rtues of a cloud 
ather, it will be 
ated and presented 
es the icing on the 
r products, those 
and cover data will 
ensing that which is 
corded near-infrared 
ss and dielectric 
c spectrum. The 
objects on the basis 
n the optical region. 
n Louisiana, the 
of deciduous and 
pines (Dellwig and 
ovides a high return 
primarily because of 
y a function of a 
eve a degree of 
e LANDSAT MSS. More 
e-looking radar, 
on angles, for example, 
the object (Table 1). 
] 15? Depression Angles 
Length of Shadow 
at 15? Depression 
Angle in Feet 
7.47 
37.33 
186.64 
developed through 
| increases the 
rever, low depression 
can be reduced with 
range of the image 
's of approximately 
| Zero Delay 
Mid-R SW Used 
22? 
14° 
9° 
60% essentially assures the placement of any terrain feature in a near optimum 
position for examination. Particularly valuable in high relief terrain but 
desirable under all conditions in all terrains are opposing "looks". Although 
a single look may provide most of the desired data, it was demonstrated during 
the evaluation of imagery from Darien Province, Panama, that each additional 
look from a different direction provided some additional information (MacDonald, 
1969). 
Drainage Network 
Exemplifying the value of shadowing combined with contrasts in signal 
return is an area southwest of Atakpamé, Togo, West Africa (Figure 2a, b, c). 
The riverain forest with tree heights up to 120 feet spans all orders of 
streams shown in the image. Because the channels are completely obscured, 
the LANDSAT Band 7 image which would normally be expected to present the water 
bodies characteristically black, records the network only on the basis of a 
contrast in response of vegetation occupying the valley with that of the adja- 
cent savanna and fails to reveal lower order streams. On the radar image, 
even neglecting contrast in canopy configuration and dielectric properties, 
height contrast in itself is sufficient for valley accentuation. As is the 
case in any reflective surface, the amount of energy returned to the source 
is a function of the orientation of the surface relative to the direction of 
transmission (aspect angle). Thus with the aspect angle of the transmitted 
energy relative to the riverain forest essentially 90° in contrast with the 
aspect angle, with flat savanna (less than 45°) a brightness contrast on the 
near range side (Figure 3) is assured. This is emphasized by the greater 
accentuation of higher order streams when oriented normal rather than parallel 
to the look direction. 
Vegetation 
The value of using imagery of both sensors is best emphasized in vegeta- 
tion mapping. On Band 7 LANDSAT imagery, vegetation contrasts are related to 
leaf mesophyll structure, including water content, and on Band 5 to visible 
red reflectivity. Contrasts on radar imagery are dependent upon dielectric 
properties, strongly influenced by moisture content and stem and leaf configura- 
tion. In Togo, in general, a region of flat to gently rolling terrain classi- 
fication of 10 distinct vegetation categories has been realized (Table 3). 
Table 3 
Vegetation Types Detectable on X-Band Radar Imagery 
from Togo, West Africa 
Semideciduous forest 
Deciduous woodland 
Savanna 
Seasonally inundated grassland 
Marshes and swamps 
Cultivated vegetation: 
a. Oil palms 
b. Coconut palms 
C.. Teak 
d. Intensive mixed agriculture (corn, millet, cassava, 
rice, yams, bananas, plantain, beans, and cotton) 
e. Eucalyptus 
O C BE C9 n9 —