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II Current voyage plan data will get actual parameters from process 1 "voyage planning" di 
rectly before sailing on the corresponding segment of the track. This data will be stored in a 
data memory called "current voyage plan" (see DFD 1). 
III Corrections to voyage plans are supplied by Process 4 “Dealing with unplanned incidents” 
[2]. Voyage planning on the basis of these data always represents a modification of an ex 
isting voyage plan in operation. A factor triggering this modification is the occurrence of an 
incident for which allowance has not been made in the original planning. One result of this 
is that this form of voyage planning generally only considers a certain section of the voyage 
plan. 
When modifying a voyage plan, therefore, considerably more boundary conditions have to be taken into 
account than in new planning. The question should for example be examined as to what influence “lo 
cal” changes have on the “global” voyage plan (e.g. influence of changes on the original speed/time 
profile). Moreover it must be borne in mind that re-planning as a result of an incident previously impos 
sible to plan frequently serves to avert a direct hazard (e.g. in avoidance of collision or grounding). 
Modification of the voyage plan must therefore be rapidly and simply feasible in principle. On the other 
hand, the special “protection need” of the current voyage plan should be borne in mind, since any 
change basically represents an intervention in the current control process. 
2. Boundary conditions: hydrographic/meteorological/geographical data, ship data 
These involve influencing variables which have to be taken into account for reasons of safety, economic 
efficiency or ensuring observance of the set parameters. In this instance, hydrographic, meteorological 
and geographical data describe the situation in the surrounding environment expected during voyage 
plan execution, i.e. they involve “external boundary conditions”. In contrast to this, ship data contain 
“internal boundary conditions”. These describe “static variables” (e.g. dimensions) and the “dynamic 
behaviour'’ of the ship (e.g. for planning course changes). In the event of new planning, allowance must 
be made for a certain measure of planning uncertainty, particularly in connection with external boundary 
conditions (e.g. accuracy of the information available during planning, concerning the hydrographic or 
meteorological conditions to be expected). 
The tables on the following pages contain the requirements on the input information listed above. 
Requirements on the data types “geographical data” and “ship data” are dealt with in detail in Section 3.