User's Manual

Table Of Contents
ED 3100 G 140 / 04 (2011-11)
Operating Instructions
III-3 Permanent Area for Navigation
III Main Applications.fm / 10.11.11
III-49
NACOS Platinum
3.3 Vector and Trails
Basically, the display of vectors and trails depends on the way
of speed determination within the system.
Speed Over Ground (SOG), the so-called Bottom-Track, or
Speed Through Water (STW), the so-called Water-Track can
be used in order to compute the vectors for the own ship and
the targets.
The speed vectors of the own ship and of targets, the trails of
targets, the past-position plot and the path prediction for the
own-ship can be configured here.
The speed vector, the target trails and the target´s past posi-
tion plot can be displayed as true or relative.
The own ship´s position plot is only displayed as true plot, i.e. it is independent of the T/REL setting.
The setting T for true or REL for relative measurements is valid for all vectors and trails within all
navigational applications of an MFD.
As mentioned before, the calculation principles for relative or true data have some important differences:
The relative data are calculated directly by the ARPA. The ARPA uses the plots of consecutive antenna
scans in order to calculate relative course and speed of the target. Out of this, CPA and TCPA can be
calculated.
In order to calculate true data of a target, the own ship´s course and speed must be known. The accu-
racy of the true data calculation depends on the accuracy of the sensors from which the own ship´s
course and speed are provided.
If there is any doubt that the own ship´s speed data are not correct, use the REL
target data and PPI presentation for collision avoidance purposes!