i.aster.toar(1)

📦
version 8.4.2 · 8 versions
, in fedora 44

💫 i.aster.toar 💫

okay bestie, welcome to i.aster.toar(1) — your fave lil GRASS GIS User's Manual glow-up 💖

✨ NAME ✨

i.aster.toar — Calculates Top of Atmosphere Radiance/Reflectance/Brightness Temperature from ASTER DN. no cap, that's the whole job 💅

🎀 KEYWORDS 🎀

imagery, radiometric conversion, radiance, reflectance, brightness temperature, satellite, ASTER

🌈 SYNOPSIS 🌈

i.aster.toar
i.aster.toar --help
i.aster.toar [-rabcde] input=name[,name,...] dayofyear=float
sun_elevation=float output=name  [--overwrite]  [--help]  [--verbose]
[--quiet]  [--ui]

🦋 Flags 🦋

  • -r — Output is radiance (W/m2)
  • -a — VNIR is High Gain
  • -b — SWIR is High Gain
  • -c — VNIR is Low Gain 1
  • -d — SWIR is Low Gain 1
  • -e — SWIR is Low Gain 2
  • --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=name[,name,...] [required] — Names of ASTER DN layers (15 layers)
  • dayofyear=float [required] — Day of Year of satellite overpass [0-366]
  • sun_elevation=float [required] — Sun elevation angle (degrees, < 90.0)
  • output=name [required] — Base name of the output layers (will add .x)

💜 DESCRIPTION 💜

so i.aster.toar calculates the Top Of Atmosphere (TOA) reflectance for Terra-ASTER L1B in the visible, NIR and SWIR bands (9+1 bands) and brightness temperature for the TIR bands (5 bands), all from L1B DN values. it's giving glow-up for your raw satellite data ✨ It is useful to apply after import of original ASTER imagery that is generally in standard DN values range.

The order of input bands is

  • VNIR: 1,2,3N,3B
  • SWIR: 4,5,6,7,8,9
  • TIR: 10,11,12,13,14

in one comma-separated list. 🫶 one list, all the bands, so organized, we love to see it.

🔥 NOTES 🔥

Internally, a gain code is defined to modify gains according to spectral bands following the GeoSystems GmbH ATCOR Ver. 2.0 Calibration Files. The function is defined in gain_aster.c file.

/*Gain Code*/
    /*0 - High (Not Applicable for band 10-14: TIR)*/
    /*1 - Normal*/
    /*2 - Low 1(Not Applicable for band 10-14: TIR)*/
    /*3 - Low 2(Not Applicable for Band 1-3N/B and 10-14)*/
👑 gain codes live in gain_aster.c and they do NOT all apply to every band — read the comments, bestie, they're doing the most for a reason.

🌟 SEE ALSO 🌟

  • i.landsat.toar, r.in.aster

ASTER sensor data download: ASTER: Advanced Spaceborne Thermal Emission and Reflection Radiometer 🛰️

👑 AUTHOR 👑

Yann Chemin, CSU, Australia

🧚 SOURCE CODE 🧚

Available at: i.aster.toar source code (history)

Accessed: Saturday Jan 17 05:41:38 2026

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