1 /* Copyright 2002-2026 CS GROUP
2 * Licensed to CS GROUP (CS) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * CS licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.orekit.estimation.measurements.gnss;
18
19 import org.hipparchus.analysis.differentiation.Gradient;
20 import org.orekit.estimation.measurements.EstimatedMeasurement;
21 import org.orekit.estimation.measurements.EstimatedMeasurementBase;
22 import org.orekit.estimation.measurements.MeasurementQuality;
23 import org.orekit.estimation.measurements.ObservableSatellite;
24 import org.orekit.estimation.measurements.Observer;
25 import org.orekit.propagation.SpacecraftState;
26 import org.orekit.signal.SignalTravelTimeModel;
27 import org.orekit.time.AbsoluteDate;
28 import org.orekit.utils.Constants;
29 import org.orekit.utils.TimeStampedPVCoordinates;
30
31 /** One-way GNSS phase measurement.
32 * <p>
33 * This class can be used in precise orbit determination applications
34 * for modeling a phase measurement between a GNSS emitter
35 * and a LEO satellite (receiver).
36 * <p>
37 * The one-way GNSS phase measurement assumes knowledge of the orbit and
38 * the clock offset of the emitting GNSS satellite. For instance, it is
39 * possible to use a SP3 file or a GNSS navigation message to recover
40 * the satellite's orbit and clock.
41 * <p>
42 * This class is very similar to {@link InterSatellitesPhase} measurement
43 * class. However, using the one-way GNSS phase measurement, the orbit and clock
44 * of the emitting GNSS satellite are <b>NOT</b> estimated simultaneously with
45 * LEO satellite coordinates.
46 *
47 * @author Bryan Cazabonne
48 * @since 10.3
49 */
50 public class OneWayGNSSPhase extends AbstractOneWayGNSS<OneWayGNSSPhase> {
51
52 /** Type of the measurement. */
53 public static final String MEASUREMENT_TYPE = "OneWayGNSSPhase";
54
55 /** Driver for ambiguity. */
56 private final AmbiguityDriver ambiguityDriver;
57
58 /** Wavelength of the phase observed value [m]. */
59 private final double wavelength;
60
61 /** Simple constructor.
62 * @param observer object that sends signal
63 * @param date date of the measurement
64 * @param phase observed value, in cycles
65 * @param wavelength phase observed value wavelength, in meters
66 * @param sigma theoretical standard deviation
67 * @param baseWeight base weight
68 * @param local satellite which receives the signal and perform the measurement
69 * @param cache from which ambiguity drive should come
70 * @since 12.1
71 */
72 public OneWayGNSSPhase(final Observer observer,
73 final AbsoluteDate date,
74 final double phase, final double wavelength, final double sigma,
75 final double baseWeight, final ObservableSatellite local,
76 final AmbiguityCache cache) {
77 this(observer, date, phase, wavelength, new MeasurementQuality(sigma, baseWeight), new SignalTravelTimeModel(),
78 local, cache);
79 }
80
81 /** Simple constructor.
82 * @param observer object that sends signal
83 * @param date date of the measurement
84 * @param phase observed value, in cycles
85 * @param wavelength phase observed value wavelength, in meters
86 * @param measurementQuality measurement quality data as used in orbit determination
87 * @param signalTravelTimeModel signal model
88 * @param local satellite which receives the signal and perform the measurement
89 * @param cache from which ambiguity drive should come
90 * @since 14.0
91 */
92 public OneWayGNSSPhase(final Observer observer, final AbsoluteDate date,
93 final double phase, final double wavelength, final MeasurementQuality measurementQuality,
94 final SignalTravelTimeModel signalTravelTimeModel, final ObservableSatellite local,
95 final AmbiguityCache cache) {
96 // Call super constructor
97 super(observer, date, phase, measurementQuality, signalTravelTimeModel, local);
98
99 // Initialize phase ambiguity driver
100 ambiguityDriver = cache.getAmbiguity(observer.getName(), local.getName(), wavelength);
101
102 // Add ambiguity parameter to measurement
103 addParameterDriver(ambiguityDriver);
104
105 // Initialise fields
106 this.wavelength = wavelength;
107 }
108
109 /** Get the wavelength.
110 * @return wavelength (m)
111 */
112 public double getWavelength() {
113 return wavelength;
114 }
115
116 /** Get the driver for phase ambiguity.
117 * @return the driver for phase ambiguity
118 */
119 public AmbiguityDriver getAmbiguityDriver() {
120 return ambiguityDriver;
121 }
122
123 /** {@inheritDoc} */
124 @Override
125 protected EstimatedMeasurementBase<OneWayGNSSPhase> theoreticalEvaluationWithoutDerivatives(final int iteration,
126 final int evaluation,
127 final SpacecraftState[] states) {
128
129 final CommonParametersWithoutDerivatives common =
130 computeLocalParametersWithout(states, getSatellites().getFirst(), getDate());
131
132 // prepare the evaluation
133 final EstimatedMeasurementBase<OneWayGNSSPhase> estimatedPhase =
134 new EstimatedMeasurementBase<>(this, iteration, evaluation,
135 new SpacecraftState[] {
136 common.getState()
137 }, new TimeStampedPVCoordinates[] {
138 common.getRemotePV(),
139 common.getTransitPV()
140 });
141
142 // Phase value
143 final double cOverLambda = Constants.SPEED_OF_LIGHT / wavelength;
144 final double ambiguity = ambiguityDriver.getValue(common.getState().getDate());
145 final double phase = (common.getTauD() + common.getLocalOffset().getBias() -
146 common.getRemoteOffset().getBias()) * cOverLambda + ambiguity;
147
148 // Set value of the estimated measurement
149 estimatedPhase.setEstimatedValue(phase);
150
151 // Return the estimated measurement
152 return estimatedPhase;
153
154 }
155
156 /** {@inheritDoc} */
157 @Override
158 protected EstimatedMeasurement<OneWayGNSSPhase> theoreticalEvaluation(final int iteration,
159 final int evaluation,
160 final SpacecraftState[] states) {
161
162 final CommonParametersWithDerivatives common =
163 computeLocalParametersWith(states, getSatellites().getFirst(), getDate());
164
165 // prepare the evaluation
166 final EstimatedMeasurement<OneWayGNSSPhase> estimatedPhase =
167 new EstimatedMeasurement<>(this, iteration, evaluation,
168 new SpacecraftState[] {
169 common.getState()
170 }, new TimeStampedPVCoordinates[] {
171 common.getRemotePV().toTimeStampedPVCoordinates(),
172 common.getTransitPV().toTimeStampedPVCoordinates()
173 });
174
175 // Phase value
176 final double cOverLambda = Constants.SPEED_OF_LIGHT / wavelength;
177 final Gradient ambiguity = ambiguityDriver.getValue(common.getTauD().getFreeParameters(), common.getIndices(),
178 common.getState().getDate());
179 final Gradient phase = common.getTauD().add(common.getLocalOffset().getBias()).
180 subtract(common.getRemoteOffset().getBias()).
181 multiply(cOverLambda).add(ambiguity);
182
183 // Return the estimated measurement
184 fillDerivatives(phase, common.getIndices(), estimatedPhase);
185 return estimatedPhase;
186
187 }
188
189 }