138 
Table 1. Locations and vegetation types of Hapex Sahel study sites selected in this study. 
Station_name 
Latitude 
Longitude 
Location 
Millet Site - H2SIS Team 
13.538833 
2.513917 
Central West 
Fallow site - H2SIS Team 
13.542333 
2.513333 
Central West 
Degraded Fallow site - H2SIS Team 
13.553167 
2.568 
Central West 
Tiger Bush Site - H2SIS Team 
13.502167 
2.578667 
Central West 
Day of Year Day of Year 
Figure 1. Temporal Red (dotted line) and NIR (solid) reflectance profiles and corresponding NDVI 
(solid with dots) for Fallow (a), Degraded Fallow (b). Millet (c), and Tiger Bush (d) study sites. 
Comparison of Different Algorithms 
The AVG, Min View are compared with the MVC, Min Chi, and Max CH4 because of the similarities in the numbers 
of retained pixels, and the SW was compared with the BISE because of their similarities in the following analysis. 
The AVG, Min View, Min Chi, and Max Ch4 are compared with the MVC algorithm in Figure 2 for the four 
study sites, with the NDVI as the classifier. In general, the composited results of the four algorithms are similar in 
temporal variations and in that they showed some variations among the study sites. For the Tiger Bush site, there are 
little differences among these algorithms, while for Millet and Degraded Fallow sites the AVG resulted in a lower 
profiles than other algorithms. The similar results from different compositing algorithms may have been due to several 
reasons. First, although the pixel selection criteria (highest NDVI, minimal view, maximum Channel 4, or minimum 
Channel 1) were different, they all corresponded the same condition where NDVI is ma ximum . Second, the choice of 
pixels within each compositing period is limited by the available number of candidate pixels. In some periods, there 
was only one or two 
selected by these alg 
unable to pick anom: 
for AVG. resulted ii 
The results 
profiles in Figure 3 f 
and the solid lines 
variations of the ND 
both SW and BISE i 
The BISE resulted it 
apparently due to tfa 
and Tiger Bush site: 
can be described as 
not result in sharp a 
the BISE, but neve: 
Both the S\ 
by external factors 1 
SW and the BISE te 
Some compositing j 
pixels limited the ch 
from the lack of dat 
This shortcoming a 
However, increasing 
0.4 
0.35 
Fallow Site 
0.1 
120 140 160 
Figure 2. 
line), Mh 
(a) Falloi