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Dynamic positioning is
an automated system that allows a ship to stay in place
without the use of an anchor. |
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Dynamic positioning relies on pre-determined, satellite-fed information. This is a system that was developed about 30 years ago and which was primarily used on research, offshore drilling and oil exploration vessels that needed to have a means of accurate positioning. A differential Global Positioning System (GPS) method, provides the vessel with a degree of accuracy of within about 15 feet, as compared with a regular GPS system which has an accuracy rate of within 100 feet. |
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Programmed Readings |
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 Here's how it works:
When the ship's Master determines where he wants to
position a vessel, a series of calculations is made and
the readings are then programmed into a satellite console
by a Bridge Officer. There
after, the computer receives a
series of ongoing positioning information generated by
the computer and subsequently makes any necessary
adjustments to individual equipment -- such as stern or
bow thrusters, for example -- in order to keep the ship
true to the Captain's original calculations.The computer constantly checks to make sure the ship is adhering to the preset readings. If there are any deviations from these readings, the computer automatically makes the appropriate changes to compensate for such factors as wind or tides. Differential GPS is widely used in port navigation. In actuality, there are two dynamic positioning methods deployed in today's market -- the GPS system, which is based on satellite readings; and a second technique, which relies on readings dispersed from underwater transmitters. The alternate transmitter method of ship positioning is based on readings from underwater transmitters; it is an older, though still more precise system. However, transmitter positioning is more costly and limited in flexibility as the range of the readings depends upon where the transmitters are installed. In order to be effective, transmitters actually have to be planted near points where ships will anchor. You can't drop transmitters as the ship goes along. Rather, the transmitter system is used in the more stationary oil and research industries and in ship channels that are narrow and harder to transverse. |
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Environmental Benefit |
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Without a need to drop anchor, a ship
can hold her position and cause very little disturbance
to the surrounding ecosystem.
There is always some impact on the bottom of the sea,
albeit it is minor. With dynamic positioning, this issue
is automatically negated. And, in some highly sensitive
areas as the Cayman Islands -- where boats are actually
sent out to advise ships where to anchor -- dynamic
positioning is a welcome system.Another benefit of this positioning system is to passenger tendering operations because dynamic positioning can keep the ship across the wind and therefore provides good tendering opportunities on the ship's leeward side. Normally, when cruise vessels usually anchor, it is the bow anchor which is dropped, meaning the ship's bow is facing into the wind and resultant wind conditions are experienced on port and starboard sides, sometimes making for rocky tendering processes. It also makes the anchoring process faster to accomplish, as normally it takes quite a bit of skill and time to drop anchor. In employing dynamic positioning, however, operations costs increase and certain hardware, such as thrusters, are affected. In order to use dynamic positioning, the propulsion system must be running at all times. Also, thrusters have to be made from more durable material because of the additional wear and tear. Differential GPS also has a range limitation; because the satellite readings are beamed from an earth station, a ship must be about 200 miles in proximity of a land area in order to receive the signals. 
Despite the electronic advancement, new technology does
not replace old-fashioned skill. No matter what new
equipment is on board a ship, Navigation
Officers must still have the necessary skills to
handle these matters. Additionally,
bridge staff should also remember to not only look at the
screens, but look out the window as well.Meanwhile, manufacturers are making constant tweaks to the system and, this could open up new and different uses of dynamic positioning on cruise ships in the future. |
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