[GRASS-user] cloud cover removal from LANDSAT data

[Sylvain Maillard]

> yes thanks, that looks great. The man page does not talk about it beyond
> a filename in the example, but does it need to be processed with
> i.landsat.toar before running i.landsat.acca? i.e. does it want derived
> temperatures instead of raw DNs? With DNs it exits with an error that it
> wants DCELL maps. (if temp, probably FCELL would be ok too, as the
> instrument is not that precise)
>

as mentionned in the description.html, i.landsat.acca work with reflectance
and temperature, so you have to use i.landsat.toar before i.landsat.acca

how do the i.landsat.acca, i.landsat.dehaze, and i.landsat.toar addon
> modules fit in/overlap with the i.atcorr module?
>

i.lansdat.dehaze make just a "light" athmospheric correction
i.attcorr do atmospheric correction using the 6S algorythm wich is much more
efficient, but need some extra parameters, and also work with several type
of capters
so you have to use i.landsat.dehaze OR i.attcorr

i.landsat.toar convert DN to radiance/reflectance and temparature
i.landsat.acca compute a cloud mask


also the acca man page does not really explain what benefit the 2-pass
> mode gives and what the -f flag does. ?
>

i think you can find all the explanations you can need about the way it's
working on the dedicated paper:
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
http://www.asprs.org/publications/pers/2006journal/october/2006_oct_1179-1188.pdf


regards,
Sylvain
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