680 
Figure 7: Reflectance image over snow/ice 
at 450 nm. 
Figures 8 and 9 show the bidimensional and spectral characteristics of the targets. For the 
viewing angles of 15 and 30 degrees selected, the polar diagrams exhibit very small 
angular effects and differences (the sun angles for the snow/ice and cloud scenes are 66° 
and 61°, respectively, making the comparison possible). 
Figure 8 Reflectance polar diagram for 
9v = l5 degrees over snow and cloud. 
Cloud 
Figure 9 Reflectance polar diagram for 
&v = 30degrees over snow and cloud. 
Regarding spectral signature (figure 6) the two objects exhibit common features, in 
particular the same decrease of the reflectance with the wavelength. The level of 
reflectance, futhermore, remains similar for snow-ice and clouds in all spectral channels 
(slightly lower for clouds), which may be explained by the thickness of the cloud layer and 
the reflectance of underlying surface. According to us the stratocumulus clouds were