EGMFormatReader.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
* limitations under the License.
*/
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.Arrays;
import java.util.Locale;
import java.util.regex.Pattern;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.Precision;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
import org.orekit.utils.Constants;
/**This reader is adapted to the EGM Format.
*
* <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 EGMFormatReader extends PotentialCoefficientsReader {
/** Pattern for delimiting regular expressions. */
private static final Pattern SEPARATOR = Pattern.compile("\\s+");
/** Start degree and order for coefficients container. */
private static final int START_DEGREE_ORDER = 120;
/** Flag for using WGS84 values for equatorial radius and central attraction coefficient. */
private final boolean useWgs84Coefficients;
/** Simple constructor.
* @param supportedNames regular expression for supported files names
* @param missingCoefficientsAllowed if true, allows missing coefficients in the input data
*/
public EGMFormatReader(final String supportedNames, final boolean missingCoefficientsAllowed) {
this(supportedNames, missingCoefficientsAllowed, false);
}
/**
* Simple constructor that allows overriding 'standard' EGM96 ae and mu with
* WGS84 variants.
*
* @param supportedNames regular expression for supported files names
* @param missingCoefficientsAllowed if true, allows missing coefficients in the input data
* @param useWgs84Coefficients if true, the WGS84 values will be used for equatorial radius
* and central attraction coefficient
*/
public EGMFormatReader(final String supportedNames, final boolean missingCoefficientsAllowed,
final boolean useWgs84Coefficients) {
super(supportedNames, missingCoefficientsAllowed, null);
this.useWgs84Coefficients = useWgs84Coefficients;
}
/** {@inheritDoc} */
public void loadData(final InputStream input, final String name)
throws IOException, ParseException, OrekitException {
// reset the indicator before loading any data
setReadComplete(false);
// both EGM96 and EGM2008 use the same values for ae and mu
// if a new EGM model changes them, we should have some selection logic
// based on file name (a better way would be to have the data in the
// file...)
if (this.useWgs84Coefficients) {
setAe(Constants.WGS84_EARTH_EQUATORIAL_RADIUS);
setMu(Constants.WGS84_EARTH_MU);
} else {
setAe(Constants.EGM96_EARTH_EQUATORIAL_RADIUS);
setMu(Constants.EGM96_EARTH_MU);
}
final String lowerCaseName = name.toLowerCase(Locale.US);
if (lowerCaseName.contains("2008") || lowerCaseName.contains("zerotide")) {
setTideSystem(TideSystem.ZERO_TIDE);
} else {
setTideSystem(TideSystem.TIDE_FREE);
}
Container container = new Container(START_DEGREE_ORDER, START_DEGREE_ORDER,
missingCoefficientsAllowed() ? 0.0 : Double.NaN);
boolean okFields = true;
int maxDegree = -1;
int maxOrder = -1;
int lineNumber = 0;
String line = null;
try (BufferedReader r = new BufferedReader(new InputStreamReader(input, StandardCharsets.UTF_8))) {
for (line = r.readLine(); okFields && line != null; line = r.readLine()) {
lineNumber++;
if (line.length() >= 15) {
// get the fields defining the current potential terms
final String[] tab = SEPARATOR.split(line.trim());
if (tab.length != 6) {
okFields = false;
}
final int i = Integer.parseInt(tab[0]);
final int j = Integer.parseInt(tab[1]);
if (i < 0 || j < 0) {
throw new OrekitException(OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
lineNumber, name, line);
}
if (i <= getMaxParseDegree() && j <= getMaxParseOrder()) {
while (!container.flattener.withinRange(i, j)) {
// we need to resize the container
container = container.resize(container.flattener.getDegree() * 2,
container.flattener.getOrder() * 2);
}
parseCoefficient(tab[2], container.flattener, container.c, i, j, "C", name);
parseCoefficient(tab[3], container.flattener, container.s, i, j, "S", name);
maxDegree = FastMath.max(maxDegree, i);
maxOrder = FastMath.max(maxOrder, j);
}
}
}
} catch (NumberFormatException nfe) {
throw new OrekitException(OrekitMessages.UNABLE_TO_PARSE_LINE_IN_FILE,
lineNumber, name, line);
}
if (missingCoefficientsAllowed() && getMaxParseDegree() > 0 && getMaxParseOrder() > 0) {
// ensure at least the (0, 0) element is properly set
if (Precision.equals(container.c[container.flattener.index(0, 0)], 0.0, 0)) {
container.c[container.flattener.index(0, 0)] = 1.0;
}
}
if (!(okFields && maxDegree >= 0)) {
String loaderName = getClass().getName();
loaderName = loaderName.substring(loaderName.lastIndexOf('.') + 1);
throw new OrekitException(OrekitMessages.UNEXPECTED_FILE_FORMAT_ERROR_FOR_LOADER,
name, loaderName);
}
container = container.resize(maxDegree, maxOrder);
setRawCoefficients(true, container.flattener, container.c, container.s, name);
setReadComplete(true);
}
/** Get a provider for read spherical harmonics coefficients.
* <p>
* EGM fields don't include time-dependent parts, so this method returns
* directly a constant 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) {
return getBaseProvider(wantNormalized, degree, order);
}
/** Temporary container for reading coefficients.
* @since 11.1
*/
private static class Container {
/** Converter from triangular to flat form. */
private final Flattener flattener;
/** Cosine coefficients. */
private final double[] c;
/** Sine coefficients. */
private final double[] s;
/** Initial value for coefficients. */
private final double initialValue;
/** Build a container with given degree and order.
* @param degree degree of the container
* @param order order of the container
* @param initialValue initial value for coefficients
*/
Container(final int degree, final int order, final double initialValue) {
this.flattener = new Flattener(degree, order);
this.c = new double[flattener.arraySize()];
this.s = new double[flattener.arraySize()];
this.initialValue = initialValue;
Arrays.fill(c, initialValue);
Arrays.fill(s, initialValue);
}
/** Build a resized container.
* @param degree degree of the resized container
* @param order order of the resized container
* @return resized container
*/
Container resize(final int degree, final int order) {
final Container resized = new Container(degree, order, initialValue);
for (int n = 0; n <= degree; ++n) {
for (int m = 0; m <= FastMath.min(n, order); ++m) {
if (flattener.withinRange(n, m)) {
final int rIndex = resized.flattener.index(n, m);
final int index = flattener.index(n, m);
resized.c[rIndex] = c[index];
resized.s[rIndex] = s[index];
}
}
}
return resized;
}
}
}