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4.2.2.1.4 Plan track 
From the data type “Ship data”, it is primarily the dimensions of the ship (length, width, draught) which 
are required for track planning. Furthermore, this datum contains information on the sensor technology 
available to execute the voyage plan (particularly the accuracy of the sensors used). In general it should 
be borne in mind that not all elements of a composite data type are necessarily used by the particular 
process. 
In the process “Stipulating the track limits” (DFD 1.1.4.2), it is possible to distinguish two sub-areas de 
limited in relation to one another. The result of the process “Determine maximum transverse deviations” 
(1.1.4.2.1) constitutes the limits which are taken into account within the frame of course control (i.e. 
‘Track control”). The maximum longitudinal deviation (1.1.4.2.2) primarily serves as a limit for control 
ling speed. 
As becomes clear on comparing DFD 1.1.4.3 with DFD 1.1.3, it is also necessary to make a distinction 
in the case of the way point list between a “track way point list” and a “route way point list” - in analogous 
manner to distinguishing the states “route" and “track” in the voyage plan data. The process 1.1.4.3.1 
“Stipulate track way point list" comprises the functions “generate, modify and delete way points of a 
track”. The stipulation of the rudder setting points (process 1.1.4.3.3) likewise comprises the determina 
tion of early warning positions “Wheel over lines”, “Forwarding distances”) before reaching the rudder 
setting point. For the purposes of this, appropriate early warning times and distances must be taken 
into account. 
When considering DFD 1.1.4.4 it should be borne in mind that the maximum rudder position determined 
here actually represents a physical limitation of the maximum rudder angle to the value set here. This 
value is generally set in fixed manner in the auto pilot by the user. Only by manual control it is possible 
to exceed this value. In contrast to this, the limit value ROT/turning radius does not represent a “true” 
physical limitation, as a result of the inertia of the ship system. The controller will instead trim when the 
value is exceeded. At present, there is freedom of choice with regard to determination of the transition 
behaviour at course changing points. In principle, both control via the turning behaviour (ROT) and also 
position-assisted control via the turning radius to be followed are conceivable. As a rule, the user also 
has both alternatives available in track planning. Internally, control is generally effected by means of the 
ROT, since errors in the position determination processes (eg static fluctuations when using GPS) may 
have serious consequences on the behaviour of the ship in the event of changes in course. There are 
however highly accurate track control systems with radius control in the course of development. The 
current value for ROT considered by the auto pilot is mostly calculated internally - even when it is avail 
able in the system. 
With regard to the correction information flowing into the planning process, it should be noted that this 
must relate to the current voyage plan data. In the event of simultaneous modification of way points and 
other voyage plan data (eg manoeuvring limits), care should therefore be taken to ensure consistency.