RESRLUT

Description

Parameters

Parameter descriptions

RLUTFILI

Specifies the name of the file that contains the input radiance lookup table.

DBSRL

Specifies the input segment that contains the radiance LUT.

RLUTFILO

Specifies the name of the output radiance LUT file.

DBOS

Specifies the output segment to receive the resampled radiance LUT.

FILI

Specifies the name of the file that contains relative response profile metadata for the target sensor.

Details

RESRLUT is designed to be used together with GENTP5 and GENRLUT. It completes the RLUT processing suite by adding RLUT resampling capabilities.

RESRLUT resamples an at-sensor radiance lookup table along the wavelength dimension so that it coincides with a specified relative response profile.

RESRLUT first verifies all parameters and the validity of the RLUT. It then extracts the sensor band response profiles from the specified input file (FILI). The response profiles for all bands in the sensor definition are used, regardless of their associated band quality value. This is done because the quality of the image data stored in the data set (the data set's "band quality") is irrelevant to this operation.

RESRLUT then convolves each spectrum from the input radiance lookup table with the sensor band response profiles to produce a resampled spectrum where the wavelength samples align with the center wavelength values of the sensor. The resampled spectra are output to the specified output RLUT segment. If the output file does not already exist, a new one is created. If no output segment is specified, a new binary segment is created.

The RLUT cannot store spectrum quality values, and "plot" quality is assumed for all spectrum samples.

The total wavelength range of the input RLUT spectra can be less that that of the union of the band response profiles. In such a case, the resampled spectra will only have measurement values for the center wavelengths of band response profiles that encompass at least one input measurement value.

Example

This example demonstrates the resampling of a radiance lookup table generated using GENTP5 and GENRLUT.

Assume that you created the at-sensor radiance lookup table for cuprad.pix, as described in the example sections of GENTP5 and GENRLUT. To speed up execution time, resample the at-sensor radiance lookup table to match the sensor response profile of cuprad.pix, and save it as a new binary segment in rlut.pix.

EASI>rlutfili	=	"cuprad.pix"	! input RLUT file
EASI>dbsrl	=	2	! input RLUT segment
EASI>rlutfilo	=	"rlut.pix"	! output file
EASI>dbos	=		! new output segment 
EASI>fili	=	"cuprad.pix"	! relative response profile

EASI>run RESRLUT

Algorithm

RESRLUT calculates a convolution coefficient for each wavelength sample. The convolution coefficient for a wavelength sample is simply the value of the encompassing response profile at that wavelength. A response profile encompasses a wavelength sample if the wavelength sample falls within the full width at half maximum (FWHM) interval for that response profile.

If a wavelength sample does not fall within the FWHM interval for any response profile, linear interpolation of the neighboring samples is applied.

Let 'n' wavelength samples be encompassed by response profile 'b'. Let the convolution coefficient for the i'th wavelength sample encompassed by response profile 'b' be denoted by C_b,i. Let the measurement value in spectrum 's' for the i'th wavelength sample encompassed by response profile 'b' be denoted by M_s,b,i.

Denote the resampled measurement value for response profile b by R_b.

R_b is computed as:

s = Sum i=1,n (C_b,i)
a = Sum i=1,n (M_s,b,i * C_b,i)

then R_b = a / s

Acknowledgements

PCI Geomatics received financial support from the Canadian Space Agency/L'Agence Spatiale Canadienne through the Earth Observation Application Development Program (EOADP) for the development of this software, under contract 9F028-0-4914/09.

References

Berk, A. et al., 1999, "Modtran4 User's Manual", Air Force Research Laboratory, Space Vehicles Directorate, Air Force Materiel Command, Hanscom AFB, MA

Landgrebe, D.A., "Information Extraction Principles and Methods for Multispectral and Hyperspectral Image Data", Chapter 1 of Information Processing of Remote Sensing, World Scientific Publishing Co., River Edge N.J.