EM 1110-2-2907
1 October 2003
(1) Information pertaining to the minimum and maximum brightness (Lmin and Lmax
respectively) is usually found in the metadata (see Chapter 5). The equation for deter-
mining radiance from the digital number is:
L = (Lmax Lmin)/255 DN + Lmin
(2-10)
where
radiance expressed in Wm-2 sr-1
L
=
=
spectral radiance corresponding to the minimum digital number
Lmin
Lmax
=
spectral radiance corresponding to the maximum digital number
DN
=
digital number given a value based on the bit scale used.
(2) This conversion can also be used to enhance the visual appearance of an image
by reassigning the DN values so they span the full gray scale range (see Paragraph 5-20).
i. Spectral Bands.
(1) Sensors collect wavelength data in bands. A number or a letter is typically as-
signed to a band. For instance, radiation that spans 0.45 to 0.52 m is designated as band
the L-band. Not all bands are created equally. Landsat band 1 (B1) does not represent the
same wavelengths as SPOT's B1.
(2) Band numbers are not the same as sensor numbers. For instance Landsat 4 does
not refer to band 4. It instead refers to the fourth satellite sensor placed into orbit by the
Landsat program. This can be confusing, as each satellite program has a fleet of satellites
(in or out of commission at different times), and each satellite program will define bands
differently. Two different satellites from the same program may even be collecting radia-
tion at a slightly difference wavelength range for the same band (Table 2-6). It is, there-
fore, important to know which satellite program and which sensor collected the data.
Table 2-6
Landsat Satellites and Sensors
The following table lists Landsat satellites 1-7, and provides band information and pixel size. The band
numbers for one sensor does not necessarily imply the same wavelength range. For example, notice that
band 4 in Landsat 1-2 and 3 differ from the band 4 in Landsat 4-5 and Landsat 7. Source:
Satellite
Sensor
Band number
Band wavelengths
Pixel Size
Landsats 1-2
RBV
1)
0.45 to 0.57
80
2)
0.58 to 0.68
80
3)
0.70 to 0.83
80
MSS
4)
0.5 to 0.6
79
5)
0.6 to 0.7
79
6)
0.7 to 0.8
79
7)
0.8 to 1.1
79
Landsat 3
RBV
1)
0.45 to 0.52
40
2-35
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