1   /* Copyright 2002-2023 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.time;
18  
19  import org.hipparchus.CalculusFieldElement;
20  
21  /** GPS time scale.
22   * <p>By convention, TGPS = TAI - 19 s.</p>
23   * <p>This is intended to be accessed thanks to {@link TimeScales},
24   * so there is no public constructor.</p>
25   * @author Luc Maisonobe
26   * @see AbsoluteDate
27   */
28  public class GPSScale implements TimeScale {
29  
30      /** Serializable UID. */
31      private static final long serialVersionUID = 20131209L;
32  
33      /** Offset from TAI. */
34      private static final double OFFSET = -19;
35  
36      /** Package private constructor for the factory.
37       */
38      GPSScale() {
39      }
40  
41      /** {@inheritDoc} */
42      @Override
43      public double offsetFromTAI(final AbsoluteDate date) {
44          return OFFSET;
45      }
46  
47      /** {@inheritDoc} */
48      @Override
49      public <T extends CalculusFieldElement<T>> T offsetFromTAI(final FieldAbsoluteDate<T> date) {
50          return date.getField().getZero().add(OFFSET);
51      }
52  
53      /** {@inheritDoc} */
54      @Override
55      public double offsetToTAI(final DateComponents date, final TimeComponents time) {
56          return -OFFSET;
57      }
58  
59      /** {@inheritDoc} */
60      public String getName() {
61          return "GPS";
62      }
63  
64      /** {@inheritDoc} */
65      public String toString() {
66          return getName();
67      }
68  
69  }