i.aster.toar(1grass)

✨ i.aster.toar ✨

okay bestie, welcome to the i.aster.toar page from the GRASS User's Manual (that's the <rainbow>1grass</rainbow> section, iykyk) 💖

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🌸 NAME 🌸

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

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🎀 KEYWORDS 🎀

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

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🦋 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]

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🌈 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

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🫶 Parameters 🫶

• input=name[,name,...] [required] — Names of ASTER DN layers (15 layers). all fifteen, bestie, don't leave any of them at home 😭
• 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) 🎁

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💖 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. she's giving radiometric glow-up ✨. it's 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, in that order, periodt 💅

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🧚 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. and this is the whole vibe of it:

/*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)*/

like, read the comments, they're doing so much heavy lifting 💀

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🍓 SEE ALSO 🍓

• i.landsat.toar
• r.in.aster
• ASTER sensor data download: ASTER: Advanced Spaceborne Thermal Emission and Reflection Radiometer

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👑 AUTHOR 👑

Yann Chemin, CSU, Australia 🌏 — icon behavior, honestly

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💜 SOURCE CODE 💜

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

Latest change: Saturday May 31 03:33:38 2025 in commit: 193579448e84c26e98f04e97918b6c61d5a2adff

Main index | Imagery index | Topics index | Keywords index | Graphical index | Full index

© 2003-2026 GRASS Development Team, GRASS 8.5.0 Reference Manual

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and that's the whole page, bestie 🫶 she's from GRASS 8.5.0, last touched Saturday May 31 03:33:38 2025, and the copyright holds it down from 2003-2026 with the GRASS Development Team — mwah, go run her 💅🌸✨