But it is not the aim of this paper to extoll the virtues of a cloud 
penetration capability. That was established in 1965. Rather, it will be 
demonstrated that through radar-imaging data can be generated and presented 
in such a way that the cloud penetration capability becomes the icing on the 
cake. In addition, through the utilization of both sensor products, those 
of SLAR and LANDSAT's MSS, the maximum amount of terrain and cover data will 
be revealed. 
Each system provides unique data: the LANDSAT MSS sensing that which is 
seen by the human eye and extending into the optically recorded near-infrared 
range of the spectrum and the SLAR sensing target roughness and dielectric 
properties in the microwave portion of the electromagnetic spectrum. The 
latter presents the capability of discrimination between objects on the basis 
of other than spectral contrast which is the limitation in the optical region. 
For example, in flat heavily-vegetated terrain in northern Louisiana, the 
stream valleys and adjacent swamps are occupied by a mix of deciduous and 
pine trees whereas the interfluve areas are dominated by pines (Dellwig and 
Bare, in press). The vegetation of the stream valleys provides a high return 
in contrast with the low return of the interfluve areas, primarily because of 
the strong contrast in leaf configuration. 
The capability of providing unique data is not solely a function of a 
unique spectral response. Commercial imaging-radars achieve a degree of 
spatial resolution several factors better than that of the LANDSAT MSS. More 
important, however, is the generation of shadows by a side-looking radar, 
particularly in areas of low relief. At minimum depression angles, for example, 
a shadow length may be as much as ten times the height of the object (Table 1) 
Table 1 
Shadow Length on Flat Terrain of Objects at 5?, 10? and 15? Depression Angles 
Height of Length of Shadow Length of Shadow Length of Shadow 
Object at 5? Depression at 10? Depression at 15? Depression 
in Feet Angle in Feet Angle in Feet Angle in Feet 
2 22.86 11.34 7.47 
10 114.30 56.72 37.33 
50 571.49 283.61 186.64 
Shadowing of faults and fractures across which relief has developed through 
movement or erosion accentuates minimal surface relief and increases the 
capability for detection of such features. Obviously, however, low depression 
angles are not advantageous in high relief terrain. They can be reduced with 
a change in aircraft elevation or by moving into the near range of the image 
(Table 2). Consequently, overlapping adjacent flight lines of approximately 
Table 2 
Depression Angles with 25 Kilometer Swathwidth and Zero Delay 
Altitude Near R Far R Mid-R SW Used 
20,000' (6098m) 31° 10° 22° 
12,000' (3658m) 20° 6° 14° 
8,000' (2434m) 14° 4° 9° 
      
    
      
   
  
    
    
    
   
   
   
    
    
     
    
   
    
     
     
         
    
     
   
   
   
    
    
   
     
   
   
60% essen 
position 
desirable 
a single 
the evalu 
Took from 
1969). 
Exem 
return is 
The river 
Streams s 
the LANDS 
bodies cr 
contrast 
cent sava 
even negl 
height co 
case in a 
is a func 
transmiss 
energy re 
aspect an 
near rang 
accentuat 
to the lo 
The 
tion mapp 
leaf meso 
red refle 
propertie 
tion. In 
fication