However, since set and drift affect heading and aspect, ground stabilised displays should be used with caution where target tracking is concerned. Sea stabilisation mode gives the navigator a better understanding about the aspect and therefore is used in collision avoidance.

What is difference between sea stabilization and ground stabilization?

There are two stabilisation modes – ground and sea. Ground stabilisation means that the display is referenced to the seabed by GNSS or through a twin-axis Doppler log. For sea stabilisation the display is referenced to the sea current that own ship is experiencing, typically based on SDME measurements.

Why is speed through water used for collision avoidance?

Speed through the water (STW) is the speed of the vessel referenced to the water in which it is navigating. In general, STW is used for radar collision avoidance to provide a more accurate indication of the target's aspect and SOG is used for navigation.