om 
Figure 2. Radar map over Singó. 
Text information contains Date, Time, Aircraft position (top left 
corner), Aircraft heading (degrees), Coast Guard region, Serial num- 
ber and picture number. The horizontal bar at the top of the screen 
is a readout of the 64 discrete grey levelsof the digitalized picture. 
An oil spill makes the sea surface considerably smoother 
than the surface of the surrounding unpolluted water. The 
smooth surface gives less radar backscatter and the oil 
slick will appear as a dark area on the radar image. Figure 
3 shows some oil spills recorded in June 1978 in the Baltic 
Sea. 
Various types of ice give different radar backscatter as 
shown by Figure 4. As a general rule a rough surface gives 
a strong reflected signal and appears white on the picture 
while level ice turns up black. Classification of ice can 
however, not be made from greytones only. One also has to 
consider geometrical forms and surface textures.