Landsat 8 OLI acquire land surface
information and store it as a Digital Number (DN) with a range between 0 and
255. This DN must be converted TOA reflectance values first, before being used
for identification of surface features of the earth. Reflectance is the
proportion of the radiation striking a surface to the radiation reflected off
of it. Landsat 8 OLI Digital Number can be converted to TOA reflectance values
using standard formulation used by the USGS. The formula is as follows :
ρλ' = MρQcal +
Aρ
ρλ' :
TOA reflectance
Mρ :
Band-specific multiplicative rescaling factor
Aρ :
Band-specific additive rescaling factor
Qcal : Digital number
Band-specific multiplicative
rescaling factor and additive rescaling factor can be referred from metadata
file (MTL file) of the image. For example, i use the metadata of Landsat 8 OLI
of Gunungsewu area. ID image that i use is LC81190662014235LGN00.
You can get it through earthexplorer.usgs.gov (see : How to get Landsat 8 OLI
). In the metadata file contained the following information
REFLECTANCE_MULT_BAND_1
= 2.0000E-05
REFLECTANCE_MULT_BAND_2
= 2.0000E-05
REFLECTANCE_MULT_BAND_3
= 2.0000E-05
REFLECTANCE_MULT_BAND_4
= 2.0000E-05
REFLECTANCE_MULT_BAND_5
= 2.0000E-05
REFLECTANCE_MULT_BAND_6
= 2.0000E-05
REFLECTANCE_MULT_BAND_7
= 2.0000E-05
REFLECTANCE_MULT_BAND_8
= 2.0000E-05
REFLECTANCE_MULT_BAND_9
= 2.0000E-05
REFLECTANCE_ADD_BAND_1
= -0.100000
REFLECTANCE_ADD_BAND_2
= -0.100000
REFLECTANCE_ADD_BAND_3
= -0.100000
REFLECTANCE_ADD_BAND_4
= -0.100000
REFLECTANCE_ADD_BAND_5
= -0.100000
REFLECTANCE_ADD_BAND_6
= -0.100000
REFLECTANCE_ADD_BAND_7
= -0.100000
REFLECTANCE_ADD_BAND_8
= -0.100000
REFLECTANCE_ADD_BAND_9
= -0.100000
The upper group are band-specific
multiplicative rescaling factor of each band, and others are band-specific
additive rescaling factor of each band. Subsequently apply these values in the
above formula through image processing device.
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