1 /* Copyright 2002-2025 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.util.MathArrays;
20 import org.orekit.gnss.GnssSignal;
21 import org.orekit.gnss.MeasurementType;
22 import org.orekit.gnss.SatelliteSystem;
23
24 /**
25 * Narrow-Lane combination.
26 * <p>
27 * This combination create signal with a narrow wavelength.
28 * The signal in this combination has a lower noise than each
29 * separated separeted component.
30 * </p>
31 * <pre>
32 * f1 * m1 + f2 * m2
33 * mNL = -----------------------
34 * f1 + f2
35 * </pre>
36 * With:
37 * <ul>
38 * <li>mNL : Narrow-laning measurement.</li>
39 * <li>f1 : Frequency of the first measurement.</li>
40 * <li>pr1 : First measurement.</li>
41 * <li>f2 : Frequency of the second measurement.</li>
42 * <li>m1 : Second measurement.</li>
43 * </ul>
44 * <p>
45 * Narrow-Lane combination is a dual frequency combination.
46 * The two measurements shall have different frequencies but they must have the same {@link MeasurementType}.
47 * </p>
48 * @author Bryan Cazabonne
49 * @since 10.1
50 */
51 public class NarrowLaneCombination extends AbstractDualFrequencyCombination {
52
53 /**
54 * Package private constructor for the factory.
55 * @param system satellite system for which the combination is applied
56 */
57 NarrowLaneCombination(final SatelliteSystem system) {
58 super(CombinationType.NARROW_LANE, system);
59 }
60
61 /** {@inheritDoc} */
62 @Override
63 protected double getCombinedValue(final double obs1, final GnssSignal s1,
64 final double obs2, final GnssSignal s2) {
65 // Get the ration f/f0
66 final double ratioF1 = s1.getRatio();
67 final double ratioF2 = s2.getRatio();
68 // Perform combination
69 return MathArrays.linearCombination(ratioF1, obs1, ratioF2, obs2) / (ratioF1 + ratioF2);
70 }
71
72 /** {@inheritDoc} */
73 @Override
74 protected double getCombinedFrequency(final GnssSignal s1, final GnssSignal s2) {
75 return s1.getFrequency() + s2.getFrequency();
76 }
77
78 }