GENRLUT

Description

GENRLUT transforms a MODTRAN 4 "tape7" output file into an at-sensor radiance lookup table. The radiance units used are microwatts/cm^2/nm/sr. This function is designed to be used in combination with GENTP5.

Parameters

Name	Type	Caption	Length	Value range
RLUTFILO*	String	Output radiance LUT file name	1 - 192
DBOS	Integer	Output Radiance LUT segment	0 - 1
TAPE7*	String	Tape7 MODTRAN4 file name	1 - 192
VWVCINS	Float	Vertical water vapor column interval and samples	0 - 3	Default: 0.0,0.0,1.0
AODINS	Float	Aerosol optical depth range interval and samples	0 - 3
SMRINS	Float	Surface meteorological range interval and samples	0 - 3
REFLINS*	Float	Reflectance interval and samples	3 - 3
RAZINS*	Float	Relative view-solar azimuth interval and samples	3 - 3
VZAINS*	Float	View zenith angle interval and samples	3 - 3
SZAINS*	Float	Solar zenith angle interval and samples	3 - 3
ELEVINS*	Float	Scene elevation interval and samples	3 - 3
SALTINS*	Float	Sensor altitude Interval and samples	3 - 3

* Required parameter

Parameter descriptions

RLUTFILO

Specifies the name of the PCIDSK file to receive the output radiance LUT.

If no leading path is specified, the file is assumed to be located in the current working directory.

DBOS

Specifies the output segment to receive the generated at-sensor radiance lookup table.

Only one segment can be specified.

TAPE7

Specifies the name of the "tape7" MODTRAN4 file that contains the results from the MODTRAN4 execution.

VWVCINS

Specifies the vertical water vapor column interval endpoints (in g.cm^2) and the number of samples.

This setting must match the VWVCINS setting that was used for the related GENTP5 run. The default values are 0.0,0.0, and 1.0.

AODINS

Specifies the aerosol optical depth interval endpoints (at 550 nm) and the number of samples.

This setting must match the AODINS setting that was used for the related GENTP5 run.

The default values are 0.0,0.0, and 1.0, but only one of AODINS and SMRINS can be specified.

SMRINS

Specifies the surface meteorological range interval endpoints (in km) and the number of samples.

This setting must match the SMRINS setting that was used for the related GENTP5 run. The default values are 0.0,0.0, and 1.0, but only one of AODINS and SMRINS can be specified.

REFLINS

Specifies the reflectance interval endpoints (in percentage) and the number of samples.

This setting must match the REFLINS setting that was used for the related GENTP5 run.

RAZINS

Specifies the relative view-solar azimuth (solar azimuth minus view azimuth) interval endpoints (in degrees) and the number of samples.

This setting must match the RAZINS setting that was used for the related GENTP5 run.

VZAINS

Specifies the view zenith angle interval endpoints (in degrees) and the number of samples.

This setting must match the VZAINS setting that was used for the related GENTP5 run.

SZAINS

Specifies the solar zenith angle interval endpoints (in degrees) and the number of samples.

This setting must match the SZAINS setting that was used for the related GENTP5 run.

ELEVINS

Specifies the scene elevation interval endpoints (in meters with respect to the WGS84 vertical datum) and the number of samples.

This setting must match the ELEVINS setting that was used for the related GENTP5 run.

SALTINS

Specifies the sensor altitude interval endpoints (in meters with respect to the WGS84 vertical datum) and the number of samples.

This setting must match the SALTINS setting that was used for the related GENTP5 run.

Details

GENRLUT is designed to be used in combination with GENTP5 and the MODTRAN4 program from Ontar Corporation to produce a radiance lookup table (RLUT) for the atmospheric transformation of remotely sensed images. GENRLUT has been tested with Version 2, Revision 1 of the MODTRAN4 program.

The radiance units used in the generated RLUT are microwatts/cm^2/nm/sr.

The "tape7" file generated by the MODTRAN4 program contains the results of one or more MODTRAN4 runs. GENRLUT transforms this file into an RLUT.

RLUT format

The radiance lookup table (RLUT) is a 9-dimensional array. An RLUT table entry is a pair of real values: Lg, the at-sensor radiance reflected by the target, and Lo, the at-sensor radiance due to all other sources including atmospheric scattering, adjacency effects, and thermally generated radiation.

Each RLUT dimension is labeled according to the physical quantity that it represents. Each dimension corresponds to a physical quantity for which an interval and number of samples was specified in the GENTP5 and GENRLUT runs:

Sensor altitude
Solar zenith angle
Reflectance
Surface meteorological range
Vertical water vapor column
Scene elevation
Relative view-solar azimuth
View zenith angle
Wavelength

One or more samples are identified on each dimension. The number of samples along a given dimension and the coordinates of those values correspond to the "interval and number of samples" parameter values used for the matching physical quantity in the GENTP5 and GENRLUT runs.

An RLUT is stored exclusively in a PCIDSK binary segment. One RLUT can be stored per segment. All RLUT attributes are saved as metadata for that binary segment.

The following metadata tags are recognized by the RLUT processing algorithms:

HYLUTDimensions: specifies the number of dimensions for the LUT. This must always be 9 for RLUT.
HYLUTSize_?: the metadata tag is constructed by concatenating the dimension index to "HYLUTSize_"; for example, HYLUTSize_0, HYLUTSize_1, ..., HYLUTSize_8. Each metadata entry contains the dimension size for the specified dimension. These metadata tags are mandatory.
HYLUTLabel_?: the metadata tag is constructed by concatenating the dimension index to "HYLUTLabel_"; for example, HYLUTLabel_0, HYLUTLabel_1, ..., HYLUTLabel_8. Each metadata entry contains the label for the specified dimension. These metadata tags are optional.
HYLUTCoords_?: the metadata tag is constructed by concatenating the dimension index to "HYLUTCoords_"; for example, HYLUTCoords_0, HYLUTCoords_1, ..., HYLUTCoords_8. Each metadata entry contains a comma-separated list of coordinate values for each dimension entry. These metadata tags are optional for the sake of reading and displaying the RLUT data. If atmospheric correction is being applied, however, they are mandatory.
HYLUTElementSize: specifies the element size of an LUT entry in bytes. This must always be 8 for RLUT.

Upon saving the RLUT to disk, the RLUT entries are serialized into a system-independent byte stream and written to the binary segment.

Getting MODTRAN4

The MODTRAN4 CDROM and single-user license are available from Ontar Corporation (http://www.ontar.com/Software/pricing.aspx). PCI Geomatics has tested GENTP5 and GENRLUT with Version 2, Revision 1 of the MODTRAN4 software.

Example

This example shows a synthetic run of GENRLUT.

EASI>rlutfilo	=	"rlut.pix"
EASI>dbos	=	
EASI>tape7	=	"tape7"
EASI>vwvcins	=	
EASI>aodins	=	
EASI>smrins	=	
EASI>reflins	=	0.005,0.6,2
EASI>razins	=	-80.8,99.2,3
EASI>vzains	=	165,180,4
EASI>szains	=	14.4,14.4,1
EASI>elevins	=	1524,1524,1
EASI>saltins	=	21036,21036,1

EASI>run GENRLUT

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