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.models.earth.tessellation;
18  
19  import java.util.Arrays;
20  import java.util.List;
21  
22  import org.hipparchus.geometry.euclidean.threed.Vector3D;
23  import org.hipparchus.util.FastMath;
24  import org.hipparchus.util.SinCos;
25  import org.orekit.bodies.GeodeticPoint;
26  import org.orekit.bodies.OneAxisEllipsoid;
27  
28  /** Class used to orient tiles with respect to a geographic azimuth.
29   * @see AlongTrackAiming
30   * @see DivertedSingularityAiming
31   * @author Luc Maisonobe
32   */
33  public class ConstantAzimuthAiming implements TileAiming {
34  
35      /** Sine and Cosine of the azimuth. */
36      private final SinCos sc;
37  
38      /** Simple constructor.
39       * @param ellipsoid ellipsoid body on which the zone is defined
40       * @param azimuth geographic azimuth of the tiles
41       */
42      public ConstantAzimuthAiming(final OneAxisEllipsoid ellipsoid, final double azimuth) {
43          this.sc = FastMath.sinCos(azimuth);
44      }
45  
46      /** {@inheritDoc} */
47      @Override
48      public List<GeodeticPoint> getSingularPoints() {
49          return Arrays.asList(GeodeticPoint.NORTH_POLE, GeodeticPoint.SOUTH_POLE);
50      }
51  
52      /** {@inheritDoc} */
53      @Override
54      public Vector3D alongTileDirection(final Vector3D point, final GeodeticPoint gp) {
55  
56          // compute the horizontal direction at fixed azimuth
57          return new Vector3D(sc.cos(), gp.getNorth(), sc.sin(), gp.getEast());
58  
59      }
60  
61  }