AbsolutePVCoordinates.java
/* Copyright 2002-2019 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.utils;
import java.io.Serializable;
import java.util.stream.Stream;
import org.hipparchus.analysis.differentiation.DerivativeStructure;
import org.hipparchus.analysis.interpolation.HermiteInterpolator;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.util.FastMath;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitIllegalArgumentException;
import org.orekit.errors.OrekitInternalError;
import org.orekit.errors.OrekitMessages;
import org.orekit.frames.Frame;
import org.orekit.frames.Transform;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.TimeInterpolable;
import org.orekit.time.TimeStamped;
/** Position - Velocity - Acceleration linked to a date and a frame.
*/
public class AbsolutePVCoordinates extends TimeStampedPVCoordinates
implements TimeStamped, TimeInterpolable<AbsolutePVCoordinates>,
Serializable, PVCoordinatesProvider {
/** Serializable UID. */
private static final long serialVersionUID = 20150824L;
/** Frame in which are defined the coordinates. */
private final Frame frame;
/** Build from position, velocity, acceleration.
* @param frame the frame in which the coordinates are defined
* @param date coordinates date
* @param position the position vector (m)
* @param velocity the velocity vector (m/s)
* @param acceleration the acceleration vector (m/sÂý)
*/
public AbsolutePVCoordinates(final Frame frame, final AbsoluteDate date,
final Vector3D position, final Vector3D velocity, final Vector3D acceleration) {
super(date, position, velocity, acceleration);
this.frame = frame;
}
/** Build from position and velocity. Acceleration is set to zero.
* @param frame the frame in which the coordinates are defined
* @param date coordinates date
* @param position the position vector (m)
* @param velocity the velocity vector (m/s)
*/
public AbsolutePVCoordinates(final Frame frame, final AbsoluteDate date,
final Vector3D position,
final Vector3D velocity) {
this(frame, date, position, velocity, Vector3D.ZERO);
}
/** Build from frame, date and PVA coordinates.
* @param frame the frame in which the coordinates are defined
* @param date date of the coordinates
* @param pva TimeStampedPVCoordinates
*/
public AbsolutePVCoordinates(final Frame frame, final AbsoluteDate date, final PVCoordinates pva) {
super(date, pva);
this.frame = frame;
}
/** Build from frame and TimeStampedPVCoordinates.
* @param frame the frame in which the coordinates are defined
* @param pva TimeStampedPVCoordinates
*/
public AbsolutePVCoordinates(final Frame frame, final TimeStampedPVCoordinates pva) {
super(pva.getDate(), pva);
this.frame = frame;
}
/** Multiplicative constructor
* <p>Build a AbsolutePVCoordinates from another one and a scale factor.</p>
* <p>The TimeStampedPVCoordinates built will be a * AbsPva</p>
* @param date date of the built coordinates
* @param a scale factor
* @param AbsPva base (unscaled) AbsolutePVCoordinates
*/
public AbsolutePVCoordinates(final AbsoluteDate date,
final double a, final AbsolutePVCoordinates AbsPva) {
super(date, a, AbsPva);
this.frame = AbsPva.frame;
}
/** Subtractive constructor
* <p>Build a relative AbsolutePVCoordinates from a start and an end position.</p>
* <p>The AbsolutePVCoordinates built will be end - start.</p>
* <p>In case start and end use two different pseudo-inertial frames,
* the new AbsolutePVCoordinates arbitrarily be defined in the start frame. </p>
* @param date date of the built coordinates
* @param start Starting AbsolutePVCoordinates
* @param end ending AbsolutePVCoordinates
*/
public AbsolutePVCoordinates(final AbsoluteDate date,
final AbsolutePVCoordinates start, final AbsolutePVCoordinates end) {
super(date, start, end);
ensureIdenticalFrames(start, end);
this.frame = start.frame;
}
/** Linear constructor
* <p>Build a AbsolutePVCoordinates from two other ones and corresponding scale factors.</p>
* <p>The AbsolutePVCoordinates built will be a1 * u1 + a2 * u2</p>
* <p>In case the AbsolutePVCoordinates use different pseudo-inertial frames,
* the new AbsolutePVCoordinates arbitrarily be defined in the first frame. </p>
* @param date date of the built coordinates
* @param a1 first scale factor
* @param absPv1 first base (unscaled) AbsolutePVCoordinates
* @param a2 second scale factor
* @param absPv2 second base (unscaled) AbsolutePVCoordinates
*/
public AbsolutePVCoordinates(final AbsoluteDate date,
final double a1, final AbsolutePVCoordinates absPv1,
final double a2, final AbsolutePVCoordinates absPv2) {
super(date, a1, absPv1.getPVCoordinates(), a2, absPv2.getPVCoordinates());
ensureIdenticalFrames(absPv1, absPv2);
this.frame = absPv1.getFrame();
}
/** Linear constructor
* <p>Build a AbsolutePVCoordinates from three other ones and corresponding scale factors.</p>
* <p>The AbsolutePVCoordinates built will be a1 * u1 + a2 * u2 + a3 * u3</p>
* <p>In case the AbsolutePVCoordinates use different pseudo-inertial frames,
* the new AbsolutePVCoordinates arbitrarily be defined in the first frame. </p>
* @param date date of the built coordinates
* @param a1 first scale factor
* @param absPv1 first base (unscaled) AbsolutePVCoordinates
* @param a2 second scale factor
* @param absPv2 second base (unscaled) AbsolutePVCoordinates
* @param a3 third scale factor
* @param absPv3 third base (unscaled) AbsolutePVCoordinates
*/
public AbsolutePVCoordinates(final AbsoluteDate date,
final double a1, final AbsolutePVCoordinates absPv1,
final double a2, final AbsolutePVCoordinates absPv2,
final double a3, final AbsolutePVCoordinates absPv3) {
super(date, a1, absPv1.getPVCoordinates(), a2, absPv2.getPVCoordinates(),
a3, absPv3.getPVCoordinates());
ensureIdenticalFrames(absPv1, absPv2);
ensureIdenticalFrames(absPv1, absPv3);
this.frame = absPv1.getFrame();
}
/** Linear constructor
* <p>Build a AbsolutePVCoordinates from four other ones and corresponding scale factors.</p>
* <p>The AbsolutePVCoordinates built will be a1 * u1 + a2 * u2 + a3 * u3 + a4 * u4</p>
* <p>In case the AbsolutePVCoordinates use different pseudo-inertial frames,
* the new AbsolutePVCoordinates arbitrarily be defined in the first frame. </p>
* @param date date of the built coordinates
* @param a1 first scale factor
* @param absPv1 first base (unscaled) AbsolutePVCoordinates
* @param a2 second scale factor
* @param absPv2 second base (unscaled) AbsolutePVCoordinates
* @param a3 third scale factor
* @param absPv3 third base (unscaled) AbsolutePVCoordinates
* @param a4 fourth scale factor
* @param absPv4 fourth base (unscaled) AbsolutePVCoordinates
*/
public AbsolutePVCoordinates(final AbsoluteDate date,
final double a1, final AbsolutePVCoordinates absPv1,
final double a2, final AbsolutePVCoordinates absPv2,
final double a3, final AbsolutePVCoordinates absPv3,
final double a4, final AbsolutePVCoordinates absPv4) {
super(date, a1, absPv1.getPVCoordinates(), a2, absPv2.getPVCoordinates(),
a3, absPv3.getPVCoordinates(), a4, absPv4.getPVCoordinates());
ensureIdenticalFrames(absPv1, absPv2);
ensureIdenticalFrames(absPv1, absPv3);
ensureIdenticalFrames(absPv1, absPv4);
this.frame = absPv1.getFrame();
}
/** Builds a AbsolutePVCoordinates triplet from a {@link FieldVector3D}<{@link DerivativeStructure}>.
* <p>
* The vector components must have time as their only derivation parameter and
* have consistent derivation orders.
* </p>
* @param frame the frame in which the parameters are defined
* @param date date of the built coordinates
* @param p vector with time-derivatives embedded within the coordinates
*/
public AbsolutePVCoordinates(final Frame frame, final AbsoluteDate date,
final FieldVector3D<DerivativeStructure> p) {
super(date, p);
this.frame = frame;
}
/** Ensure that the frames from two AbsolutePVCoordinates are identical.
* @param absPv1 first AbsolutePVCoordinates
* @param absPv2 first AbsolutePVCoordinates
* @throws OrekitIllegalArgumentException if frames are different
*/
private static void ensureIdenticalFrames(final AbsolutePVCoordinates absPv1, final AbsolutePVCoordinates absPv2)
throws OrekitIllegalArgumentException {
if (!absPv1.frame.equals(absPv2.frame)) {
throw new OrekitIllegalArgumentException(OrekitMessages.INCOMPATIBLE_FRAMES,
absPv1.frame.getName(), absPv2.frame.getName());
}
}
/** Get a time-shifted state.
* <p>
* The state can be slightly shifted to close dates. This shift is based on
* a simple Taylor expansion. It is <em>not</em> intended as a replacement for
* proper orbit propagation (it is not even Keplerian!) but should be sufficient
* for either small time shifts or coarse accuracy.
* </p>
* @param dt time shift in seconds
* @return a new state, shifted with respect to the instance (which is immutable)
*/
public AbsolutePVCoordinates shiftedBy(final double dt) {
final TimeStampedPVCoordinates spv = super.shiftedBy(dt);
return new AbsolutePVCoordinates(frame, spv);
}
/** Create a local provider using simply Taylor expansion through {@link #shiftedBy(double)}.
* <p>
* The time evolution is based on a simple Taylor expansion. It is <em>not</em> intended as a
* replacement for proper orbit propagation (it is not even Keplerian!) but should be sufficient
* for either small time shifts or coarse accuracy.
* </p>
* @return provider based on Taylor expansion, for small time shifts around instance date
*/
public PVCoordinatesProvider toTaylorProvider() {
return new PVCoordinatesProvider() {
/** {@inheritDoc} */
public TimeStampedPVCoordinates getPVCoordinates(final AbsoluteDate d, final Frame f) {
final TimeStampedPVCoordinates shifted = shiftedBy(d.durationFrom(getDate()));
final Transform transform = frame.getTransformTo(f, d);
return transform.transformPVCoordinates(shifted);
}
};
}
/** Get the frame in which the coordinates are defined.
* @return frame in which the coordinates are defined
*/
public Frame getFrame() {
return frame;
}
/** Get the TimeStampedPVCoordinates.
* @return TimeStampedPVCoordinates
*/
public TimeStampedPVCoordinates getPVCoordinates() {
return this;
}
/** Get the TimeStampedPVCoordinates in a specified frame.
* @param outputFrame frame in which the position/velocity coordinates shall be computed
* @return TimeStampedPVCoordinates
* @exception OrekitException if transformation between frames cannot be computed
* @see #getPVCoordinates()
*/
public TimeStampedPVCoordinates getPVCoordinates(final Frame outputFrame) {
// If output frame requested is the same as definition frame,
// PV coordinates are returned directly
if (outputFrame == frame) {
return getPVCoordinates();
}
// Else, PV coordinates are transformed to output frame
final Transform t = frame.getTransformTo(outputFrame, getDate());
return t.transformPVCoordinates(getPVCoordinates());
}
@Override
public TimeStampedPVCoordinates getPVCoordinates(final AbsoluteDate otherDate, final Frame outputFrame) {
return shiftedBy(otherDate.durationFrom(getDate())).getPVCoordinates(outputFrame);
}
@Override
public AbsolutePVCoordinates interpolate(final AbsoluteDate date, final Stream<AbsolutePVCoordinates> sample) {
return interpolate(getFrame(), date, CartesianDerivativesFilter.USE_PVA, sample);
}
/** Interpolate position-velocity.
* <p>
* The interpolated instance is created by polynomial Hermite interpolation
* ensuring velocity remains the exact derivative of position.
* </p>
* <p>
* Note that even if first time derivatives (velocities)
* from sample can be ignored, the interpolated instance always includes
* interpolated derivatives. This feature can be used explicitly to
* compute these derivatives when it would be too complex to compute them
* from an analytical formula: just compute a few sample points from the
* explicit formula and set the derivatives to zero in these sample points,
* then use interpolation to add derivatives consistent with the positions.
* </p>
* @param frame frame for the interpolted instance
* @param date interpolation date
* @param filter filter for derivatives from the sample to use in interpolation
* @param sample sample points on which interpolation should be done
* @return a new position-velocity, interpolated at specified date
* @exception OrekitIllegalArgumentException if some elements in the sample do not
* have the same defining frame as other
*/
public static AbsolutePVCoordinates interpolate(final Frame frame, final AbsoluteDate date,
final CartesianDerivativesFilter filter,
final Stream<AbsolutePVCoordinates> sample) {
// set up an interpolator taking derivatives into account
final HermiteInterpolator interpolator = new HermiteInterpolator();
// add sample points
switch (filter) {
case USE_P :
// populate sample with position data, ignoring velocity
sample.forEach(pv -> {
final Vector3D position = pv.getPosition();
interpolator.addSamplePoint(pv.getDate().durationFrom(date),
position.toArray());
});
break;
case USE_PV :
// populate sample with position and velocity data
sample.forEach(pv -> {
final Vector3D position = pv.getPosition();
final Vector3D velocity = pv.getVelocity();
interpolator.addSamplePoint(pv.getDate().durationFrom(date),
position.toArray(), velocity.toArray());
});
break;
case USE_PVA :
// populate sample with position, velocity and acceleration data
sample.forEach(pv -> {
final Vector3D position = pv.getPosition();
final Vector3D velocity = pv.getVelocity();
final Vector3D acceleration = pv.getAcceleration();
interpolator.addSamplePoint(pv.getDate().durationFrom(date),
position.toArray(), velocity.toArray(), acceleration.toArray());
});
break;
default :
// this should never happen
throw new OrekitInternalError(null);
}
// interpolate
final double[][] p = interpolator.derivatives(0.0, 2);
// build a new interpolated instance
return new AbsolutePVCoordinates(frame, date, new Vector3D(p[0]), new Vector3D(p[1]), new Vector3D(p[2]));
}
/** Replace the instance with a data transfer object for serialization.
* @return data transfer object that will be serialized
*/
private Object writeReplace() {
return new DTO(this);
}
/** Internal class used only for serialization. */
private static class DTO implements Serializable {
/** Serializable UID. */
private static final long serialVersionUID = 20150916L;
/** Double values. */
private double[] d;
/** Frame in which acoordinates are defined. */
private final Frame frame;
/** Simple constructor.
* @param absPva instance to serialize
*/
private DTO(final AbsolutePVCoordinates absPva) {
// decompose date
final double epoch = FastMath.floor(absPva.getDate().durationFrom(AbsoluteDate.J2000_EPOCH));
final double offset = absPva.getDate().durationFrom(AbsoluteDate.J2000_EPOCH.shiftedBy(epoch));
this.d = new double[] {
epoch, offset,
absPva.getPosition().getX(), absPva.getPosition().getY(), absPva.getPosition().getZ(),
absPva.getVelocity().getX(), absPva.getVelocity().getY(), absPva.getVelocity().getZ(),
absPva.getAcceleration().getX(), absPva.getAcceleration().getY(), absPva.getAcceleration().getZ()
};
this.frame = absPva.frame;
}
/** Replace the deserialized data transfer object with a {@link AbsolutePVCoordinates}.
* @return replacement {@link AbsolutePVCoordinates}
*/
private Object readResolve() {
return new AbsolutePVCoordinates(frame,
AbsoluteDate.J2000_EPOCH.shiftedBy(d[0]).shiftedBy(d[1]),
new Vector3D(d[2], d[3], d[ 4]),
new Vector3D(d[5], d[6], d[ 7]),
new Vector3D(d[8], d[9], d[10]));
}
}
}