SingleLayerModelMappingFunction.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.ionosphere;
- import org.hipparchus.CalculusFieldElement;
- import org.hipparchus.util.FastMath;
- /**
- * Single Layer Model (SLM) ionospheric mapping function.
- * <p>
- * The SLM mapping function assumes a single ionospheric layer with a constant height
- * for the computation of the mapping factor.
- * </p>
- * @see "N. Ya’acob, M. Abdullah and M. Ismail, Determination of the GPS
- * total electron content using single layer model (SLM) ionospheric
- * mapping function, in International Journal of Computer Science and
- * Network Security, vol. 8, no. 9, pp. 154-160, 2008."
- *
- * @author Bryan Cazabonne
- * @since 10.2
- */
- public class SingleLayerModelMappingFunction implements IonosphericMappingFunction {
- /** Default value for the height of the ionospheric single layer in meters. */
- private static final double DEFAULT_HEIGHT = 450e3;
- /** Mean Earth radius in meters. */
- private static final double RE = 6371e3;
- /** Height of the ionospheric single layer in meters.*/
- private final double hIon;
- /**
- * Constructor with default value.
- * <p>
- * Using this constructor, the height of the ionospheric single
- * layer is equal to 450 kilometers as recommended by the IERS
- * Convention 2010.
- * </p>
- */
- public SingleLayerModelMappingFunction() {
- this(DEFAULT_HEIGHT);
- }
- /**
- * Constructor.
- * @param hIon height of the ionospheric single layer in meters
- */
- public SingleLayerModelMappingFunction(final double hIon) {
- this.hIon = hIon;
- }
- /** {@inheritDoc} */
- @Override
- public double mappingFactor(final double elevation) {
- // Calculate the zenith angle from the elevation
- final double z = FastMath.abs(0.5 * FastMath.PI - elevation);
- // Distance ratio
- final double ratio = RE / (RE + hIon);
- // Mapping function
- final double coef = FastMath.sin(z) * ratio;
- return 1.0 / FastMath.sqrt(1.0 - coef * coef);
- }
- /** {@inheritDoc} */
- @Override
- public <T extends CalculusFieldElement<T>> T mappingFactor(final T elevation) {
- // Calculate the zenith angle from the elevation
- final T z = FastMath.abs(elevation.negate().add(elevation.getPi().multiply(0.5)));
- // Distance ratio
- final double ratio = RE / (RE + hIon);
- // Mapping function
- final T coef = FastMath.sin(z).multiply(ratio);
- return FastMath.sqrt(coef.multiply(coef).negate().add(1.0)).reciprocal();
- }
- }