What do cruise ships and such use for navigation?

Question

this adds to my other question about this. I really need help and doubt I'll find something I need from another resource. I love u, thanks!!!!

Answer 1

OK,just to clarify a couple of things...

GPS stands for Global Positioning System - nothing to do with "ground", and it doesn't transmit a signal and listen for a return.. that's radar.  GPS compares the timing of signals transmitted constantly by a chain of satellites.  

Computations based on the difference in signals received allow an estimate of position down to a few feet.

However, it would be silly to rely on just one system, especially for a large vessel. (Particularly since the GPS satellite chain is operated by the military of just one country, and could be disabled at a whim )

Most vessels will use a combination of several systems..   GPS, radar, visual observation and will always maintain an updated track on a good old-fashioned paper chart.  That way, if all the electronics failed, you might be able to find some grizzled old seafarer who can remember how to navigate with a pencil and paper. It's a dying art, but a few of us greybeards can still do it.... if you buy us a drink :-)

Answer 2

TOM TOM !

Answer 3

Some may even use a sextant. May not prevent collision with an iceberg though.

Answer 4

Well, speaking as a cruise ship navigator we use the following:

GPS - global positioning system, fixing our positon via satellites.

DGPS - same as GPS (the D stands for 'Differential') however there is an additional land station that sends out a correction for any errors in the GPS system for that area

Whilst many think D/GPS is the be all and end all of position fixing there are a number of serious drawbacks with it - principally that until the european system is fully functioning the beloved US govt can turn it off whenever that want.

Additionally you have to really check to see if the datum of the area you are sailing in corresponds to the datum the GPS system uses. Or to put into simple terms you can be over a mile off in some parts of the world, and if you are navigating near land that difference will be difference of staying aflot or running aground.

Because of this, and because of basic professionalism, we really dont like to use GPS as our primary position fixing method when we are sailing near to the coast.

In such situations one of our main position fixing tools are our radars by using such things as 'parallel indexing' (google it) and such like. our radars can also give a good indication as to the effect of wind/tide/current etc if used correctly.

if very close to land then we will use visual bearings of identfied headlands etc.

Inaddition to the above primary tools we also have a number of secondary tools such as:

doppler log - measuring our speed through the water/over the ground

echo sounder - measuring the depth of water (obviously if it is more or less than we are expecting things might be going worng on the navigation front)

radio direction finder - to get bearings off radio beacons

loran/decca - 'almost' defunct navigation systems using the propagation of radio waves

and of course the sextant (used with a chronometer, alminac, and a good understanding of spherical triganometry on an oblate object) which must not be underestimated as a very good navigational tool

im sure there are a couple ive missed off but they are the main ones that are used these days

Answer 5

Today's shipping rely on GPS   Ground position sensor  ( A transponder that sends a signal to a satellite and back to the ship telling the crew exactly where they are in the world!)

Answer 6

everything. GPS, sonar, cb radio, proximity sensors, wind, drag and flow sensors and a decent captain.

Answer 7

GPS

Most use satellite based GPS using systems from companies such as Thrane & Thrane.

Answer 8

SATNAV, GPS and if they are still smart enough, visual navigation.

Answer 9

Well I'm not going to argue with Masterlymayhem's answer. He's been there and doing that on a daily basis.

I will say its nice for ferretlover to say they love us though... awww shucks.

Answer 10

Cruise ships have a large slection of navigation instruments.  Heres a partial list:

1)A very accurate atomic clock, that listens to WWV and WWVW, which is accurate to 1 second every 32 years.  This clock is used to check longitude- the earth is divided into 24 time zones, and by knowing your time zone you know your longitude.

2)A chart- usually in this day and age, an electronic one that is tied directly into a GPS system which automaticly logs speed, direction, fuel useage, water salinity/temperature and sonar conditions.

3)A ships navigator/helmsperson- whos job is to drive the ship and figure out the course.

4)To show off to tourists, they have Sextants- which, if used with a nautical almanac will tell you your lattitude by looking at the sun at EXACTLY noon (You see the sun, you "bring it down to the horizon" and read the degrees) the problem is knowning when is exactly noon, local time- hence, the atomic clock listed above.  You can take star sights- theres over 60 listed in Bowditche's book and do the same thing.

5)A Ships radio officer/Officer of the deck whos job is to monitor weather conditions from NOAA and other international weather conditions, along with satellite downlinks.

However, once again, to show the tourists and the purists a highly accurate barometer is kept on display for show- nominally, it'll fortell the local weather some 12 hours in advance.

Answer 11

Radar Gps and a bevy of others