Skip to content

i.emissivity

Computes emissivity from NDVI, generic method for sparse land.

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

Example:

i.emissivity input=name output=name

grass.script.run_command("i.emissivity", input, output, overwrite=False, verbose=False, quiet=False, superquiet=False)

Example:

gs.run_command("i.emissivity", input="name", output="name")

Parameters

input=name [required]
    Name of the NDVI map [-]
output=name [required]
    Name of the output emissivity layer
--overwrite
    Allow output files to overwrite existing files
--help
    Print usage summary
--verbose
    Verbose module output
--quiet
    Quiet module output
--qq
    Very quiet module output
--ui
    Force launching GUI dialog

input : str, required
    Name of the NDVI map [-]
    Used as: input, raster, name
output : str, required
    Name of the output emissivity layer
    Used as: output, raster, name
overwrite: bool, optional
    Allow output files to overwrite existing files
    Default: False
verbose: bool, optional
    Verbose module output
    Default: False
quiet: bool, optional
    Quiet module output
    Default: False
superquiet: bool, optional
    Very quiet module output
    Default: False

DESCRIPTION

i.emissivity calculates the emissivity in the longwave radiation spectrum, according to the semi-empirical equation related to NDVI by Caselles et al. (1997), 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).

The emissivity is 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.

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)
Latest change: Thursday Feb 27 06:04:10 2025 in commit 0ecd9fd