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]  [--verbose]  [--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  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.

SEE ALSO

        i.eb.netrad

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.

AUTHOR

       Yann Chemin, GRASS Development Team

SOURCE CODE

       Available at: i.emissivity source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.8.2 Reference Manual