i.landsat.accagrass - Online in the Cloud

PROGRAM:

NAME

i.landsat.acca - Performs Landsat TM/ETM+ Automatic Cloud Cover Assessment (ACCA).

KEYWORDS

imagery, Landsat, ACCA, cloud detection

SYNOPSIS

i.landsat.acca
i.landsat.acca --help
i.landsat.acca [-5fx2s] input=basename output=name [b56composite=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, outputting 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 Assessment (ACCA) Algorithm.
Photogrammetric Engineering and Remote 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 Multispectral, Hyperspectral, and Ultraspectral
Imagery VI. Proceedings of SPIE, 4049: 348-355.

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