Package org.esa.snap.core.util.math

Class RsMathUtils

java.lang.Object

org.esa.snap.core.util.math.RsMathUtils

public class RsMathUtils
extends Object

A utility class providing a set of mathematical functions frequently used in the fields of remote sensing.

All functions have been implemented with extreme caution in order to provide a maximum performance.

Field Summary

Fields

Modifier and Type	Field	Description
static double	BAROMETRIC_CONST	A constant used for the barometric formula - normalize to input in hPa.
static double	DEG_PER_RAD	A constant used for radian/degree conversions.
static double	GRAVITY_ACC	The earth's gravity acceleration in m / s^2.
static float	KOSCHMIEDER_CONST	The constant in Koschmieder's Formula.
static double	MEAN_EARTH_RADIUS	The Earth's mean radius in meters.
static double	RAD_PER_DEG	A constant used for degree/radian conversions.
static double	SPEC_WEIGHT_AIR	The specific weight of air in kg / m^3 It's value is 1.26895.

Constructor Summary

Constructors

Constructor	Description
RsMathUtils()

Method Summary

Modifier and Type	Method	Description
static void	applyGeodeticCorrection(GeoPos gp, double h, double vz, double va)	Applies a geodetic correction to the given geographical coordinate.
static float	elevationToZenith(float elevation)	Converts an elevation angle to a zenith angle.
static float[]	elevationToZenith(float[] elevation, float[] recycle)	Converts a vector of elevation angles to a vector of zenith angles.
static float	koschmieder(float visibility)	Transforms horizontal visibility(km) to aerosol optical depth according to Koschmieder's formula.
static float	koschmiederInv(float opticalDepth)	Transforms aerosol optical depth to horizontal visibility(km) according to Koschmieder's formula.
static float[]	radianceToReflectance(float[] rad, float[] sza, float e0, float[] recycle)	Converts an array of radiance values to an array of reflectance values for given solar spectral flux and sun zenith angle.
static float	radianceToReflectance(float rad, float sza, float e0)	Converts a radiance value to a reflectance value for given solar spectral flux and sun zenith angle.
static float	reflectanceToRadiance(float refl, float sza, float e0)	Converts a reflectance value to a radiance value for given solar spectral flux and sun zenith angle.
static float[]	simpleBarometric(float[] seaPress, float[] height, float[] recycle)	Calculates the air pressure in a given height given the sea level air pressure.
static float	simpleBarometric(float seaPress, float height)	Calculates the air pressure in a given height given the sea level air pressure.
static float	zenithToElevation(float zenith)	Converts a zenith angle to an elevation angle.
static float[]	zenithToElevation(float[] zenith, float[] recycle)	Converts a vector of zenith angles to a vector of elevation angles.

Methods inherited from class java.lang.Object

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

Field Detail

SPEC_WEIGHT_AIR

public static final double SPEC_WEIGHT_AIR

The specific weight of air in kg / m^3 It's value is 1.26895.

See Also:

Constant Field Values

GRAVITY_ACC

public static final double GRAVITY_ACC

The earth's gravity acceleration in m / s^2. It's value is 9.80665.

See Also:

Constant Field Values

BAROMETRIC_CONST

public static final double BAROMETRIC_CONST

A constant used for the barometric formula - normalize to input in hPa. It's value is GRAVITY_ACC * SPEC_WEIGHT_AIR * 1e-2.

See Also:

Constant Field Values

KOSCHMIEDER_CONST

public static final float KOSCHMIEDER_CONST

The constant in Koschmieder's Formula. It's value is 3.92 * 2.

See Also:

Constant Field Values

RAD_PER_DEG

public static final double RAD_PER_DEG

A constant used for degree/radian conversions. It's value is Math.PI / 180.0.

See Also:

Constant Field Values

DEG_PER_RAD

public static final double DEG_PER_RAD

A constant used for radian/degree conversions. It's value is 180.0 / Math.PI.

See Also:

Constant Field Values

MEAN_EARTH_RADIUS

public static final double MEAN_EARTH_RADIUS

The Earth's mean radius in meters.

See Also:

Constant Field Values

Constructor Detail

RsMathUtils

public RsMathUtils()

Method Detail

reflectanceToRadiance

public static float reflectanceToRadiance(float refl,
                                          float sza,
                                          float e0)

Converts a reflectance value to a radiance value for given solar spectral flux and sun zenith angle. This is the inverse of radianceToReflectance.

Parameters:

refl - the reflectance

sza - the sun zenith angle in decimal degrees

e0 - the solar spectral flux in mW / (m^2 * sr * nm)

Returns:

the corresponding radiance in mW /(m^2 * sr * nm)

radianceToReflectance

public static float radianceToReflectance(float rad,
                                          float sza,
                                          float e0)

Converts a radiance value to a reflectance value for given solar spectral flux and sun zenith angle.

Parameters:

rad - the radiance in mW /(m^2 * sr * nm)

sza - the sun zenith angle in decimal degrees

e0 - the solar spectral flux in mW / (m^2 * sr * nm)

Returns:

the corresponding reflectance

radianceToReflectance

public static float[] radianceToReflectance(float[] rad,
                                            float[] sza,
                                            float e0,
                                            float[] recycle)

Converts an array of radiance values to an array of reflectance values for given solar spectral flux and sun zenith angle.

If the recycle parameter is of the same size as the radiance array, this array will be filled with the results and returned. The returned result may contain reflectances <0 or >1.

The method performs no plausability check on the conversion.

Parameters:

rad - the radiances in mW /(m^2 * sr * nm)

sza - the sun zenith angle in decimal degrees

e0 - the solar spectral flux

recycle - optional array which will be filled with the results, can be null.

Returns:

the array of corresponding reflectance

zenithToElevation

public static float zenithToElevation(float zenith)

Converts a zenith angle to an elevation angle.

Parameters:

zenith - the zenith angle in decimal degrees

zenithToElevation

public static float[] zenithToElevation(float[] zenith,
                                        float[] recycle)

Converts a vector of zenith angles to a vector of elevation angles. If recycle is not null and has the same size as the zenith angle vector, recycle will be filled and returned to minimize the memory finmgerprint.

Parameters:

zenith - the zenith angle vector in decimal degrees

recycle - optional array which will be filled with the results. can be null.

elevationToZenith

public static float elevationToZenith(float elevation)

Converts an elevation angle to a zenith angle. Convenience routine. Does the same as zenithToElevation but for code clarity ...

Parameters:

elevation - the lelevation angle in decimal degrees

elevationToZenith

public static float[] elevationToZenith(float[] elevation,
                                        float[] recycle)

Converts a vector of elevation angles to a vector of zenith angles. If recycle is not null and has the same size as the elevation angle vector, recycle will be filled and returned to minimize the memory fingerprint. Convenience routine. Does the same as zenithToElevation but for code clarity ...

Parameters:

elevation - a vector of elevation angles (in degree)

recycle - optional array which will be filled with the results. can be null.

simpleBarometric

public static float simpleBarometric(float seaPress,
                                     float height)

Calculates the air pressure in a given height given the sea level air pressure. Simple version with no dependency on temperature etc...

Parameters:

seaPress - the sea level air pressure in hPa

height - the height above sea level in m

simpleBarometric

public static float[] simpleBarometric(float[] seaPress,
                                       float[] height,
                                       float[] recycle)

Calculates the air pressure in a given height given the sea level air pressure. Simple version with no dependency on temperature etc... This method processes on vectors. If recycle is not null and has the same size as the sea pressure vector, recycle will be filled and returned to minimize the memory fingerprint.

Parameters:

seaPress - vector of sea level air pressure in hPa

height - vector of height above sea level in m

recycle - optional array which will be filled with the results. can be null.

koschmieder

public static float koschmieder(float visibility)

Transforms horizontal visibility(km) to aerosol optical depth according to Koschmieder's formula.

Parameters:

visibility - horizontal visibility in km

Throws:

IllegalArgumentException - if the given parameter is 0.f

koschmiederInv

public static float koschmiederInv(float opticalDepth)

Transforms aerosol optical depth to horizontal visibility(km) according to Koschmieder's formula.

Parameters:

opticalDepth - aerosol optical depth

Throws:

IllegalArgumentException - if the given parameter is 0.f

applyGeodeticCorrection

public static void applyGeodeticCorrection(GeoPos gp,
                                           double h,
                                           double vz,
                                           double va)

Applies a geodetic correction to the given geographical coordinate.

The implementation assumes that the Earth is flat at the given coordinate point at elevetion zero and at the given elevation. Furthermore the earth is assumed to be a sphere with the fixed radius MEAN_EARTH_RADIUS.

Parameters:

gp - the geographical coordinate to be corrected and which will be corrected

h - elevation above the Earth's sphere or ellipsoid surface in meters

vz - satellite viewing zenith angle in degree

va - satellite viewing azimuth angle in degree