i.landsat.acca(1)

📦
version 8.4.2 · 8 versions
, in fedora 44

💖 i.landsat.acca — the vibe check on clouds 💖

okay bestie, so this is i.landsat.acca(1), straight out of the GRASS GIS User's Manual, and it's literally the girl who looks at satellite pics and goes "yeah that's a cloud." She's the Automated Cloud Cover Assessment — ACCA for short — and she ate. 🦋

✨ NAME ✨

i.landsat.acca — Performs Landsat TM/ETM+ Automatic Cloud Cover Assessment (ACCA). No cap, that's her whole job. 💅

🎀 KEYWORDS 🎀

imagery, ACCA, cloud detection, satellite, Landsat — the whole aesthetic, right there.

🌈 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: the little toggle girlies 🔥

  • -5 — Data is Landsat-5 TM. I.e. Thermal band is '.6' not '.61'. (yes the period matters, don't play with me 🙈)
  • -f — Apply post-processing filter to remove small holes. Little cloud pinholes? Gone. Not on my watch. 💅
  • -x — Always use cloud signature (step 14). Like, always. Committed. Main character energy. 👑
  • -2 — Bypass second-pass processing, and merge warm (not ambiguous) and cold clouds. Two passes? Not today. Merge them and go. 😭
  • -s — Include a category for cloud shadows. Shadows are content too. 🌸
  • --overwrite — Allow output files to overwrite existing files. She will absolutely bulldoze your old file, so watch it. 💀
  • --help — Print usage summary.
  • --verbose — Verbose module output. She'll tell you everything. Talkative queen.
  • --quiet — Quiet module output. The opposite. Silence. 🤫
  • --ui — Force launching GUI dialog. Point and click era. ✨

🌸 Parameters: the actual settings 🌸

  • input=basename [required] — Base name of input raster bands. Example: 'B.' for B.1, B.2, ... 🍓
  • output=name [required] — Name for output raster map. Name your baby. 👑
  • 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).

ngl that stray closing paren is in the original and I'm keeping it. She's iconic, she stays. 💖

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. (Literally the whole bit: cloud = cold, ground = warm, easy.) The algorithm was designed for Landsat-7 ETM+ but because reflectance is used it is also useful for Landsat-4/5 TM. Slay, backwards compatibility. 💅

🌟 NOTES 🌟

i.landsat.acca works in the current region settings. That's it. That's the note. Respect the region bestie. 🫶

⭐ 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

look at her go. two lines. one very cloud-free raster. 😭✨

🧚 REFERENCES 🧚

  • 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.
  • 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.

💜 SEE ALSO 💜

i.atcorr, i.landsat.toar — the friend group. iykyk. 🫶

👑 AUTHOR 👑

E. Jorge Tizado (ej.tizado unileon es), Dept. Biodiversity and Environmental Management, University of León, Spain. We stan. 🌈

💻 SOURCE CODE 💻

Available at: i.landsat.acca source code (history)

Accessed: Saturday Jan 17 05:41:41 2026

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© 2003-2025 GRASS Development Team, GRASS GIS 8.4.2 Reference Manual

and that's the whole page bestie, GRASS 8.4.2 era, accessed Saturday Jan 17 05:41:41 2026, © 2003-2025 GRASS Development Team — go detect some clouds, you're gonna eat 💅✨🎀

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