Why speed over water is 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.

What is speed over water?

Speed over water is the distance traveled in one hour with respect to water. Similarly speed over ground is the distance traveled in one hour with respect to ground.

What is speed over ground compared with speed through water in using for collision avoidance?

Speed over ground is the speed of the ship with respect to the ground or any other fixed object such as fixed buoy or island. Speed through water is the speed of the ship with respect to the water such as anything floating on water.

What is speed in navigation?

knot, in navigation, measure of speed at sea, equal to one nautical mile per hour (approximately 1.15 statute miles per hour). Thus, a ship moving at 20 knots is traveling as fast as a land vehicle at about 23 mph (37 km/hr).

Why is it that your speed through the water is zero but your speed over the ground is for example 5 knots?

Speed Over the Ground (SOG) is the speed of the vessel relative to the surface of the earth. Speed Through Water (STW) is the speed of the vessel relative to the water. It is possible for the STW to be zero while the SOG is 5 knots, for example if the boat was drifting in a 5 knot current.

What is through speed?

To move or pass through something with great speed. To progress or proceed through something with great speed, especially in a hasty, careless, or indifferent manner. I just felt like the pastor sped through the wedding ceremony. If you speed through the material, you’re not going to remember it on the day of the exam.

What measures speed over ground?

GPS speed, meaning Speed Over Ground (SOG), is a measure of our total speed over the surface of the earth, regardless of how that speed was accomplished, whether from our own propulsion, wind, currents, or any other source.

What is the difference between ground reference speed and water reference speed?

What is the difference between ground speed and sea speed speed through water )?

What is the importance of speed over water in navigation?

Speed over water is only required to be used for collision avoidance and not necessarily for navigation. By using speed over ground, a navigator is more aware of the situation than otherwise. For example, if the ship is drifting towards a danger, navigator will know it better if he has speed over ground in radar.

Speed over water is the speed of the ship with respect to water. Or it is the speed of the ship with respect to something floating on the water. I have written a detailed article on speed over ground and speed through water and why it is required to be used for collision avoidance during navigation.

Why do we use speed over water for collision avoidance?

And that is the reason vetting companies require use of speed over water for collision avoidance. When we use speed over water the same situation would look as a head on situation. That is because when we use speed over water, it does not consider the effect of current on the vessel. But in both the cases, CPA and TCPA would not change.

What is the difference between ship speed over water and ground?

In the same way, the ship’s speed is either measured with respect to water or ground. Speed over water is the distance traveled in one hour with respect to water. Similarly speed over ground is the distance traveled in one hour with respect to ground.

https://www.youtube.com/watch?v=_6FKNljo4r4