i.landsat.acca(1grass) GRASS GIS User's Manual i.landsat.acca(1grass)
NAME
i.landsat.acca - Performs Landsat TM/ETM+ Automatic Cloud Cover As-
sessment (ACCA).
KEYWORDS
imagery, ACCA, cloud detection, satellite, Landsat
SYNOPSIS
i.landsat.acca
i.landsat.acca --help
i.landsat.acca [-5fx2s] input=basename output=name [b56compos-
ite=float] [b45ratio=float] [histogram=integer] [--overwrite]
[--help] [--verbose] [--quiet] [--ui]
Flags:
-5
Data is Landsat-5 TM
I.e. Thermal band is ’.6’ not ’.61’)
-f
Apply post-processing filter to remove small holes
-x
Always use cloud signature (step 14)
-2
Bypass second-pass processing, and merge warm (not ambiguous) and
cold clouds
-s
Include a category for cloud shadows
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog
Parameters:
input=basename [required]
Base name of input raster bands
Example: ’B.’ for B.1, B.2, ...
output=name [required]
Name for output raster map
b56composite=float
B56composite (step 6)
Default: 225.
b45ratio=float
B45ratio: Desert detection (step 10)
Default: 1.
histogram=integer
Number of classes in the cloud temperature histogram
Default: 100
DESCRIPTION
i.landsat.acca implements the Automated Cloud-Cover Assessment (ACCA)
Algorithm from Irish (2000) with the constant values for pass filter
one from Irish et al. (2006). To do this, it needs Landsat band numbers
2, 3, 4, 5, and 6 (or band 61 for Landsat-7 ETM+) which have already
been processed from DN into reflectance and band-6 temperature with
i.landsat.toar).
The ACCA algorithm gives good results over most of the planet with the
exception of ice sheets because ACCA operates on the premise that
clouds are colder than the land surface they cover. The algorithm was
designed for Landsat-7 ETM+ but because reflectance is used it is also
useful for Landsat-4/5 TM.
NOTES
i.landsat.acca works in the current region settings.
EXAMPLES
Run the standard ACCA algorithm with filling of small cloud holes (the
-f flag): With per-band reflectance raster maps named 226_62.toar.1,
226_62.toar.2, [...] and LANDSAT-7 thermal band 226_62.toar.61, out-
putting to a new raster map named 226_62.acca:
i.landsat.toar sensor=7 gain=HHHLHLHHL date=2003-04-07 \
product_date=2008-11-27 band_prefix=226_62 solar_elevation=49.51654
i.landsat.acca -f band_prefix=226_62.toar output=226_62.acca
REFERENCES
1 Irish R.R., Barker J.L., Goward S.N., and Arvidson T., 2006.
Characterization of the Landsat-7 ETM+ Automated Cloud-Cover As-
sessment (ACCA) Algorithm. Photogrammetric Engineering and Re-
mote Sensing vol. 72(10): 1179-1188.
2 Irish, R.R., 2000. Landsat 7 Automatic Cloud Cover Assessment.
In S.S. Shen and M.R. Descour (Eds.): Algorithms for Multispec-
tral, Hyperspectral, and Ultraspectral Imagery VI. Proceedings
of SPIE, 4049: 348-355.
SEE ALSO
i.atcorr, i.landsat.toar
AUTHOR
E. Jorge Tizado (ej.tizado unileon es), Dept. Biodiversity and Envi-
ronmental Management, University of León, Spain
SOURCE CODE
Available at: i.landsat.acca source code (history)
Accessed: unknown
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