SHFTCW

Description

Shifts the center wavelength values of the band response profiles for an input image data set.

Parameters

shftcw(file, cwshft, bandlist)

Name	Type	Caption	Length	Value range
FILE *	str	Input file name	1 -
CWSHFT *	List[float]	Center wavelength shift	1 - 16
BANDLIST	List[int]	Reference band list	0 - 16	1 -

* Required parameter

Parameter descriptions

FILE

Specifies the name of the file that contains the image data set to which the shifts are to be applied.

CWSHFT

Specifies a uniform shift to be applied to all bands, or up to 16 shifts to be applied to up to 16 individual bands specified with BANDLIST (Reference Band List). Shifts are specified in nanometers.

BANDLIST

Specifies the list of bands to which individual shifts will be applied.

Details

SHFTCW requires that the data set contain image metadata that includes a center wavelength value for each band.

The sensors used to acquire hyperspectral data are complex optomechanical devices that may be subjected to significant mechanical stresses. The significance of these stresses is that they may alter the band responses of the instrument relative to a previous laboratory calibration. In other words, the instrument may acquire data in wavebands that differ significantly from those determined for the sensor in the calibration. This is a concern especially in the case of airborne sensors that undergo stress from vibration, repeated landings, and installation/deinstallation.

A waveband shift as small as 2nm in the vicinity of an atmospheric absorption band may have a dramatic effect on reflectance estimates derived from the image data (Secker et. al., 2001).

SHFTCW provides a convenient means of applying corrective shifts to band center wavelength values included in the data set's metadata. These shifts may be determined by iteratively shifting image data and examining derived reflectance spectra (Secker et. al., 2001).

SHFTCW can apply a uniform shift to all bands in the data set, or specific shifts to individual bands (up to 16 at once).

Examples

Apply a -1.76nm shift to all bands of cuprad.pix:

from pci.shftcw import shftcw

file	=	"cuprad.pix"	# input file
cwshft	=	[-1.76]	# center wavelength shift
bandlist	=	[]	# reference band list

shftcw( file, cwshft, bandlist )

Apply a -0.53, -0.10, and 1.21nm shift to bands 23, 24, and 25 respectively:

from pci.shftcw import shftcw

file	=	"cuprad.pix"	# input file
cwshft	=	[-0.53,-0.10,1.21]	# center wavelength shift
bandlist	=	[23,24,25]	# reference bands

shftcw( file, cwshft, bandlist )

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 9F028-0-4902/12.

References

Jeff Secker, Karl Staenz, Robert P. Gauthier, and Paul Budkewitsch, Vicarious calibration of airborne hyperspectral sensors in operational environments, "Remote Sensing of Environment," Vol. 76, (2001), pp. 81-92.