, 0)) {
c0[flattener.index(0, 0)] = 1.0;
}
}
// resize secular drift arrays
if (dotDegree >= 0) {
dotFlattener = new Flattener(dotDegree, dotOrder);
cDot = new double[dotFlattener.arraySize()];
sDot = new double[dotFlattener.arraySize()];
for (int n = 0; n <= dotDegree; ++n) {
for (int m = 0; m <= FastMath.min(n, dotOrder); ++m) {
cDot[dotFlattener.index(n, m)] = c1[flattener.index(n, m)];
sDot[dotFlattener.index(n, m)] = s1[flattener.index(n, m)];
}
}
}
setRawCoefficients(normalized, flattener, c0, s0, name);
setTideSystem(tideSystem);
setReadComplete(true);
}
/** Reset instance before read.
* @since 11.1
*/
private void reset() {
setReadComplete(false);
referenceDate = null;
dotFlattener = null;
cDot = null;
sDot = null;
}
/** Get a provider for read spherical harmonics coefficients.
* <p>
* SHM fields do include time-dependent parts which are taken into account
* in the returned provider.
* </p>
* @param wantNormalized if true, the provider will provide normalized coefficients,
* otherwise it will provide un-normalized coefficients
* @param degree maximal degree
* @param order maximal order
* @return a new provider
* @since 6.0
*/
public RawSphericalHarmonicsProvider getProvider(final boolean wantNormalized,
final int degree, final int order) {
// get the constant part
RawSphericalHarmonicsProvider provider = getBaseProvider(wantNormalized, degree, order);
if (dotFlattener != null) {
// add the secular trend layer
final double scale = 1.0 / Constants.JULIAN_YEAR;
final Flattener rescaledFlattener = new Flattener(FastMath.min(degree, dotFlattener.getDegree()),
FastMath.min(order, dotFlattener.getOrder()));
provider = new SecularTrendSphericalHarmonics(provider, referenceDate, rescaledFlattener,
rescale(scale, wantNormalized, rescaledFlattener, dotFlattener, cDot),
rescale(scale, wantNormalized, rescaledFlattener, dotFlattener, sDot));
}
return provider;
}
}