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.gnss.metric.messages.common;
18  
19  /** Signal-In-Space Accuracy (SISA).
20   * @see "Galileo OS Signal-In-Space Interface Control Document, Issue 1.3, December 2016, Table 76"
21   * @author Bryan Cazabonne
22   * @since 11.0
23   */
24  public class SignalInSpaceAccuracy implements AccuracyProvider {
25  
26      /** Signal In Space Accuracy indicator. */
27      private final int sisaIndex;
28  
29      /**
30       * Simple constructor.
31       * @param index integer value of the signal in space accuracy
32       */
33      public SignalInSpaceAccuracy(final int index) {
34          this.sisaIndex = index;
35      }
36  
37      /** {@inheritDoc} */
38      @Override
39      public double getAccuracy() {
40          // Cast index to a double value
41          final double id = (double) sisaIndex;
42          // Compute accuracy
43          if (sisaIndex < 50) {
44              // Accuracy is between 0 cm and 49 cm with 1 cm resolution
45              return 0.01 * id;
46          } else if (sisaIndex < 75) {
47              // Accuracy is between 50 cm and 98 cm with 2 cm resolution
48              return 0.01 * (50.0 + 2.0 * (id - 50.0));
49          } else if (sisaIndex < 100) {
50              // Accuracy is between 1 m and 2 m with 4 cm resolution
51              return 1.0 + 0.04 * (id - 75.0);
52          } else if (sisaIndex < 126) {
53              // Accuracy is between 2 m and 6 m with 16 cm resolution
54              return 2.0 + 0.16 * (id - 100.0);
55          } else {
56              // Spare or No Accuracy Predicition Available (NAPA)
57              return -1.0;
58          }
59      }
60  
61  }