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.

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: Monday Apr 01 03:09:08 2024

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       © 2003-2024 GRASS Development Team, GRASS GIS 8.3.2 Reference Manual

GRASS 8.3.2                                                                                 i.emissivity(1grass)