ViennaOneModel.java
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package org.orekit.models.earth.troposphere;
import java.util.Collections;
import java.util.List;
import org.hipparchus.Field;
import org.hipparchus.CalculusFieldElement;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.MathArrays;
import org.orekit.annotation.DefaultDataContext;
import org.orekit.bodies.FieldGeodeticPoint;
import org.orekit.bodies.GeodeticPoint;
import org.orekit.data.DataContext;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.DateTimeComponents;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.time.TimeScale;
import org.orekit.utils.ParameterDriver;
/** The Vienna1 tropospheric delay model for radio techniques.
* The Vienna model data are given with a time interval of 6 hours
* as well as on a global 2.5° * 2.0° grid.
*
* This version considered the height correction for the hydrostatic part
* developed by Niell, 1996.
*
* @see "Boehm, J., Werl, B., and Schuh, H., (2006),
* Troposhere mapping functions for GPS and very long baseline
* interferometry from European Centre for Medium-Range Weather
* Forecasts operational analysis data, J. Geophy. Res., Vol. 111,
* B02406, doi:10.1029/2005JB003629"
*
* @author Bryan Cazabonne
*/
public class ViennaOneModel implements DiscreteTroposphericModel, MappingFunction {
/** The a coefficient for the computation of the wet and hydrostatic mapping functions.*/
private final double[] coefficientsA;
/** Values of hydrostatic and wet delays as provided by the Vienna model. */
private final double[] zenithDelay;
/** UTC time scale. */
private final TimeScale utc;
/** Build a new instance.
*
* <p>This constructor uses the {@link DataContext#getDefault() default data context}.
*
* @param coefficientA The a coefficients for the computation of the wet and hydrostatic mapping functions.
* @param zenithDelay Values of hydrostatic and wet delays
* @see #ViennaOneModel(double[], double[], TimeScale)
*/
@DefaultDataContext
public ViennaOneModel(final double[] coefficientA, final double[] zenithDelay) {
this(coefficientA, zenithDelay,
DataContext.getDefault().getTimeScales().getUTC());
}
/**
* Build a new instance.
*
* @param coefficientA The a coefficients for the computation of the wet and
* hydrostatic mapping functions.
* @param zenithDelay Values of hydrostatic and wet delays
* @param utc UTC time scale.
* @since 10.1
*/
public ViennaOneModel(final double[] coefficientA,
final double[] zenithDelay,
final TimeScale utc) {
this.coefficientsA = coefficientA.clone();
this.zenithDelay = zenithDelay.clone();
this.utc = utc;
}
/** {@inheritDoc} */
@Override
public double pathDelay(final double elevation, final GeodeticPoint point,
final double[] parameters, final AbsoluteDate date) {
// zenith delay
final double[] delays = computeZenithDelay(point, parameters, date);
// mapping function
final double[] mappingFunction = mappingFactors(elevation, point, date);
// Tropospheric path delay
return delays[0] * mappingFunction[0] + delays[1] * mappingFunction[1];
}
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> T pathDelay(final T elevation, final FieldGeodeticPoint<T> point,
final T[] parameters, final FieldAbsoluteDate<T> date) {
// zenith delay
final T[] delays = computeZenithDelay(point, parameters, date);
// mapping function
final T[] mappingFunction = mappingFactors(elevation, point, date);
// Tropospheric path delay
return delays[0].multiply(mappingFunction[0]).add(delays[1].multiply(mappingFunction[1]));
}
/** This method allows the computation of the zenith hydrostatic and
* zenith wet delay. The resulting element is an array having the following form:
* <ul>
* <li>T[0] = D<sub>hz</sub> → zenith hydrostatic delay
* <li>T[1] = D<sub>wz</sub> → zenith wet delay
* </ul>
* @param point station location
* @param parameters tropospheric model parameters
* @param date current date
* @return a two components array containing the zenith hydrostatic and wet delays.
*/
public double[] computeZenithDelay(final GeodeticPoint point, final double[] parameters, final AbsoluteDate date) {
return zenithDelay.clone();
}
/** This method allows the computation of the zenith hydrostatic and
* zenith wet delay. The resulting element is an array having the following form:
* <ul>
* <li>T[0] = D<sub>hz</sub> → zenith hydrostatic delay
* <li>T[1] = D<sub>wz</sub> → zenith wet delay
* </ul>
* @param <T> type of the elements
* @param point station location
* @param parameters tropospheric model parameters
* @param date current date
* @return a two components array containing the zenith hydrostatic and wet delays.
*/
public <T extends CalculusFieldElement<T>> T[] computeZenithDelay(final FieldGeodeticPoint<T> point, final T[] parameters,
final FieldAbsoluteDate<T> date) {
final Field<T> field = date.getField();
final T zero = field.getZero();
final T[] delays = MathArrays.buildArray(field, 2);
delays[0] = zero.add(zenithDelay[0]);
delays[1] = zero.add(zenithDelay[1]);
return delays;
}
/** {@inheritDoc} */
@Override
public double[] mappingFactors(final double elevation, final GeodeticPoint point,
final AbsoluteDate date) {
// Day of year computation
final DateTimeComponents dtc = date.getComponents(utc);
final int dofyear = dtc.getDate().getDayOfYear();
// General constants | Hydrostatic part
final double bh = 0.0029;
final double c0h = 0.062;
final double c10h;
final double c11h;
final double psi;
// Latitude of the station
final double latitude = point.getLatitude();
// sin(latitude) > 0 -> northern hemisphere
if (FastMath.sin(latitude) > 0) {
c10h = 0.001;
c11h = 0.005;
psi = 0;
} else {
c10h = 0.002;
c11h = 0.007;
psi = FastMath.PI;
}
// Temporal factor
double t0 = 28;
if (latitude < 0) {
// southern hemisphere: t0 = 28 + an integer half of year
t0 += 183;
}
// Compute hydrostatique coefficient c
final double coef = ((dofyear - t0) / 365) * 2 * FastMath.PI + psi;
final double ch = c0h + ((FastMath.cos(coef) + 1) * (c11h / 2) + c10h) * (1 - FastMath.cos(latitude));
// General constants | Wet part
final double bw = 0.00146;
final double cw = 0.04391;
final double[] function = new double[2];
function[0] = TroposphericModelUtils.mappingFunction(coefficientsA[0], bh, ch, elevation);
function[1] = TroposphericModelUtils.mappingFunction(coefficientsA[1], bw, cw, elevation);
// Apply height correction
final double correction = TroposphericModelUtils.computeHeightCorrection(elevation, point.getAltitude());
function[0] = function[0] + correction;
return function;
}
/** {@inheritDoc} */
@Override
public <T extends CalculusFieldElement<T>> T[] mappingFactors(final T elevation, final FieldGeodeticPoint<T> point,
final FieldAbsoluteDate<T> date) {
final Field<T> field = date.getField();
final T zero = field.getZero();
// Day of year computation
final DateTimeComponents dtc = date.getComponents(utc);
final int dofyear = dtc.getDate().getDayOfYear();
// General constants | Hydrostatic part
final T bh = zero.add(0.0029);
final T c0h = zero.add(0.062);
final T c10h;
final T c11h;
final T psi;
// Latitude and longitude of the station
final T latitude = point.getLatitude();
// sin(latitude) > 0 -> northern hemisphere
if (FastMath.sin(latitude.getReal()) > 0) {
c10h = zero.add(0.001);
c11h = zero.add(0.005);
psi = zero;
} else {
c10h = zero.add(0.002);
c11h = zero.add(0.007);
psi = zero.getPi();
}
// Compute hydrostatique coefficient c
// Temporal factor
double t0 = 28;
if (latitude.getReal() < 0) {
// southern hemisphere: t0 = 28 + an integer half of year
t0 += 183;
}
final T coef = psi.add(zero.getPi().multiply(2.0).multiply((dofyear - t0) / 365));
final T ch = c11h.divide(2.0).multiply(FastMath.cos(coef).add(1.0)).add(c10h).multiply(FastMath.cos(latitude).negate().add(1.)).add(c0h);
// General constants | Wet part
final T bw = zero.add(0.00146);
final T cw = zero.add(0.04391);
final T[] function = MathArrays.buildArray(field, 2);
function[0] = TroposphericModelUtils.mappingFunction(zero.add(coefficientsA[0]), bh, ch, elevation);
function[1] = TroposphericModelUtils.mappingFunction(zero.add(coefficientsA[1]), bw, cw, elevation);
// Apply height correction
final T correction = TroposphericModelUtils.computeHeightCorrection(elevation, point.getAltitude(), field);
function[0] = function[0].add(correction);
return function;
}
/** {@inheritDoc} */
@Override
public List<ParameterDriver> getParametersDrivers() {
return Collections.emptyList();
}
}