- XXIII - 
Sea state 
Status of the sea condition due to the weather environment, expressed as 
a sea state 0 for flat conditions with minimal wind, to sea state 8 for 
very rough sea conditions. 
 
 
SET 
The current direction for manual correction or the current speed on the 
horizontal axis of the 2-axis log is displayed. 
 
 
Sleeping AIS target 
A target indicating the presence and orientation of a vessel equipped 
with AIS in a certain location. 
 
 
SOG 
Speed Over the Ground 
The speed of the ship relative to the earth, measured on board of the 
ship. 
SP 
Short Pulse 
 
 
STAB 
STABilization 
 
 
STW 
Speed Through Water 
The speed of the ship relative to the water surface. 
T 
TCPA 
Time to Closest Point of Approach to own ship 
 
 
Test target 
Radar target of known characteristics used for test requirement 
 
 
TM 
True Motion 
A display across which own ship moves with its own true motion. 
 
 
Trails 
Tracks displayed by the radar echoes of targets in the form of an 
afterglow. 
 
 
Trial maneuver 
A graphical simulation facility used to assist the operator to perform a 
proposed maneuver for navigation and collision avoidance purposes. 
 
 
True course 
The direction of motion relative to ground or to sea, of a target 
expressed as an angular displacement from north 
 
 
True speed 
The speed of a target relative to ground, or to sea 
 
 
True vector 
A vector representing the predicted true motion of a target, showing 
course and speed with reference to the ground or sea 
 
 
 
TT 
Target Tracking. 
A computer process of observing the sequential changes in the position 
of a radar target in order to establish its motion.    Such a target is a 
Tracked Target.