Opened 6 years ago

Last modified 3 years ago

#3283 new enhancement

i.landsat.acca - cloud/shadow detection (vs. fmask)

Reported by: martinl Owned by: grass-dev@…
Priority: normal Milestone: 7.8.3
Component: Imagery Version: unspecified
Keywords: i.landsat.acca Cc:
CPU: Unspecified Platform: Unspecified

Description (last modified by martinl)

Recently I was working with Landsat data and performed cloud detection using G72:i.landsat.acca. The module produced quite reasonable results at least for clouds (see attachment:landsat_acca.png, yellow color), but much more worst results for shadows (orange color, see -s flag (1)), also -2f flags have been used. Please compare with RGB composition (attachment:landsat_rgb.png and attachment:landsat_acca_comp.png).

The module uses basically map algebra for cloud detection (2) and for shadows (3). Shadows detection seems to be somehow unfinished (or very simple).

I tested fmask (4) which gives much more better results (attachment:landsat_fmask.png, attachment:landsat_fmask_comp.png). I didn't studied the algorithm, but it seems to me that it's based on object segmentation approach.

Do you think that new better implementation of G72:i.landsat.acca would be topic for GSOC or student project? The fmask algorithm seems to be well-known, I also found Python library (5).

For now I would suggest to disable shadow detection or at least to add big fat warning about results. What do you think?

(1) https://grass.osgeo.org/grass72/manuals/i.landsat.acca.html

(2) https://trac.osgeo.org/grass/browser/grass/trunk/imagery/i.landsat.acca/algorithm.c#L76

(3) https://trac.osgeo.org/grass/browser/grass/trunk/imagery/i.landsat.acca/algorithm.c#L465

(4) https://github.com/prs021/fmask/blob/master/README.md

(5) http://pythonfmask.org/en/latest/

Attachments (5)

landsat_rgb.png (310.0 KB ) - added by martinl 6 years ago.
landsat_fmask_comp.png (236.3 KB ) - added by martinl 6 years ago.
landsat_acca_comp.png (277.4 KB ) - added by martinl 6 years ago.
landsat_acca.png (42.4 KB ) - added by martinl 6 years ago.
landsat_fmask.png (19.1 KB ) - added by martinl 6 years ago.

Download all attachments as: .zip

Change History (17)

by martinl, 6 years ago

Attachment: landsat_rgb.png added

by martinl, 6 years ago

Attachment: landsat_fmask_comp.png added

by martinl, 6 years ago

Attachment: landsat_acca_comp.png added

by martinl, 6 years ago

Attachment: landsat_acca.png added

by martinl, 6 years ago

Attachment: landsat_fmask.png added

comment:1 by martinl, 6 years ago

Description: modified (diff)

comment:2 by martinl, 6 years ago

Description: modified (diff)

comment:3 by neteler, 5 years ago

Milestone: 7.4.07.4.1

Ticket retargeted after milestone closed

comment:4 by neteler, 4 years ago

Milestone: 7.4.17.4.2

comment:5 by martinl, 4 years ago

Milestone: 7.4.27.6.0

All enhancement tickets should be assigned to 7.6 milestone.

comment:6 by martinl, 4 years ago

Milestone: 7.6.07.6.1

Ticket retargeted after milestone closed

comment:7 by martinl, 4 years ago

Milestone: 7.6.17.6.2

Ticket retargeted after milestone closed

comment:8 by martinl, 4 years ago

Milestone: 7.6.27.8.0

comment:9 by neteler, 3 years ago

Milestone: 7.8.07.8.1

Ticket retargeted after milestone closed

comment:10 by neteler, 3 years ago

Milestone: 7.8.17.8.2

Ticket retargeted after milestone closed

comment:11 by neteler, 3 years ago

Milestone: 7.8.2

Ticket retargeted after milestone closed

comment:12 by neteler, 3 years ago

Milestone: 7.8.3
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