[GRASS-user] Estimating Albedo from Landsat

[Nikos Alexandris]

Nikos:
...
> Downloaded:
> - extra: LT50160351988258XXX03 (includes visible clouds - maybe good for
> testing?)

# import landsat bands in wgs84, utm, zone 17
# r.proj to nc_spm_08/landsat
# set region
g.region rast=lsat5_1988.1 -p

projection: 99 (Lambert Conformal Conic)
zone:       0
datum:      nad83
ellipsoid:  a=6378137 es=0.006694380022900787
north:      361770
south:      144750
west:       463950
east:       709530
nsres:      30
ewres:      30
rows:       7234
cols:       8186
cells:      59217524

# rgb colors for 742
i.landsat.rgb r=lsat5_1988.2 g=lsat5_1988.4 b=lsat5_1988.7 strength=96
d.rgb r=lsat5_1988.2 g=lsat5_1988.4 b=lsat5_1988.7 # obvious clouds

# toar
i.landsat.toar band_prefix=lsat5_1988 method=uncorrected sensor=5 
product_date=1988-09-14 date=1988-09-14 solar_elevation=48.6773844

# acca
i.landsat.acca -5f2 band_prefix=lsat5_1988.toar output=lsat5_1988.toar.acca

# how many cats?
r.info lsat5_1988.toar.acca -r
min=6
max=9

# draw only "acca" cat=6
d.erase black
d.rast lsat5_1988.toar.acca cat=6 -o


In the "acca" result:

- clouds are detected (cat=6), not that bad(ly) I suppose. Some filtering 
could push away the (rest of the) "noise". 

- obvious mis-detections (commission errors) found within
  - n=188310 s=168270 w=618870 e=636150 (bare ground? urban area? not sure 
about the confusing land cover/class here...)
  - n=219030 s=180510 w=646410 e=655740 (road)
  - in the borders due to the non-identical extent of all bands (!?)

- categories 7 and 8 seem to be empty, category 9 looks very messy

Could it be that non-cloudy acquisitions are mistreated by the algorithm? I 
can't clearly recognise clouds in the landsat scenes included in NC data set 
(both the 1987 and the 2000 scenes).

Will (then) the algorithm work (only) with (very) cloudy data?

Nikos