SubFrame2.java

  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.gnss.rflink.gps;

  19. import org.hipparchus.util.FastMath;
  20. import org.orekit.gnss.metric.parser.Units;

  22. /**
  23.  * Container for sub-frames 2.
  24.  * <p>
  25.  * Table 20-1, sheet 2 and table 40-1, sheet 2 in
  26.  * <a href="https://navcen.uscg.gov/sites/default/files/pdf/gps/IS-GPS-200N.pdf">NAVSTAR
  27.  * GPS Space Segment/Navigation User Segment Interface</a>, IS-GPS-200N, 22 Aug 2022
  28.  * </p>
  29.  * @author Luc Maisonobe
  30.  * @since 12.0
  31.  */
  32. public class SubFrame2 extends SubFrame {

  34.     /** Index of IODE field. */
  35.     private static final int IODE = 7;

  37.     /** Index of Crs field. */
  38.     private static final int CRS = 8;

  40.     /** Index of Δn field. */
  41.     private static final int DELTA_N = 9;

  43.     /** Index of MO field. */
  44.     private static final int M0 = 10;

  46.     /** Index of Cuc field. */
  47.     private static final int CUC = 11;

  49.     /** Index of e field. */
  50.     private static final int E = 12;

  52.     /** Index of Cus field. */
  53.     private static final int CUS = 13;

  55.     /** Index of √a field. */
  56.     private static final int SQRT_A = 14;

  58.     /** Index of TOE field. */
  59.     private static final int TOE = 15;

  61.     /** Index of it interval field. */
  62.     private static final int FIT_INTERVAL = 16;

  64.     /** Index of AODO field. */
  65.     private static final int AODO = 17;

  67.     /** Simple constructor.
  68.      * @param words raw words
  69.      */
  70.     SubFrame2(final int[] words) {

  72.         // create raw container
  73.         super(words, AODO + 1);

  75.         // populate container
  76.         setField(IODE,          3, 22,  8, words);
  77.         setField(CRS,           3,  6, 16, words);
  78.         setField(DELTA_N,       4, 14, 16, words);
  79.         setField(M0,            4,  6,  8, 5,  6, 24, words);
  80.         setField(CUC,           6, 14, 16, words);
  81.         setField(E,             6,  6,  8, 7,  6, 24, words);
  82.         setField(CUS,           8, 14, 16, words);
  83.         setField(SQRT_A,        8,  6,  8, 9,  6, 24, words);
  84.         setField(TOE,          10, 14, 16, words);
  85.         setField(FIT_INTERVAL, 10, 13,  1, words);
  86.         setField(AODO,         10,  8,  5, words);

  88.     }

  90.     /** Get Issue Of Data (ephemeris).
  91.      * @return Issue Of Data (ephemeris)
  92.      */
  93.     public int getIODE() {
  94.         return getField(IODE);
  95.     }

  97.     /** Get Crs.
  98.      * @return crs (m)
  99.      */
  100.     public double getCrs() {
  101.         return FastMath.scalb((double) getField(CRS), -5);
  102.     }

  104.     /** Get Δn.
  105.      * @return Δn (rad/s)
  106.      */
  107.     public double getDeltaN() {
  108.         return Units.SEMI_CIRCLE.toSI(FastMath.scalb((double) getField(DELTA_N), -43));
  109.     }

  111.     /** Get M₀.
  112.      * @return M₀ (rad)
  113.      */
  114.     public double getM0() {
  115.         return Units.SEMI_CIRCLE.toSI(FastMath.scalb((double) getField(M0), -31));
  116.     }

  118.     /** Get Cuc.
  119.      * @return Cuc (rad)
  120.      */
  121.     public double getCuc() {
  122.         return Units.SEMI_CIRCLE.toSI(FastMath.scalb((double) getField(CUC), -29));
  123.     }

  125.     /** Get e.
  126.      * @return e
  127.      */
  128.     public double getE() {
  129.         return FastMath.scalb((double) getField(E), -33);
  130.     }

  132.     /** Get Cus.
  133.      * @return Cus (rad)
  134.      */
  135.     public double getCus() {
  136.         return Units.SEMI_CIRCLE.toSI(FastMath.scalb((double) getField(CUS), -29));
  137.     }

  139.     /** Get √a.
  140.      * @return d√a (√m)
  141.      */
  142.     public double getSqrtA() {
  143.         return FastMath.scalb((double) getField(SQRT_A), -19);
  144.     }

  146.     /** Get Time Of Ephemeris.
  147.      * @return Time Of Ephemeris
  148.      */
  149.     public int getToe() {
  150.         return getField(TOE) << 4;
  151.     }

  153.     /** Get fit interval.
  154.      * @return fit interval
  155.      */
  156.     public int getFitInterval() {
  157.         return getField(FIT_INTERVAL);
  158.     }

  160.     /** Get Age Of data Offset.
  161.      * @return Age Of Data Offset (s)
  162.      */
  163.     public int getAODO() {
  164.         return getField(AODO) * 900;
  165.     }

  167. }
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