PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator.java
/*
* Copyright (C) 2020 Alberto Irurueta Carro (alberto@irurueta.com)
*
* Licensed 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 com.irurueta.navigation.inertial.calibration.magnetometer;
import com.irurueta.algebra.Matrix;
import com.irurueta.navigation.LockedException;
import com.irurueta.navigation.NotReadyException;
import com.irurueta.navigation.inertial.calibration.CalibrationException;
import com.irurueta.navigation.inertial.calibration.StandardDeviationFrameBodyMagneticFluxDensity;
import com.irurueta.numerical.robust.PROMedSRobustEstimator;
import com.irurueta.numerical.robust.PROMedSRobustEstimatorListener;
import com.irurueta.numerical.robust.RobustEstimator;
import com.irurueta.numerical.robust.RobustEstimatorException;
import com.irurueta.numerical.robust.RobustEstimatorMethod;
import java.io.IOException;
import java.util.List;
/**
* Robustly estimates magnetometer soft-iron cross
* couplings and scaling factors using PROMedS algorithm.
* <p>
* To use this calibrator at least 4 measurements at different known
* frames must be provided. In other words, magnetometer samples must
* be obtained at 4 different positions or orientations.
* Notice that frame velocities are ignored by this calibrator.
* <p>
* Measured magnetic flux density is assumed to follow the model shown below:
* <pre>
* mBmeas = bm + (I + Mm) * mBtrue + w
* </pre>
* Where:
* - mBmeas is the measured magnetic flux density. This is a 3x1 vector.
* - bm is magnetometer hard-iron bias. Ideally, on a perfect magnetometer,
* this should be a 3x1 zero vector.
* - I is the 3x3 identity matrix.
* - Mm is the 3x3 soft-iron matrix containing cross-couplings and scaling
* factors. Ideally, on a perfect magnetometer, this should be a 3x3 zero
* matrix.
* - mBtrue is ground-truth magnetic flux density. This is a 3x1 vector.
* - w is measurement noise. This is a 3x1 vector.
*/
public class PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator extends
RobustKnownHardIronAndFrameMagnetometerCalibrator {
/**
* Default value to be used for stop threshold. Stop threshold can be used to
* avoid keeping the algorithm unnecessarily iterating in case that best
* estimated threshold using median of residuals is not small enough. Once a
* solution is found that generates a threshold below this value, the
* algorithm will stop.
* The stop threshold can be used to prevent the LMedS algorithm iterating
* too many times in cases where samples have a very similar accuracy.
* For instance, in cases where proportion of outliers is very small (close
* to 0%), and samples are very accurate (i.e. 1e-6), the algorithm would
* iterate for a long time trying to find the best solution when indeed
* there is no need to do that if a reasonable threshold has already been
* reached.
* Because of this behaviour the stop threshold can be set to a value much
* lower than the one typically used in RANSAC, and yet the algorithm could
* still produce even smaller thresholds in estimated results.
*/
public static final double DEFAULT_STOP_THRESHOLD = 500e-9;
/**
* Minimum allowed stop threshold value.
*/
public static final double MIN_STOP_THRESHOLD = 0.0;
/**
* Threshold to be used to keep the algorithm iterating in case that best
* estimated threshold using median of residuals is not small enough. Once
* a solution is found that generates a threshold below this value, the
* algorithm will stop.
* The stop threshold can be used to prevent the LMedS algorithm iterating
* too many times in cases where samples have a very similar accuracy.
* For instance, in cases where proportion of outliers is very small (close
* to 0%), and samples are very accurate (i.e. 1e-6), the algorithm would
* iterate for a long time trying to find the best solution when indeed
* there is no need to do that if a reasonable threshold has already been
* reached.
* Because of this behaviour the stop threshold can be set to a value much
* lower than the one typically used in RANSAC, and yet the algorithm could
* still produce even smaller thresholds in estimated results.
*/
private double stopThreshold = DEFAULT_STOP_THRESHOLD;
/**
* Quality scores corresponding to each provided sample.
* The larger the score value the better the quality of the sample.
*/
private double[] qualityScores;
/**
* Constructor.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator() {
}
/**
* Constructor.
*
* @param listener listener to be notified of events such as when estimation
* starts, ends or its progress significantly changes.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final RobustKnownHardIronAndFrameMagnetometerCalibratorListener listener) {
super(listener);
}
/**
* Constructor.
*
* @param measurements list of body magnetic flux density measurements with standard
* deviations taken at different frames (positions and
* orientations).
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final List<StandardDeviationFrameBodyMagneticFluxDensity> measurements) {
super(measurements);
}
/**
* Constructor.
*
* @param measurements list of body magnetic flux density measurements with standard
* deviations taken at different frames (positions and
* orientations).
* @param listener listener to handle events raised by this calibrator.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final List<StandardDeviationFrameBodyMagneticFluxDensity> measurements,
final RobustKnownHardIronAndFrameMagnetometerCalibratorListener listener) {
super(measurements, listener);
}
/**
* Constructor.
*
* @param commonAxisUsed indicates whether z-axis is assumed to be common
* for the accelerometer, gyroscope and magnetometer.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(final boolean commonAxisUsed) {
super(commonAxisUsed);
}
/**
* Constructor.
*
* @param commonAxisUsed indicates whether z-axis is assumed to be common
* for the accelerometer, gyroscope and magnetometer.
* @param listener listener to handle events raised by this calibrator.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final boolean commonAxisUsed, final RobustKnownHardIronAndFrameMagnetometerCalibratorListener listener) {
super(commonAxisUsed, listener);
}
/**
* Constructor.
*
* @param measurements list of body magnetic flux density measurements with standard
* deviations taken at different frames (positions and
* orientations).
* @param commonAxisUsed indicates whether z-axis is assumed to be common
* for the accelerometer, gyroscope and magnetometer.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final List<StandardDeviationFrameBodyMagneticFluxDensity> measurements, final boolean commonAxisUsed) {
super(measurements, commonAxisUsed);
}
/**
* Constructor.
*
* @param measurements list of body magnetic flux density measurements with standard
* deviations taken at different frames (positions and
* orientations).
* @param commonAxisUsed indicates whether z-axis is assumed to be common
* for the accelerometer, gyroscope and magnetometer.
* @param listener listener to handle events raised by this calibrator.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final List<StandardDeviationFrameBodyMagneticFluxDensity> measurements, final boolean commonAxisUsed,
final RobustKnownHardIronAndFrameMagnetometerCalibratorListener listener) {
super(measurements, commonAxisUsed, listener);
}
/**
* Constructor.
*
* @param qualityScores quality scores corresponding to each provided
* measurement. The larger the score value the better
* the quality of the sample.
* @throws IllegalArgumentException if provided quality scores length
* is smaller than 3 samples.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(final double[] qualityScores) {
super();
internalSetQualityScores(qualityScores);
}
/**
* Constructor.
*
* @param qualityScores quality scores corresponding to each provided
* measurement. The larger the score value the better
* the quality of the sample.
* @param listener listener to be notified of events such as when estimation
* starts, ends or its progress significantly changes.
* @throws IllegalArgumentException if provided quality scores length
* is smaller than 3 samples.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final double[] qualityScores, final RobustKnownHardIronAndFrameMagnetometerCalibratorListener listener) {
super(listener);
internalSetQualityScores(qualityScores);
}
/**
* Constructor.
*
* @param qualityScores quality scores corresponding to each provided
* measurement. The larger the score value the better
* the quality of the sample.
* @param measurements list of body magnetic flux density measurements with standard
* deviations taken at different frames (positions and
* orientations).
* @throws IllegalArgumentException if provided quality scores length
* is smaller than 3 samples.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final double[] qualityScores, final List<StandardDeviationFrameBodyMagneticFluxDensity> measurements) {
super(measurements);
internalSetQualityScores(qualityScores);
}
/**
* Constructor.
*
* @param qualityScores quality scores corresponding to each provided
* measurement. The larger the score value the better
* the quality of the sample.
* @param measurements list of body magnetic flux density measurements with standard
* deviations taken at different frames (positions and
* orientations).
* @param listener listener to handle events raised by this calibrator.
* @throws IllegalArgumentException if provided quality scores length
* is smaller than 3 samples.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final double[] qualityScores, final List<StandardDeviationFrameBodyMagneticFluxDensity> measurements,
final RobustKnownHardIronAndFrameMagnetometerCalibratorListener listener) {
super(measurements, listener);
internalSetQualityScores(qualityScores);
}
/**
* Constructor.
*
* @param qualityScores quality scores corresponding to each provided
* measurement. The larger the score value the better
* the quality of the sample.
* @param commonAxisUsed indicates whether z-axis is assumed to be common
* for the accelerometer, gyroscope and magnetometer.
* @throws IllegalArgumentException if provided quality scores length
* is smaller than 3 samples.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final double[] qualityScores, final boolean commonAxisUsed) {
super(commonAxisUsed);
internalSetQualityScores(qualityScores);
}
/**
* Constructor.
*
* @param qualityScores quality scores corresponding to each provided
* measurement. The larger the score value the better
* the quality of the sample.
* @param commonAxisUsed indicates whether z-axis is assumed to be common
* for the accelerometer, gyroscope and magnetometer.
* @param listener listener to handle events raised by this calibrator.
* @throws IllegalArgumentException if provided quality scores length
* is smaller than 3 samples.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final double[] qualityScores, final boolean commonAxisUsed,
final RobustKnownHardIronAndFrameMagnetometerCalibratorListener listener) {
super(commonAxisUsed, listener);
internalSetQualityScores(qualityScores);
}
/**
* Constructor.
*
* @param qualityScores quality scores corresponding to each provided
* measurement. The larger the score value the better
* the quality of the sample.
* @param measurements list of body magnetic flux density measurements with standard
* deviations taken at different frames (positions and
* orientations).
* @param commonAxisUsed indicates whether z-axis is assumed to be common
* for the accelerometer, gyroscope and magnetometer.
* @throws IllegalArgumentException if provided quality scores length
* is smaller than 3 samples.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final double[] qualityScores, final List<StandardDeviationFrameBodyMagneticFluxDensity> measurements,
final boolean commonAxisUsed) {
super(measurements, commonAxisUsed);
internalSetQualityScores(qualityScores);
}
/**
* Constructor.
*
* @param qualityScores quality scores corresponding to each provided
* measurement. The larger the score value the better
* the quality of the sample.
* @param measurements list of body magnetic flux density measurements with standard
* deviations taken at different frames (positions and
* orientations).
* @param commonAxisUsed indicates whether z-axis is assumed to be common
* for the accelerometer, gyroscope and magnetometer.
* @param listener listener to handle events raised by this calibrator.
* @throws IllegalArgumentException if provided quality scores length
* is smaller than 3 samples.
*/
public PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator(
final double[] qualityScores, final List<StandardDeviationFrameBodyMagneticFluxDensity> measurements,
final boolean commonAxisUsed, final RobustKnownHardIronAndFrameMagnetometerCalibratorListener listener) {
super(measurements, commonAxisUsed, listener);
internalSetQualityScores(qualityScores);
}
/**
* Returns threshold to be used to keep the algorithm iterating in case that
* best estimated threshold using median of residuals is not small enough.
* Once a solution is found that generates a threshold below this value, the
* algorithm will stop.
* The stop threshold can be used to prevent the LMedS algorithm to iterate
* too many times in cases where samples have a very similar accuracy.
* For instance, in cases where proportion of outliers is very small (close
* to 0%), and samples are very accurate (i.e. 1e-6), the algorithm would
* iterate for a long time trying to find the best solution when indeed
* there is no need to do that if a reasonable threshold has already been
* reached.
* Because of this behaviour the stop threshold can be set to a value much
* lower than the one typically used in RANSAC, and yet the algorithm could
* still produce even smaller thresholds in estimated results.
*
* @return stop threshold to stop the algorithm prematurely when a certain
* accuracy has been reached.
*/
public double getStopThreshold() {
return stopThreshold;
}
/**
* Sets threshold to be used to keep the algorithm iterating in case that
* best estimated threshold using median of residuals is not small enough.
* Once a solution is found that generates a threshold below this value,
* the algorithm will stop.
* The stop threshold can be used to prevent the LMedS algorithm to iterate
* too many times in cases where samples have a very similar accuracy.
* For instance, in cases where proportion of outliers is very small (close
* to 0%), and samples are very accurate (i.e. 1e-6), the algorithm would
* iterate for a long time trying to find the best solution when indeed
* there is no need to do that if a reasonable threshold has already been
* reached.
* Because of this behaviour the stop threshold can be set to a value much
* lower than the one typically used in RANSAC, and yet the algorithm could
* still produce even smaller thresholds in estimated results.
*
* @param stopThreshold stop threshold to stop the algorithm prematurely
* when a certain accuracy has been reached.
* @throws IllegalArgumentException if provided value is zero or negative.
* @throws LockedException if calibrator is currently running.
*/
public void setStopThreshold(final double stopThreshold) throws LockedException {
if (running) {
throw new LockedException();
}
if (stopThreshold <= MIN_STOP_THRESHOLD) {
throw new IllegalArgumentException();
}
this.stopThreshold = stopThreshold;
}
/**
* Returns quality scores corresponding to each provided sample.
* The larger the score value the better the quality of the sample.
*
* @return quality scores corresponding to each sample.
*/
@Override
public double[] getQualityScores() {
return qualityScores;
}
/**
* Sets quality scores corresponding to each provided sample.
* The larger the score value the better the quality of the sample.
*
* @param qualityScores quality scores corresponding to each sample.
* @throws IllegalArgumentException if provided quality scores length
* is smaller than minimum required samples.
* @throws LockedException if calibrator is currently running.
*/
@Override
public void setQualityScores(final double[] qualityScores) throws LockedException {
if (running) {
throw new LockedException();
}
internalSetQualityScores(qualityScores);
}
/**
* Indicates whether solver is ready to find a solution.
*
* @return true if solver is ready, false otherwise.
*/
@Override
public boolean isReady() {
return super.isReady() && qualityScores != null && qualityScores.length == measurements.size();
}
/**
* Estimates magnetometer calibration parameters containing soft-iron
* scale factors and cross-coupling errors.
*
* @throws LockedException if calibrator is currently running.
* @throws NotReadyException if calibrator is not ready.
* @throws CalibrationException if estimation fails for numerical reasons.
*/
@SuppressWarnings("DuplicatedCode")
@Override
public void calibrate() throws LockedException, NotReadyException, CalibrationException {
if (running) {
throw new LockedException();
}
if (!isReady()) {
throw new NotReadyException();
}
final var innerEstimator = new PROMedSRobustEstimator<>(new PROMedSRobustEstimatorListener<Matrix>() {
@Override
public double[] getQualityScores() {
return qualityScores;
}
@Override
public double getThreshold() {
return stopThreshold;
}
@Override
public int getTotalSamples() {
return measurements.size();
}
@Override
public int getSubsetSize() {
return preliminarySubsetSize;
}
@Override
public void estimatePreliminarSolutions(final int[] samplesIndices, final List<Matrix> solutions) {
computePreliminarySolutions(samplesIndices, solutions);
}
@Override
public double computeResidual(final Matrix currentEstimation, final int i) {
return computeError(measurements.get(i), currentEstimation);
}
@Override
public boolean isReady() {
return PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator.this.isReady();
}
@Override
public void onEstimateStart(final RobustEstimator<Matrix> estimator) {
// no action needed
}
@Override
public void onEstimateEnd(final RobustEstimator<Matrix> estimator) {
// no action needed
}
@Override
public void onEstimateNextIteration(final RobustEstimator<Matrix> estimator, final int iteration) {
if (listener != null) {
listener.onCalibrateNextIteration(
PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator.this, iteration);
}
}
@Override
public void onEstimateProgressChange(final RobustEstimator<Matrix> estimator, final float progress) {
if (listener != null) {
listener.onCalibrateProgressChange(
PROMedSRobustKnownHardIronAndFrameMagnetometerCalibrator.this, progress);
}
}
});
try {
running = true;
if (listener != null) {
listener.onCalibrateStart(this);
}
inliersData = null;
setupWmmEstimator();
innerEstimator.setUseInlierThresholds(true);
innerEstimator.setConfidence(confidence);
innerEstimator.setMaxIterations(maxIterations);
innerEstimator.setProgressDelta(progressDelta);
final var preliminaryResult = innerEstimator.estimate();
inliersData = innerEstimator.getInliersData();
attemptRefine(preliminaryResult);
if (listener != null) {
listener.onCalibrateEnd(this);
}
} catch (final com.irurueta.numerical.LockedException e) {
throw new LockedException(e);
} catch (final com.irurueta.numerical.NotReadyException e) {
throw new NotReadyException(e);
} catch (final RobustEstimatorException | IOException e) {
throw new CalibrationException(e);
} finally {
running = false;
}
}
/**
* Returns method being used for robust estimation.
*
* @return method being used for robust estimation.
*/
@Override
public RobustEstimatorMethod getMethod() {
return RobustEstimatorMethod.PROMEDS;
}
/**
* Indicates whether this calibrator requires quality scores for each
* measurement or not.
*
* @return true if quality scores are required, false otherwise.
*/
@Override
public boolean isQualityScoresRequired() {
return true;
}
/**
* Sets quality scores corresponding to each provided sample.
* This method is used internally and does not check whether instance is
* locked or not.
*
* @param qualityScores quality scores to be set.
* @throws IllegalArgumentException if provided quality scores length
* is smaller than 3 samples.
*/
private void internalSetQualityScores(final double[] qualityScores) {
if (qualityScores == null || qualityScores.length < MINIMUM_MEASUREMENTS) {
throw new IllegalArgumentException();
}
this.qualityScores = qualityScores;
}
}