i.emissivity(1)

📦
version 8.4.2 · 8 versions
, in fedora 44

💖 i.emissivity 💖

okay bestie, welcome to i.emissivity(1) from the GRASS GIS User's Manual — it's giving imagery, it's giving emissivity, it's giving land flux, and honestly? it's giving energy balance too. periodt. 🦋

✨ NAME ✨

i.emissivity — computes emissivity from NDVI, a generic method for sparse land. yes bestie, that's the whole vibe. 💅

🌸 KEYWORDS 🌸

imagery, emissivity, land flux, energy balance

🎀 SYNOPSIS 🎀

i.emissivity
i.emissivity --help
i.emissivity input=name output=name  [--overwrite]  [--help]
[--verbose]  [--quiet]  [--ui]

🫶 Flags 🫶

  • --overwrite — lets your output files just overwrite the existing ones. no asking, no crying, no permission slip. 💀
  • --help — prints the usage summary so you can be like "wait what does this do again"
  • --verbose — verbose module output, aka the module will not stop talking (we love a chatty icon)
  • --quiet — quiet module output. the module goes mute. silence era. 🤫
  • --ui — forces the GUI dialog to launch, for when you want a lil window moment instead of terminal life

🌈 Parameters 🌈

  • input=name [required] — the name of the NDVI map [-]. required, bestie. you cannot skip this one. 🍓
  • output=name [required] — the name of the output emissivity layer. also required. also not optional. 💜

✨ DESCRIPTION ✨

so i.emissivity calculates the emissivity in the longwave radiation spectrum, using the semi-empirical equation related to NDVI by Caselles et al. (1997) — and no cap, that thing is valid in the NDVI range of 0.16 to 0.74 (Bastiaanssen, 1995). 🧚

Caselles et al. (1997) give reference (in Table 3 and Figure 2) to both the NDVI range used (0.15 - 0.71) and the corresponding emissivity range used (0.97 - 0.99). look at the range glow-up, we love consistency 💅

okay so what is emissivity? it's the efficiency of longwave energy returning to the atmosphere from the skin surface. the skin surface receives heat from the thermal infrared radiation of the Sun, through atmospheric interaction. a part is returned to the atmosphere fastly, and another part is kept in the surface skin to be returned later. in more scientific terms: the grey body radiation is equal to the black body radiation times the emissivity. main character physics fr fr. 🔥

📚 REFERENCES 📚

  • Bastiaanssen, W.G.M., 1995. Estimation of Land surface parameters by remote sensing under clear-sky conditions. PhD thesis, Wageningen University, Wageningen, The Netherlands. (PDF)
  • Caselles, V., C. Coll, and E. Valor, 1997. Land surface emissivity and temperature determination in the whole HAPEX-Sahel area from AVHRR data. International Journal of Remote Sensing 18(5):1009-1027.
  • Rubio, E., V. Caselles, and C. Badenas, 1997. Emissivity measurements of several soils and vegetation types in the 8-14 µm wave band: Analysis of two field methods. Remote Sensing of Environment 59(3): 490-521.

👀 SEE ALSO 👀

  • i.eb.netrad

👑 AUTHOR 👑

Yann Chemin, GRASS Development Team

💻 SOURCE CODE 💻

Available at: i.emissivity source code (history)

Accessed: Saturday Jan 17 05:41:40 2026

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bestie that's the whole page 💖 go compute some emissivity, you absolute icon 🫶✨

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