DivertedSingularityAiming.java
- /* Copyright 2002-2024 CS GROUP
- * Licensed to CS GROUP (CS) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * CS licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- package org.orekit.models.earth.tessellation;
- import java.util.Collections;
- import java.util.List;
- import org.hipparchus.geometry.euclidean.threed.Vector3D;
- import org.hipparchus.geometry.spherical.twod.S2Point;
- import org.hipparchus.geometry.spherical.twod.SphericalPolygonsSet;
- import org.hipparchus.util.FastMath;
- import org.orekit.bodies.GeodeticPoint;
- /** Class used to orient tiles such that there are no singularities within the zone of interest.
- * <p>
- * This class is mainly useful for {@link EllipsoidTessellator#sample(org.hipparchus.geometry.spherical.twod.SphericalPolygonsSet,
- * double, double) sampling} a zone on ground when the grid directions is not really important
- * and when the zone contains the pole, which is a singular point for both
- * {@link ConstantAzimuthAiming} and {@link AlongTrackAiming}.
- * </p>
- * @see AlongTrackAiming
- * @see ConstantAzimuthAiming
- * @author Luc Maisonobe
- */
- public class DivertedSingularityAiming implements TileAiming {
- /** Singularity location. */
- private final Vector3D singularity;
- /** Singularity location. */
- private final GeodeticPoint singularityGP;
- /** Dipole moment. */
- private final Vector3D moment;
- /** Simple constructor.
- * @param forbiddenZone zone out of which singularity should be diverted
- */
- public DivertedSingularityAiming(final SphericalPolygonsSet forbiddenZone) {
- final S2Point outside = forbiddenZone.getEnclosingCap().getCenter().negate();
- this.singularity = outside.getVector();
- this.singularityGP = new GeodeticPoint(0.5 * FastMath.PI - outside.getPhi(), outside.getTheta(), 0.0);
- this.moment = singularity.orthogonal();
- }
- /** {@inheritDoc} */
- @Override
- public List<GeodeticPoint> getSingularPoints() {
- return Collections.singletonList(singularityGP);
- }
- /** {@inheritDoc} */
- @Override
- public Vector3D alongTileDirection(final Vector3D point, final GeodeticPoint gp) {
- // compute the dipole field at point
- final Vector3D p = new S2Point(gp.getLongitude(), 0.5 * FastMath.PI - gp.getLatitude()).getVector();
- final Vector3D r = p.subtract(singularity).normalize();
- final Vector3D field = new Vector3D(3.0 * Vector3D.dotProduct(moment, r), r, -1.0, moment);
- // the aiming direction is the horizontal component of the field
- final Vector3D horizontal = new Vector3D(1, field, -Vector3D.dotProduct(field, p), p);
- return horizontal.normalize();
- }
- }