1   /* Copyright 2022-2025 Thales Alenia Space
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.models.earth.weather;
18  
19  import org.hipparchus.CalculusFieldElement;
20  import org.hipparchus.util.SinCos;
21  import org.hipparchus.util.FieldSinCos;
22  
23  /** Seasonal model used in Global Pressure Temperature models.
24   * @see "Landskron, D. & Böhm, J. J Geod (2018)
25   *      VMF3/GPT3: refined discrete and empirical troposphere mapping functions
26   *      92: 349. https://doi.org/10.1007/s00190-017-1066-2"
27   * @author Luc Maisonobe
28   * @since 12.1
29   */
30  class SeasonalModel {
31  
32      /** Constant. */
33      private final double a0;
34  
35      /** Annual cosine amplitude. */
36      private final double a1;
37  
38      /** Annual sine amplitude. */
39      private final double b1;
40  
41      /** Semi-annual cosine amplitude. */
42      private final double a2;
43  
44      /** Semi-annual sine amplitude. */
45      private final double b2;
46  
47      /** Simple constructor.
48       * @param a0 constant
49       * @param a1 annual cosine amplitude
50       * @param b1 annual sine amplitude
51       * @param a2 semi-annual cosine amplitude
52       * @param b2 semi-annual sine amplitude
53       */
54      SeasonalModel(final double a0, final double a1, final double b1, final double a2, final double b2) {
55          this.a0 = a0;
56          this.a1 = a1;
57          this.b1 = b1;
58          this.a2 = a2;
59          this.b2 = b2;
60      }
61  
62      /** Evaluate a model for some day.
63       * @param sc1 sine and cosine of yearly harmonic term
64       * @param sc2 sine and cosine of bi-yearly harmonic term
65       * @return model value at specified day
66       * @since 13.0
67       */
68      public double evaluate(final SinCos sc1, final SinCos sc2) {
69          return a0 + a1 * sc1.cos() + b1 * sc1.sin() + a2 * sc2.cos() + b2 * sc2.sin();
70      }
71  
72      /** Evaluate a model for some day.
73       * @param <T> type of the field elements
74       * @param sc1 sine and cosine of yearly harmonic term
75       * @param sc2 sine and cosine of bi-yearly harmonic term
76       * @return model value at specified day
77       * @since 13.0
78       */
79      public <T extends CalculusFieldElement<T>> T evaluate(final FieldSinCos<T> sc1, final FieldSinCos<T> sc2) {
80          return sc1.cos().multiply(a1).
81              add(sc1.sin().multiply(b1)).
82              add(sc2.cos().multiply(a2)).
83              add(sc2.sin().multiply(b2)).
84              add(a0);
85      }
86  
87  }