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Parts of the pattern may be obscured by the effects of propeller wash, and tail eddies behind the boat's stern, and by the boat being a large object and not a point source. The water need not be stationary, but may be moving as in a large river, and the important consideration then is the velocity of the water relative to a boat or other object ...
This motion is generated directly either by the water and wind motion, particularly lateral wave motion, exerting forces against the hull or by the ship's own propulsion; or indirectly by the inertia of the ship while turning. This movement can be compared to the vessel's lateral drift from its course.
Waterfowl and boats moving across the surface of water produce a wake pattern, first explained mathematically by Lord Kelvin and known today as the Kelvin wake pattern. [ 1 ] This pattern consists of two wake lines that form the arms of a chevron, V, with the source of the wake at the vertex of the V.
The legs of water beetles have little hairs which spread out to catch and move water back in the power stroke, but lay flat as the appendage moves forward in the return stroke. Also, one side of a water beetle leg is wider than the others and is held perpendicular to the motion when pushing backward, but the leg rotates when the limb returns ...
This allows operations at sea where mooring or anchoring is not feasible due to deep water, congestion on the sea bottom (pipelines, templates) or other problems. Dynamic positioning may either be absolute in that the position is locked to a fixed point over the bottom, or relative to a moving object like another ship or an underwater vehicle.
If a vessel runs directly against a current or directly with a current, the speed of the vessel and speed of the current can be added or subtracted from each other. Such as, a vessel has a speed of 8 knots through the water and the vessel is traveling with the current, which is at 2 knots, then the speed over ground is 8+2 and the vessel's true ...
The water, coming from the propeller, gets a cone shape, widening when it leaves the propeller. If the rotating water cone contacts the ship's hull, a sideways force is generated. Propeller walk is hardly noticeable when sailing forward, since the propeller water will not hit a large surface of the ship's hull and corrections to the ship's ...
Also velocity as well as the external factors that have influenced the course either partially or entirely, such as the wind and/or the current (bearing of the current and hourly current intensity). The point obtained from the calculations is called the "Dead reckoning location", with its corresponding latitude and longitude .