i.emissivity(1grass) GRASS GIS User's Manual i.emissivity(1grass)
NAME
i.emissivity - Computes emissivity from NDVI, generic method for
sparse land.
KEYWORDS
imagery, emissivity, land flux, energy balance
SYNOPSIS
i.emissivity
i.emissivity --help
i.emissivity input=name output=name [--overwrite] [--help] [--ver-
bose] [--quiet] [--ui]
Flags:
--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 [required]
Name of the NDVI map [-]
output=name [required]
Name of the output emissivity layer
DESCRIPTION
i.emissivity calculates the emissivity in the longwave radiation spec-
trum, 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 (Basti-
aanssen, 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 interac-
tion. 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.
SEE ALSO
i.eb.netrad
REFERENCES
• Bastiaanssen, W.G.M., 1995. Estimation of Land surface parame-
ters 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 emis-
sivity 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 mea-
surements of several soils and vegetation types in the 8-14 µm
wave band: Analysis of two field methods. Remote Sensing of En-
vironment 59(3): 490-521.
AUTHOR
Yann Chemin, GRASS Development Team
SOURCE CODE
Available at: i.emissivity source code (history)
Accessed: unknown
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