User's Manual

Synapsis Radar
with Nautoscan NX Pedestal
Operator Manual
4265.DOC020102
3-18
Edition July 2015
3.4.2 Collision Assessment (Surveillance)
Once the true velocities of own ship and targets are established (within one
minute of acquisition), it is valid to interpret displayed information for collision
assessment. TRUE and RELATIVE VECTORS are available to present target
velocities.
The NSC provides two additional surveillance features to aid in rapid
assessment of collisions potential in congested situations. When displaying
TRUE VECTORS, the operator may choose to display Potential Collision Points
(PCPs). The appearance of one or more of these symbols, on or near own
ship’s heading line, immediately signals collision potential. When displaying
RELATIVE VECTORS, the operator may choose to display all CPAs within the
set CPA limit, plus one mile of own ship whose TCPA is less than 30 minutes.
The appearance of one or more of these symbols near own ship’s current
position immediately signals collisions potential.
3.4.2.1 Accuracy of Collision Assessment
The position of PCP and CPA are the key parameter in collision assessment
and of vital importance. Both are calculated from knowledge of present position
and velocities of targets and own ship.
3.4.2.2 Displaying of CPAs
CPA is the Closest Point of Approach for any target vessel if both the target
vessel and own ship maintain course and speed. The calculated CPA will
match the actual CPA only if the present course and speed of the target vessel
has been maintained long enough for the target velocity filters to settle. The
ARPA specification allows up to three minutes for this purpose. The Radar
accomplishes this in one minute.
Furthermore, if own ship’s speed-log has no smoothing or delay in its readings,
the NSC will produce an accurate CPA even as own ship comes to a new
course and/or speed (target not maneuvering). CPA and TCPA are calculated
for all targets, once for each revolution of the Radar antenna (approximately
two seconds for Raytheon Radars).
CPA symbols will be displayed if:
(1) the operator selects the CPA/PCP display button on the collisions
assessment menu page and