The obstacle data used by the VGS is provided by the object
detection module. This module analyzes the data from the
scanning sonar and extracts lines which can be seen in Fig. 10.
The VGS internal representations of these walls are lines. It
is easier and more effective to use lines in the vehicle control
algorithms than the unprocessed sonar image representation.
The lines are represented as contact points on the detected
walls, which are the nearest point on the wall according to the
vehicle. This point PW is described by the distance db to the
current vehicle position PV and the north bearing angle αb seen
from the vehicle. Fig. 11 illustrates this description. Additionally
to this minimal wall description, the geodetic coordinates are also
delivered.