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42  Data  flow  diagrams
4.2.1  Task  areas
The  DFD  shows  a  clear  division  between  “voyage  planning”  (Process  1)  and  executing  or  monitoring  the
voyage  (Process  2).  The  “current  voyage  plan”  memory  represents  the  connecting  link  between  these
two  processes.  Amongst  other  things,  this  memory  contains  the  set  track  valid  in  the  system,  which  is
usable  for  automatic  track  control.  Further  processes  are  used  for  the  procurement  and  administration
of  data  (mainly  irrespective  of  the  current  course  of  the  voyage:  Process  3  (integrated  in  the  voyage
progression:  Process  5).  Process  3  -  “Management  of  data  and  reference  parameters”  -  models  the
“Sea  chart  management’  (i.e.  the  administration  of  the  geographical  data  base  for  voyage  planning  and
execution)  and  the  recording  and  administration  of  ship  data.  The  data  flow  “State  variables”  forming
part  of  Process  3  primarily  models  the  transmission  of  the  ship's  position  for  selection  of  the  current  sea
chart.
It  should  be  borne  in  mind  that  the  whole  “integrated  navigation”  process  chiefly  supplies  two  items  of
output  information:  “Set  rudder  angle"  and  “Set  engine  data”.  The  information  flow  via  the  current  values ­
  of  rudder  angle  and  engine  data  is  effected  via  the  process  “State  identification”  and  is  thus  encapsulated ­
  in  the  data  flow  “Sensor  data”.