i.emissivity(1grass)

1i.emissivity(1)               Grass User's Manual              i.emissivity(1)
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NAME

6       i.emissivity   -  Computes  emissivity  from  NDVI,  generic method for
7       sparse land.
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KEYWORDS

10       imagery, emissivity, land flux, energy balance
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SYNOPSIS

13       i.emissivity
14       i.emissivity --help
15       i.emissivity input=name output=name  [--overwrite]   [--help]   [--ver‐
16       bose]  [--quiet]  [--ui]
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18   Flags:
19       --overwrite
20           Allow output files to overwrite existing files
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22       --help
23           Print usage summary
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25       --verbose
26           Verbose module output
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28       --quiet
29           Quiet module output
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31       --ui
32           Force launching GUI dialog
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34   Parameters:
35       input=name [required]
36           Name of the NDVI map [-]
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38       output=name [required]
39           Name of the output emissivity layer
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DESCRIPTION

42       i.emissivity  calculates the emissivity in the longwave radiation spec‐
43       trum, according to the  semi-empirical  equation  related  to  NDVI  by
44       Caselles et al. (1997), valid in the NDVI range of 0.16 to 0.74 (Basti‐
45       aanssen, 1995).
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47       Caselles et al. (1997) give reference (in Table 3 and Figure 2) to both
48       the  NDVI  range  used  (0.15  - 0.71) and the corresponding emissivity
49       range used (0.97 - 0.99).
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51       The emissivity is the efficiency of longwave energy  returning  to  the
52       atmosphere  from  the skin surface. The skin surface receives heat from
53       the thermal infrared radiation of the Sun, through atmospheric interac‐
54       tion.  A part is returned to the atmosphere fastly, and another part is
55       kept in the surface skin to  be  returned  later.  In  more  scientific
56       terms,  the  grey  body  radiation is equal to the black body radiation
57       times the emissivity.
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REFERENCES

63           ·   Bastiaanssen, W.G.M., 1995.  Estimation of Land surface parame‐
64               ters  by remote sensing under clear-sky conditions. PhD thesis,
65               Wageningen University, Wageningen, The Netherlands.  (PDF)
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67           ·   Caselles, V., C. Coll, and E. Valor, 1997.  Land surface  emis‐
68               sivity  and  temperature determination in the whole HAPEX-Sahel
69               area from AVHRR data. International Journal of  Remote  Sensing
70               18(5):1009-1027.
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72           ·   Rubio,  E., V. Caselles, and C. Badenas, 1997.  Emissivity mea‐
73               surements of several soils and vegetation types in the 8-14  µm
74               wave  band:  Analysis  of  two field methods. Remote Sensing of
75               Environment 59(3): 490-521.
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AUTHOR

78       Yann Chemin, GRASS Development Team
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80       Last changed: $Date: 2016-06-06 23:50:02 +0200 (Mon, 06 Jun 2016) $
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SOURCE CODE

83       Available at: i.emissivity source code (history)
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85       Main index | Imagery index | Topics index | Keywords index |  Graphical
86       index | Full index
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88       © 2003-2019 GRASS Development Team, GRASS GIS 7.6.0 Reference Manual
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92GRASS 7.6.0                                                    i.emissivity(1)