1i.emissivity(1)             GRASS GIS User's Manual            i.emissivity(1)
2
3
4

NAME

6       i.emissivity   -  Computes  emissivity  from  NDVI,  generic method for
7       sparse land.
8

KEYWORDS

10       imagery, emissivity, land flux, energy balance
11

SYNOPSIS

13       i.emissivity
14       i.emissivity --help
15       i.emissivity input=name output=name  [--overwrite]   [--help]   [--ver‐
16       bose]  [--quiet]  [--ui]
17
18   Flags:
19       --overwrite
20           Allow output files to overwrite existing files
21
22       --help
23           Print usage summary
24
25       --verbose
26           Verbose module output
27
28       --quiet
29           Quiet module output
30
31       --ui
32           Force launching GUI dialog
33
34   Parameters:
35       input=name [required]
36           Name of the NDVI map [-]
37
38       output=name [required]
39           Name of the output emissivity layer
40

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).
46
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).
50
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.
58

REFERENCES

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

SEE ALSO

75        i.eb.netrad
76

AUTHOR

78       Yann Chemin, GRASS Development Team
79

SOURCE CODE

81       Available at: i.emissivity source code (history)
82
83       Accessed: Mon Jun 20 16:47:28 2022
84
85       Main index | Imagery index | Topics index | Keywords index |  Graphical
86       index | Full index
87
88       © 2003-2022 GRASS Development Team, GRASS GIS 8.2.0 Reference Manual
89
90
91
92GRASS 8.2.0                                                    i.emissivity(1)
Impressum