org.orekit.models.earth.troposphere

Class SaastamoinenModel

java.lang.Object

org.orekit.models.earth.troposphere.SaastamoinenModel

All Implemented Interfaces:

DiscreteTroposphericModel, MappingFunction

public class SaastamoinenModel
extends Object
implements DiscreteTroposphericModel

The modified Saastamoinen model. Estimates the path delay imposed to electro-magnetic signals by the troposphere according to the formula:

 δ = 2.277e-3 / cos z * (P + (1255 / T + 0.05) * e - B * tan²
 z) + δR
 

with the following input data provided to the model:

• z: zenith angle
• P: atmospheric pressure
• T: temperature
• e: partial pressure of water vapour
• B, δR: correction terms

The model supports custom δR correction terms to be read from a configuration file (saastamoinen-correction.txt) via the DataProvidersManager.

Author:

Thomas Neidhart

See Also:

"Guochang Xu, GPS - Theory, Algorithms and Applications, Springer, 2007"

Field Summary

Fields

Modifier and Type	Field and Description
static double	DEFAULT_LOW_ELEVATION_THRESHOLD Default lowest acceptable elevation angle [rad].
static String	DELTA_R_FILE_NAME Default file name for δR correction term table.

Constructor Summary

Constructors

Constructor and Description
SaastamoinenModel(double t0, double p0, double r0) Create a new Saastamoinen model for the troposphere using the given environmental conditions and table from the reference book.
SaastamoinenModel(double t0, double p0, double r0, String deltaRFileName) Create a new Saastamoinen model for the troposphere using the given environmental conditions.
SaastamoinenModel(double t0, double p0, double r0, String deltaRFileName, DataProvidersManager dataProvidersManager) Create a new Saastamoinen model for the troposphere using the given environmental conditions.

Method Summary

Modifier and Type	Method and Description
double[]	computeZenithDelay(double height, double[] parameters, AbsoluteDate date) This method allows the computation of the zenith hydrostatic and zenith wet delay.
<T extends RealFieldElement<T>> T[]	computeZenithDelay(T height, T[] parameters, FieldAbsoluteDate<T> date) This method allows the computation of the zenith hydrostatic and zenith wet delay.
double	getLowElevationThreshold() Get the low elevation threshold value for path delay computation.
List<ParameterDriver>	getParametersDrivers() Get the drivers for tropospheric model parameters.
static SaastamoinenModel	getStandardModel() Create a new Saastamoinen model using a standard atmosphere model.
double[]	mappingFactors(double elevation, double height, double[] parameters, AbsoluteDate date) This method allows the computation of the hydrostatic and wet mapping functions.
<T extends RealFieldElement<T>> T[]	mappingFactors(T elevation, T height, T[] parameters, FieldAbsoluteDate<T> date) This method allows the computation of the hydrostatic and wet mapping functions.
double	pathDelay(double elevation, double height, double[] parameters, AbsoluteDate date) Calculates the tropospheric path delay for the signal path from a ground station to a satellite.
<T extends RealFieldElement<T>> T	pathDelay(T elevation, T height, T[] parameters, FieldAbsoluteDate<T> date) Calculates the tropospheric path delay for the signal path from a ground station to a satellite.
void	setLowElevationThreshold(double lowElevationThreshold) Set the low elevation threshold value for path delay computation.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.orekit.models.earth.troposphere.MappingFunction

getParameters, getParameters

Field Detail

DELTA_R_FILE_NAME

public static final String DELTA_R_FILE_NAME

Default file name for δR correction term table.

See Also:

Constant Field Values

DEFAULT_LOW_ELEVATION_THRESHOLD

public static final double DEFAULT_LOW_ELEVATION_THRESHOLD

Default lowest acceptable elevation angle [rad].

See Also:

Constant Field Values

Constructor Detail

SaastamoinenModel

public SaastamoinenModel(double t0,
                         double p0,
                         double r0)

Create a new Saastamoinen model for the troposphere using the given environmental conditions and table from the reference book.

Parameters:

t0 - the temperature at the station [K]

p0 - the atmospheric pressure at the station [mbar]

r0 - the humidity at the station [fraction] (50% -> 0.5)

Since:

10.1

See Also:

SaastamoinenModel(double, double, double, String, DataProvidersManager)

SaastamoinenModel

@DefaultDataContext
public SaastamoinenModel(double t0,
                                             double p0,
                                             double r0,
                                             String deltaRFileName)

Create a new Saastamoinen model for the troposphere using the given environmental conditions. This constructor uses the default data context if deltaRFileName != null.

Parameters:

t0 - the temperature at the station [K]

p0 - the atmospheric pressure at the station [mbar]

r0 - the humidity at the station [fraction] (50% -> 0.5)

deltaRFileName - regular expression for filename containing δR correction term table (typically DELTA_R_FILE_NAME), if null default values from the reference book are used

Since:

7.1

See Also:

SaastamoinenModel(double, double, double, String, DataProvidersManager)

SaastamoinenModel

public SaastamoinenModel(double t0,
                         double p0,
                         double r0,
                         String deltaRFileName,
                         DataProvidersManager dataProvidersManager)

Create a new Saastamoinen model for the troposphere using the given environmental conditions. This constructor allows the user to specify the source of of the δR file.

Parameters:

t0 - the temperature at the station [K]

p0 - the atmospheric pressure at the station [mbar]

r0 - the humidity at the station [fraction] (50% -> 0.5)

deltaRFileName - regular expression for filename containing δR correction term table (typically DELTA_R_FILE_NAME), if null default values from the reference book are used

dataProvidersManager - provides access to auxiliary data.

Since:

10.1

Method Detail

getStandardModel

public static SaastamoinenModel getStandardModel()

Create a new Saastamoinen model using a standard atmosphere model.

• temperature: 18 degree Celsius
• pressure: 1013.25 mbar
• humidity: 50%

Returns:

a Saastamoinen model with standard environmental values

pathDelay

public double pathDelay(double elevation,
                        double height,
                        double[] parameters,
                        AbsoluteDate date)

Calculates the tropospheric path delay for the signal path from a ground station to a satellite.

The Saastamoinen model is not defined for altitudes below 0.0. for continuity reasons, we use the value for h = 0 when altitude is negative.

There are also numerical issues for elevation angles close to zero. For continuity reasons, elevations lower than a threshold will use the value obtained for the threshold itself.

Specified by:

pathDelay in interface DiscreteTroposphericModel

Parameters:

elevation - the elevation of the satellite, in radians

height - the height of the station in m above sea level

parameters - tropospheric model parameters.

date - current date

Returns:

the path delay due to the troposphere in m

See Also:

getLowElevationThreshold(), setLowElevationThreshold(double)

pathDelay

public <T extends RealFieldElement<T>> T pathDelay(T elevation,
                                                   T height,
                                                   T[] parameters,
                                                   FieldAbsoluteDate<T> date)

Calculates the tropospheric path delay for the signal path from a ground station to a satellite.

The Saastamoinen model is not defined for altitudes below 0.0. for continuity reasons, we use the value for h = 0 when altitude is negative.

There are also numerical issues for elevation angles close to zero. For continuity reasons, elevations lower than a threshold will use the value obtained for the threshold itself.

Specified by:

pathDelay in interface DiscreteTroposphericModel

Type Parameters:

T - type of the elements

Parameters:

elevation - the elevation of the satellite, in radians

height - the height of the station in m above sea level

parameters - tropospheric model parameters.

date - current date

Returns:

the path delay due to the troposphere in m

See Also:

getLowElevationThreshold(), setLowElevationThreshold(double)

computeZenithDelay

public double[] computeZenithDelay(double height,
                                   double[] parameters,
                                   AbsoluteDate date)

Description copied from interface: DiscreteTroposphericModel

This method allows the computation of the zenith hydrostatic and zenith wet delay. The resulting element is an array having the following form:

• double[0] = D_hz → zenith hydrostatic delay
• double[1] = D_wz → zenith wet delay

Specified by:

computeZenithDelay in interface DiscreteTroposphericModel

Parameters:

height - the height of the station in m above sea level.

parameters - tropospheric model parameters.

date - current date

Returns:

a two components array containing the zenith hydrostatic and wet delays.

computeZenithDelay

public <T extends RealFieldElement<T>> T[] computeZenithDelay(T height,
                                                              T[] parameters,
                                                              FieldAbsoluteDate<T> date)

Description copied from interface: DiscreteTroposphericModel

This method allows the computation of the zenith hydrostatic and zenith wet delay. The resulting element is an array having the following form:

• T[0] = D_hz → zenith hydrostatic delay
• T[1] = D_wz → zenith wet delay

Specified by:

computeZenithDelay in interface DiscreteTroposphericModel

Type Parameters:

T - type of the elements

Parameters:

height - the height of the station in m above sea level.

parameters - tropospheric model parameters.

date - current date

Returns:

a two components array containing the zenith hydrostatic and wet delays.

mappingFactors

public double[] mappingFactors(double elevation,
                               double height,
                               double[] parameters,
                               AbsoluteDate date)

Description copied from interface: MappingFunction

This method allows the computation of the hydrostatic and wet mapping functions. The resulting element is an array having the following form:

• double[0] = m_h(e) → hydrostatic mapping function
• double[1] = m_w(e) → wet mapping function

Specified by:

mappingFactors in interface MappingFunction

Parameters:

elevation - the elevation of the satellite, in radians.

height - the height of the station in m above sea level.

parameters - tropospheric model parameters.

date - current date

Returns:

a two components array containing the hydrostatic and wet mapping functions.

mappingFactors

public <T extends RealFieldElement<T>> T[] mappingFactors(T elevation,
                                                          T height,
                                                          T[] parameters,
                                                          FieldAbsoluteDate<T> date)

Description copied from interface: MappingFunction

This method allows the computation of the hydrostatic and wet mapping functions. The resulting element is an array having the following form:

• T[0] = m_h(e) → hydrostatic mapping function
• T[1] = m_w(e) → wet mapping function

Specified by:

mappingFactors in interface MappingFunction

Type Parameters:

T - type of the elements

Parameters:

elevation - the elevation of the satellite, in radians.

height - the height of the station in m above sea level.

parameters - tropospheric model parameters.

date - current date

Returns:

a two components array containing the hydrostatic and wet mapping functions.

getParametersDrivers

public List<ParameterDriver> getParametersDrivers()

Description copied from interface: MappingFunction

Get the drivers for tropospheric model parameters.

Specified by:

getParametersDrivers in interface MappingFunction

Returns:

drivers for tropospheric model parameters

getLowElevationThreshold

public double getLowElevationThreshold()

Get the low elevation threshold value for path delay computation.

Returns:

low elevation threshold, in rad.

Since:

10.2

See Also:

pathDelay(double, double, double[], AbsoluteDate), pathDelay(RealFieldElement, RealFieldElement, RealFieldElement[], FieldAbsoluteDate)

setLowElevationThreshold

public void setLowElevationThreshold(double lowElevationThreshold)

Set the low elevation threshold value for path delay computation.

Parameters:

lowElevationThreshold - The new value for the threshold [rad]

Since:

10.2

See Also:

pathDelay(double, double, double[], AbsoluteDate), pathDelay(RealFieldElement, RealFieldElement, RealFieldElement[], FieldAbsoluteDate)