PhysicalEstimatedState.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.estimation.sequential;

import org.hipparchus.linear.RealMatrix;
import org.hipparchus.linear.RealVector;
import org.orekit.errors.OrekitIllegalArgumentException;
import org.orekit.errors.OrekitMessages;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.TimeStamped;

/** Container for smoothed states (time, mean and covariance) generated by an {@link RtsSmoother}.
 *
 * <p>The order of the parameters in the state and covariance are the same as produced by the underlying sequential
 * (Kalman or unscented) estimator.</p>
 * @see RtsSmoother
 * @author Mark Rutten
 * @since 13.0
 */
public class PhysicalEstimatedState implements TimeStamped {

    /** Date. */
    private final AbsoluteDate date;

    /** State mean. */
    private final RealVector state;

    /** State covariance. */
    private final RealMatrix covarianceMatrix;

    public PhysicalEstimatedState(final AbsoluteDate date,
                                  final RealVector state,
                                  final RealMatrix covarianceMatrix) {
        this.date = date;
        this.state = state;
        this.covarianceMatrix = covarianceMatrix;

        final int dim = state.getDimension();
        if (!covarianceMatrix.isSquare()) {
            throw new OrekitIllegalArgumentException(OrekitMessages.COVARIANCE_MUST_BE_SQUARE);
        }
        if (covarianceMatrix.getRowDimension() != dim) {
            throw new OrekitIllegalArgumentException(OrekitMessages.INCONSISTENT_STATE_DIMENSIONS,
                    dim, covarianceMatrix.getRowDimension());
        }
    }

    /** {@inheritDoc} */
    @Override
    public AbsoluteDate getDate() {
        return date;
    }

    /** Get the state in "physical" (not normalised) units.
     * @return the state mean
     */
    public RealVector getState() {
        return state;
    }

    /** Get the covariance matrix in "physical" (not normalised) units.
     * @return the state covariance matrix
     */
    public RealMatrix getCovarianceMatrix() {
        return covarianceMatrix;
    }
}