5). The shape, size, and orientation of the spectral triangle of West Africa changes 
constantly due to the diurnal and seasonal temperature variation. 
The hump on the right side of the triangle is due to the effect of the clouds, 
(Figure 1). Cool clouds shift the land and water pixels with the cloud influence in 
the scattergraph towards lower temperature direction. It also can be seen in 
Figure 2 that the cloud effects were minimized in the NDVI and TIR model 
because NDVI ratioing helped to remove a part of the cloud influence. 
The above observations suggest that all land cover types are associated in 
the natural environment and can form a global triangle in the two dimensional 
space of temperature and vegetation. The concept of the triangle and its changes 
through time and potential applications could be represented as follows: 
VEGETATION 
VEGETATION 
Figure 3. Global Triangle and Figure 4. Multi-Date Change Detection 
Vegetation Distribution 
VEGETATION 
Temperature 
Day Night 
Figure 5 Diurnal Changes of the 
Global Triangle 
VEGETATION 
Figure 6. Distinguish Vegetation 
from Background Soils 
In Figure 3, temperature increases from right to left on the bottom with a 
range of temperature from deep ocean to the temperature of hot desert. Vegetation