5─5 
 
 
 
 
Fig. 5-3    Relative Vector and True vector 
 
 
 
Radar and Collision Avoidance 
 
Radar is still playing an important roll for collision prevention and positioning.    A plotter is used to further 
enhance the radar functionality.  The plotter is capable of plotting other positions of other ships in 3 to 6 
minute intervals to monitor their movement.    The plots of other ships represent their tracks relative to own 
ship, and it is shown whether there is a risk of collision, namely CPA and TCPA can be obtained.    This method 
using a plotter is fairly effective, but the number of target ship, which are manually plotted, is limited and it 
takes several minutes to measure those.