/* Copyright 2002-2017 CS Systèmes d'Information
* Licensed to CS Systèmes d'Information (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.estimation.measurements;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import org.hipparchus.stat.descriptive.moment.Mean;
import org.hipparchus.stat.descriptive.rank.Max;
import org.hipparchus.stat.descriptive.rank.Median;
import org.hipparchus.stat.descriptive.rank.Min;
import org.hipparchus.util.FastMath;
import org.junit.Assert;
import org.junit.Test;
import org.orekit.errors.OrekitException;
import org.orekit.estimation.Context;
import org.orekit.estimation.EstimationTestUtils;
import org.orekit.estimation.EstimationUtils;
import org.orekit.estimation.ParameterFunction;
import org.orekit.estimation.StateFunction;
import org.orekit.estimation.measurements.modifiers.RangeTroposphericDelayModifier;
import org.orekit.models.earth.SaastamoinenModel;
import org.orekit.orbits.OrbitType;
import org.orekit.orbits.PositionAngle;
import org.orekit.propagation.Propagator;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.conversion.NumericalPropagatorBuilder;
import org.orekit.propagation.sampling.OrekitStepInterpolator;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.ChronologicalComparator;
import org.orekit.utils.Constants;
import org.orekit.utils.ParameterDriver;
public class RangeTest {
/**
* Test the values of the range comparing the observed values and the estimated values
* Both are calculated with a different algorithm
* @throws OrekitException
*/
@Test
public void testValues() throws OrekitException {
boolean printResults = false;
if (printResults) {
System.out.println("\nTest Range Values\n");
}
// Run test
this.genericTestValues(printResults);
}
/**
* Test the values of the state derivatives using a numerical
* finite differences calculation as a reference
* @throws OrekitException
*/
@Test
public void testStateDerivatives() throws OrekitException {
boolean printResults = false;
if (printResults) {
System.out.println("\nTest Range State Derivatives - Finite Differences Comparison\n");
}
// Run test
boolean isModifier = false;
this.genericTestStateDerivatives(isModifier, printResults);
}
/**
* Test the values of the state derivatives with modifier using a numerical
* finite differences calculation as a reference
* @throws OrekitException
*/
@Test
public void testStateDerivativesWithModifier() throws OrekitException {
boolean printResults = false;
if (printResults) {
System.out.println("\nTest Range State Derivatives with Modifier - Finite Differences Comparison\n");
}
// Run test
boolean isModifier = true;
this.genericTestStateDerivatives(isModifier, printResults);
}
/**
* Test the values of the parameters' derivatives using a numerical
* finite differences calculation as a reference
* @throws OrekitException
*/
@Test
public void testParameterDerivatives() throws OrekitException {
// Print the results ?
boolean printResults = false;
if (printResults) {
System.out.println("\nTest Range Parameter Derivatives - Finite Differences Comparison\n");
}
// Run test
boolean isModifier = false;
this.genericTestParameterDerivatives(isModifier, printResults);
}
/**
* Test the values of the parameters' derivatives with modifier, using a numerical
* finite differences calculation as a reference
* @throws OrekitException
*/
@Test
public void testParameterDerivativesWithModifier() throws OrekitException {
// Print the results ?
boolean printResults = false;
if (printResults) {
System.out.println("\nTest Range Parameter Derivatives with Modifier - Finite Differences Comparison\n");
}
// Run test
boolean isModifier = true;
this.genericTestParameterDerivatives(isModifier, printResults);
}
/**
* Generic test function for values of the range
* @param printResults Print the results ?
* @throws OrekitException
*/
void genericTestValues(final boolean printResults)
throws OrekitException {
Context context = EstimationTestUtils.eccentricContext();
final NumericalPropagatorBuilder propagatorBuilder =
context.createBuilder(OrbitType.KEPLERIAN, PositionAngle.TRUE, true,
1.0e-6, 60.0, 0.001);
// Create perfect range measurements
final Propagator propagator = EstimationTestUtils.createPropagator(context.initialOrbit,
propagatorBuilder);
final List<ObservedMeasurement<?>> measurements =
EstimationTestUtils.createMeasurements(propagator,
new RangeMeasurementCreator(context),
1.0, 3.0, 300.0);
// Lists for results' storage - Used only for derivatives with respect to state
// "final" value to be seen by "handleStep" function of the propagator
final List<Double> absoluteErrors = new ArrayList<Double>();
final List<Double> relativeErrors = new ArrayList<Double>();
// Set master mode
// Use a lambda function to implement "handleStep" function
propagator.setMasterMode((OrekitStepInterpolator interpolator, boolean isLast) -> {
for (final ObservedMeasurement<?> measurement : measurements) {
// Play test if the measurement date is between interpolator previous and current date
if ((measurement.getDate().durationFrom(interpolator.getPreviousState().getDate()) > 0.) &&
(measurement.getDate().durationFrom(interpolator.getCurrentState().getDate()) <= 0.)
) {
// We intentionally propagate to a date which is close to the
// real spacecraft state but is *not* the accurate date, by
// compensating only part of the downlink delay. This is done
// in order to validate the partial derivatives with respect
// to velocity. If we had chosen the proper state date, the
// range would have depended only on the current position but
// not on the current velocity.
final double meanDelay = measurement.getObservedValue()[0] / Constants.SPEED_OF_LIGHT;
final AbsoluteDate date = measurement.getDate().shiftedBy(-0.75 * meanDelay);
final SpacecraftState state = interpolator.getInterpolatedState(date);
// Values of the Range & errors
final double RangeObserved = measurement.getObservedValue()[0];
final double RangeEstimated = measurement.estimate(0, 0, state).getEstimatedValue()[0];
final double absoluteError = RangeEstimated-RangeObserved;
absoluteErrors.add(absoluteError);
relativeErrors.add(FastMath.abs(absoluteError)/FastMath.abs(RangeObserved));
// Print results on console ?
if (printResults) {
final AbsoluteDate measurementDate = measurement.getDate();
String stationName = ((Range) measurement).getStation().getBaseFrame().getName();
System.out.format(Locale.US, "%-15s %-23s %-23s %19.6f %19.6f %13.6e %13.6e%n",
stationName, measurementDate, date,
RangeObserved, RangeEstimated,
FastMath.abs(RangeEstimated-RangeObserved),
FastMath.abs((RangeEstimated-RangeObserved)/RangeObserved));
}
} // End if measurement date between previous and current interpolator step
} // End for loop on the measurements
}); // End lambda function handlestep
// Print results on console ? Header
if (printResults) {
System.out.format(Locale.US, "%-15s %-23s %-23s %19s %19s %13s %13s%n",
"Station","Measurement Date","State Date",
"Range observed [m]","Range estimated [m]",
"ΔRange [m]","rel ΔRange");
}
// Rewind the propagator to initial date
propagator.propagate(context.initialOrbit.getDate());
// Sort measurements chronologically
measurements.sort(new ChronologicalComparator());
// Propagate to final measurement's date
propagator.propagate(measurements.get(measurements.size()-1).getDate());
// Convert lists to double array
final double[] absErrors = absoluteErrors.stream().mapToDouble(Double::doubleValue).toArray();
final double[] relErrors = relativeErrors.stream().mapToDouble(Double::doubleValue).toArray();
// Statistics' assertion
final double absErrorsMedian = new Median().evaluate(absErrors);
final double absErrorsMin = new Min().evaluate(absErrors);
final double absErrorsMax = new Max().evaluate(absErrors);
final double relErrorsMedian = new Median().evaluate(relErrors);
final double relErrorsMax = new Max().evaluate(relErrors);
// Print the results on console ? Final results
if (printResults) {
System.out.println();
System.out.println("Absolute errors median: " + absErrorsMedian);
System.out.println("Absolute errors min : " + absErrorsMin);
System.out.println("Absolute errors max : " + absErrorsMax);
System.out.println("Relative errors median: " + relErrorsMedian);
System.out.println("Relative errors max : " + relErrorsMax);
}
Assert.assertEquals(0.0, absErrorsMedian, 1e-8);
Assert.assertEquals(0.0, absErrorsMin, 2e-7);
Assert.assertEquals(0.0, absErrorsMax, 2e-7);
Assert.assertEquals(0.0, relErrorsMedian, 1e-14);
Assert.assertEquals(0.0, relErrorsMax, 2e-14);
}
/**
* Generic test function for derivatives with respect to state
* @param isModifier Use of atmospheric modifiers
* @param printResults Print the results ?
* @throws OrekitException
*/
void genericTestStateDerivatives(final boolean isModifier, final boolean printResults)
throws OrekitException {
Context context = EstimationTestUtils.eccentricContext();
final NumericalPropagatorBuilder propagatorBuilder =
context.createBuilder(OrbitType.KEPLERIAN, PositionAngle.TRUE, true,
1.0e-6, 60.0, 0.001);
// Create perfect range measurements
final Propagator propagator = EstimationTestUtils.createPropagator(context.initialOrbit,
propagatorBuilder);
final List<ObservedMeasurement<?>> measurements =
EstimationTestUtils.createMeasurements(propagator,
new RangeMeasurementCreator(context),
1.0, 3.0, 300.0);
// Lists for results' storage - Used only for derivatives with respect to state
// "final" value to be seen by "handleStep" function of the propagator
final List<Double> errorsP = new ArrayList<Double>();
final List<Double> errorsV = new ArrayList<Double>();
// Set master mode
// Use a lambda function to implement "handleStep" function
propagator.setMasterMode((OrekitStepInterpolator interpolator, boolean isLast) -> {
for (final ObservedMeasurement<?> measurement : measurements) {
// Play test if the measurement date is between interpolator previous and current date
if ((measurement.getDate().durationFrom(interpolator.getPreviousState().getDate()) > 0.) &&
(measurement.getDate().durationFrom(interpolator.getCurrentState().getDate()) <= 0.)
) {
// Add modifiers if test implies it
final RangeTroposphericDelayModifier modifier = new RangeTroposphericDelayModifier(SaastamoinenModel.getStandardModel());
if (isModifier) {
((Range) measurement).addModifier(modifier);
}
// We intentionally propagate to a date which is close to the
// real spacecraft state but is *not* the accurate date, by
// compensating only part of the downlink delay. This is done
// in order to validate the partial derivatives with respect
// to velocity. If we had chosen the proper state date, the
// range would have depended only on the current position but
// not on the current velocity.
final double meanDelay = measurement.getObservedValue()[0] / Constants.SPEED_OF_LIGHT;
final AbsoluteDate date = measurement.getDate().shiftedBy(-0.75 * meanDelay);
final SpacecraftState state = interpolator.getInterpolatedState(date);
final double[][] jacobian = measurement.estimate(0, 0, state).getStateDerivatives();
// Jacobian reference value
final double[][] jacobianRef;
// Compute a reference value using finite differences
jacobianRef = EstimationUtils.differentiate(new StateFunction() {
public double[] value(final SpacecraftState state) throws OrekitException {
return measurement.estimate(0, 0, state).getEstimatedValue();
}
}, measurement.getDimension(), OrbitType.CARTESIAN, PositionAngle.TRUE, 1.0, 3).value(state);
Assert.assertEquals(jacobianRef.length, jacobian.length);
Assert.assertEquals(jacobianRef[0].length, jacobian[0].length);
// Errors & relative errors on the jacobian
double [][] dJacobian = new double[jacobian.length][jacobian[0].length];
double [][] dJacobianRelative = new double[jacobian.length][jacobian[0].length];
for (int i = 0; i < jacobian.length; ++i) {
for (int j = 0; j < jacobian[i].length; ++j) {
dJacobian[i][j] = jacobian[i][j] - jacobianRef[i][j];
dJacobianRelative[i][j] = FastMath.abs(dJacobian[i][j]/jacobianRef[i][j]);
if (j < 3) { errorsP.add(dJacobianRelative[i][j]);
} else { errorsV.add(dJacobianRelative[i][j]); }
}
}
// Print values in console ?
if (printResults) {
String stationName = ((Range) measurement).getStation().getBaseFrame().getName();
System.out.format(Locale.US, "%-15s %-23s %-23s " +
"%10.3e %10.3e %10.3e " +
"%10.3e %10.3e %10.3e " +
"%10.3e %10.3e %10.3e " +
"%10.3e %10.3e %10.3e%n",
stationName, measurement.getDate(), date,
dJacobian[0][0],dJacobian[0][1],dJacobian[0][2],
dJacobian[0][3],dJacobian[0][4],dJacobian[0][5],
dJacobianRelative[0][0],dJacobianRelative[0][1],dJacobianRelative[0][2],
dJacobianRelative[0][3],dJacobianRelative[0][4],dJacobianRelative[0][5]);
}
} // End if measurement date between previous and current interpolator step
} // End for loop on the measurements
});
// Print results on console ?
if (printResults) {
System.out.format(Locale.US, "%-15s %-23s %-23s " +
"%10s %10s %10s " +
"%10s %10s %10s " +
"%10s %10s %10s " +
"%10s %10s %10s%n",
"Station","Measurement Date","State Date",
"ΔdPx","ΔdPy","ΔdPz","ΔdVx","ΔdVy","ΔdVz",
"rel ΔdPx","rel ΔdPy","rel ΔdPz",
"rel ΔdVx","rel ΔdVy","rel ΔdVz");
}
// Rewind the propagator to initial date
propagator.propagate(context.initialOrbit.getDate());
// Sort measurements chronologically
measurements.sort(new ChronologicalComparator());
// Propagate to final measurement's date
propagator.propagate(measurements.get(measurements.size()-1).getDate());
// Convert lists to double[] and evaluate some statistics
final double relErrorsP[] = errorsP.stream().mapToDouble(Double::doubleValue).toArray();
final double relErrorsV[] = errorsV.stream().mapToDouble(Double::doubleValue).toArray();
final double errorsPMedian = new Median().evaluate(relErrorsP);
final double errorsPMean = new Mean().evaluate(relErrorsP);
final double errorsPMax = new Max().evaluate(relErrorsP);
final double errorsVMedian = new Median().evaluate(relErrorsV);
final double errorsVMean = new Mean().evaluate(relErrorsV);
final double errorsVMax = new Max().evaluate(relErrorsV);
// Print the results on console ?
if (printResults) {
System.out.println();
System.out.format(Locale.US,"Relative errors dR/dP -> Median: %6.3e / Mean: %6.3e / Max: %6.3e%n",
errorsPMedian, errorsPMean, errorsPMax);
System.out.format(Locale.US,"Relative errors dR/dV -> Median: %6.3e / Mean: %6.3e / Max: %6.3e%n",
errorsVMedian, errorsVMean, errorsVMax);
}
// Assert the results / max values depend on the test
double refErrorsPMedian, refErrorsPMean, refErrorsPMax;
double refErrorsVMedian, refErrorsVMean, refErrorsVMax;
// Finite differences reference values
refErrorsPMedian = 1.2e-09;
refErrorsPMean = 8.1e-09;
refErrorsPMax = 3.6e-07;
refErrorsVMedian = 3.1e-04;
refErrorsVMean = 1.7e-03;
refErrorsVMax = 8.1e-02;
Assert.assertEquals(0.0, errorsPMedian, refErrorsPMedian);
Assert.assertEquals(0.0, errorsPMean, refErrorsPMean);
Assert.assertEquals(0.0, errorsPMax, refErrorsPMax);
Assert.assertEquals(0.0, errorsVMedian, refErrorsVMedian);
Assert.assertEquals(0.0, errorsVMean, refErrorsVMean);
Assert.assertEquals(0.0, errorsVMax, refErrorsVMax);
}
/**
* Generic test function for derivatives with respect to parameters (station's position in station's topocentric frame)
* @param isModifier Use of atmospheric modifiers
* @param printResults Print the results ?
* @throws OrekitException
*/
void genericTestParameterDerivatives(final boolean isModifier, final boolean printResults)
throws OrekitException {
Context context = EstimationTestUtils.eccentricContext();
final NumericalPropagatorBuilder propagatorBuilder =
context.createBuilder(OrbitType.KEPLERIAN, PositionAngle.TRUE, true,
1.0e-6, 60.0, 0.001);
// Create perfect range measurements
for (final GroundStation station : context.stations) {
station.getEastOffsetDriver().setSelected(true);
station.getNorthOffsetDriver().setSelected(true);
station.getZenithOffsetDriver().setSelected(true);
}
final Propagator propagator = EstimationTestUtils.createPropagator(context.initialOrbit,
propagatorBuilder);
final List<ObservedMeasurement<?>> measurements =
EstimationTestUtils.createMeasurements(propagator,
new RangeMeasurementCreator(context),
1.0, 3.0, 300.0);
// List to store the results
final List<Double> relErrorList = new ArrayList<Double>();
// Set master mode
// Use a lambda function to implement "handleStep" function
propagator.setMasterMode((OrekitStepInterpolator interpolator, boolean isLast) -> {
for (final ObservedMeasurement<?> measurement : measurements) {
// Play test if the measurement date is between interpolator previous and current date
if ((measurement.getDate().durationFrom(interpolator.getPreviousState().getDate()) > 0.) &&
(measurement.getDate().durationFrom(interpolator.getCurrentState().getDate()) <= 0.)
) {
// Add modifiers if test implies it
final RangeTroposphericDelayModifier modifier = new RangeTroposphericDelayModifier(SaastamoinenModel.getStandardModel());
if (isModifier) {
((Range) measurement).addModifier(modifier);
}
// Parameter corresponding to station position offset
final GroundStation stationParameter = ((Range) measurement).getStation();
// We intentionally propagate to a date which is close to the
// real spacecraft state but is *not* the accurate date, by
// compensating only part of the downlink delay. This is done
// in order to validate the partial derivatives with respect
// to velocity. If we had chosen the proper state date, the
// range would have depended only on the current position but
// not on the current velocity.
final double meanDelay = measurement.getObservedValue()[0] / Constants.SPEED_OF_LIGHT;
final AbsoluteDate date = measurement.getDate().shiftedBy(-0.75 * meanDelay);
final SpacecraftState state = interpolator.getInterpolatedState(date);
final ParameterDriver[] drivers = new ParameterDriver[] {
stationParameter.getEastOffsetDriver(),
stationParameter.getNorthOffsetDriver(),
stationParameter.getZenithOffsetDriver()
};
if (printResults) {
String stationName = ((Range) measurement).getStation().getBaseFrame().getName();
System.out.format(Locale.US, "%-15s %-23s %-23s ",
stationName, measurement.getDate(), date);
}
for (int i = 0; i < 3; ++i) {
final double[] gradient = measurement.estimate(0, 0, state).getParameterDerivatives(drivers[i]);
Assert.assertEquals(1, measurement.getDimension());
Assert.assertEquals(1, gradient.length);
// Compute a reference value using finite differences
final ParameterFunction dMkdP =
EstimationUtils.differentiate(new ParameterFunction() {
/** {@inheritDoc} */
@Override
public double value(final ParameterDriver parameterDriver) throws OrekitException {
return measurement.estimate(0, 0, state).getEstimatedValue()[0];
}
}, drivers[i], 3, 20.0);
final double ref = dMkdP.value(drivers[i]);
if (printResults) {
System.out.format(Locale.US,"%10.3e %10.3e ",gradient[0]-ref,FastMath.abs((gradient[0]-ref)/ref));
}
final double relError = FastMath.abs((ref-gradient[0])/ref);
relErrorList.add(relError);
// Assert.assertEquals(ref, gradient[0], 6.1e-5 * FastMath.abs(ref));
}
if (printResults) {
System.out.format(Locale.US,"%n");
}
} // End if measurement date between previous and current interpolator step
} // End for loop on the measurements
});
// Rewind the propagator to initial date
propagator.propagate(context.initialOrbit.getDate());
// Sort measurements chronologically
measurements.sort(new ChronologicalComparator());
// Print results ? Header
if (printResults) {
System.out.format(Locale.US, "%-15s %-23s %-23s " +
"%10s %10s %10s " +
"%10s %10s %10s%n",
"Station","Measurement Date","State Date",
"ΔdQx","rel ΔdQx",
"ΔdQy","rel ΔdQy",
"ΔdQz","rel ΔdQz");
}
// Propagate to final measurement's date
propagator.propagate(measurements.get(measurements.size()-1).getDate());
// Convert error list to double[]
final double relErrors[] = relErrorList.stream().mapToDouble(Double::doubleValue).toArray();
// Compute statistics
final double relErrorsMedian = new Median().evaluate(relErrors);
final double relErrorsMean = new Mean().evaluate(relErrors);
final double relErrorsMax = new Max().evaluate(relErrors);
// Print the results on console ?
if (printResults) {
System.out.println();
System.out.format(Locale.US,"Relative errors dR/dQ -> Median: %6.3e / Mean: %6.3e / Max: %6.3e%n",
relErrorsMedian, relErrorsMean, relErrorsMax);
}
// Assert the results / max values depend on the test
double refErrorsMedian, refErrorsMean, refErrorsMax;
// Numeric references
refErrorsMedian = 8.7e-11;
refErrorsMean = 3.4e-10;
refErrorsMax = 1.3e-08;
Assert.assertEquals(0.0, relErrorsMedian, refErrorsMedian);
Assert.assertEquals(0.0, relErrorsMean, refErrorsMean);
Assert.assertEquals(0.0, relErrorsMax, refErrorsMax);
}
}