The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008
(c) original Aqua image
Figure 4. Mean column power spectrums of the original and destriped MODIS images.
Figure 3 shows the mean cross-track profiles of the original
images and the destriped results using the proposed algorithm.
It can be seen that the rapid fluctuations in the original data are
strongly reduced in the destriped images. The mean column
power spectrums of the original and destriped images are
shown in
Figure 4. For better visualization of noise reduction, very high
spectral magnitudes are not plotted. It is easily recognized that
the value of the power spectrum of the frequency components
where the pulses exist has been strongly reduced in the
destriped images.
The inverse coefficient of variation (ICV) and ratio of noise
reduction (NR) are employed to take the quantitative analysis.
The ICV index (Nichol and Vohora, 2004; Rakwatin et al.,
2007; Smith and Curran, 2000) is defined as
ICV = -^_ (17)
K d
where R a is the signal response of a homogeneous image region
and is calculated by averaging the pixels within a window of a
given size; R sd refers to the noise components estimated by
calculating the standard deviation of the pixel. In our
experiments, we selected two 10x10 homogeneous regions for
the ICV evaluation. The NR index (Chen et al., 2003;
Rakwatin et al., 2007) is used to evaluate the image in the
frequency domain. It is defined by
NR=— (18)
where N 0 is the power of the frequency components produced
by stripes in the original image, and V, stands for that in the
destriped image. N 0 and V, can be calculated by
N, = ^P,(D) (19)
P
where PfD) is the averaged power spectrum down the columns
of an image with D being the distance from the origin in
Fourier space, and p is the stripe noise region of the spectrum.
The ICV and NR evaluation results are, respectively, shown in
Table 1 and
Table 2. The proposed algorithm always obtains the best results
in the several destriping methods (Butterworth filtering,
moment matching and histogram matching).
Original
Butterworth
Moment
Histogram
Proposed
Terra
Sample 1
24.08
27.26
39.32
43.93
46.79
Band 28
Sample2
17.27
23.93
21.82
21.49
25.87
Aqua
Sample 1
7.94
14.49
24.42
22.72
26.83
Band 30
Sample2
9.66
15.74
21.03
24.86
30.31
Table 1. ICVs of the original and destriped MODIS data
Original
Butterworth
Moment
Histogram
Proposed
Terra Band 28
1.00
4.39
15.96
17.71
25.81
Aqua Band 30
1.00
4.26
4.82
5.05
7.56
Table 2. NRs of the original and destriped MODIS data
67