| Navigator 
Keyboard, Color 
Track Ball Display 
Ship-Borne Computer 
Rate Gyro Determination 
of Position Control 
Engine 
Speed-Log.: #77 a Nan aitu À dal caen ave 05 
oi bu n soit 
| Electronic ! ! Traffic ! ! Dynamic ! 
GPS- I Chart | ! "Rules ^|. T ! Models | 
Receiver bci TOWN COCA LORS 
  
  
  
Figure 1: Configuration of the integrated navigation system 
imum speed. A /aser scanner will be used to enable 
automatic entering into locks and navigation in very 
narrow canals. The accuracy obtainable with a stan- 
dard radar is not sufficient for this purpose. Among 
the non-imaging sensors, the gyroscope gives a mea- 
surement for the heading angle respectively for the 
turning rate of the vessel. The speed-log renders 
measurements of the speed over ground or relative 
to the water. The main output of the GPS-receiver 
consists of positional coordinates, based on an abso- 
lute coordinate system. It can also supply the speed 
over ground. 
On the right side of figure 1, the actuators are 
shown. During an automatic cruise, the computer 
can control the engine throttle and the rudder of the 
vessel. 
In the center of the figure, the navigation system is 
represented with all its tasks in the ship-borne com- 
puter. The computing hardware is a standard DEC- 
MicroVAX under the VAXELN real-time operating sys- 
tem. The first task, symbolized by an ellipse, is the 
determination of the position of the vessel. For this 
purpose, all the signals of the various sensors are 
combined in order to obtain the position and heading 
of the vessel. The matching of the radar image to 
the electronic chart, as explained in section 4, is a 
peculiar feature of this system. 
The radar image is also utilized for the determina- 
64 
tion of the traffic situation. The trajectories of other 
vessels are tracked over sequences of radar images. 
Principally, every echo in the radar image located 
in the waterway can stem from a foreign vessel. A 
multiple-target tracking algorithm results in estimates 
for the position, speed and heading of these vessels. 
The results of the determination of the position and 
the traffic situation are fed into the third task of the 
navigation system, the guidance of the vessel. The 
trajectory planned for the vessel is input to the control 
task. This task acts on the rudder and engine throttle 
of the vessel. 
The integrated navigation system is supervised by 
the human navigator of the vessel. The results of the 
different tasks are presented on a color display. The 
navigator can interact with the system by means of a 
track ball and a keyboard, supplementing or overrid- 
ing the results of the guidance task. 
A major resource for all the tasks of the integrated 
navigation systemis the a-priori knowledge deposited 
in knowledge bases within the computer. These 
knowledge bases are displayed as dashed boxes in 
figure 1. They consist of a database for the electronic 
chart, traffic rules and dynamic models for the own 
craft and for other vessels. The knowledge bases 
contain most of the information the navigator himself 
has to possess for navigation purposes. For exam- 
ple, the electronic chart supplies the route knowledge 
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