The Loran Came Back....

[westernman]

if technology allows this facility to be avaialble and accurate to a couple of feet, why not

I am just trying to understand how people use their GPS's. Would you drive a container ship into port relying purely on the chart plotter and GPS?

May be they do for all I know.

 

[Otter]

Yes they do, it's used to aid the stability programme that maintains the heading and speed of the ship.

Some of the comments though present a binary view of life, it's either paper, compass and log at all times and in all places - or you've sold your navigator's soul to the devil and never even look out of the window, just follow the route on the plotter.

It's a bit woolly liberal third way of me, but I use paper charts when occasionally appropriate, a compass rather more often and a GPS all the time, usually with a plotter screen on in the background. Sometimes I'll mainly use the paper chart, particularly for new places. Long passages where tidal off set are required can only really be done on a big paper chart, plus the children can follow our progress.

Back to the OP, it's a bit time the UK started to get some independence, we need to produce more of our energy; make more of our own laws; and as the country who invented worldwide commerce we out to have our own nationally controlled positioning system, it's not even that flipping expensive.

 

[macnorton]

I am just trying to understand how people use their GPS's. Would you drive a container ship into port relying purely on the chart plotter and GPS?

May be they do for all I know.

They use a pilot who navigates using local knowledge and a compass, gps can be wrong that's why it is a navigation aid.
If gps is so good why are ports reinstating Loran ?

 

[William_H]

They use a pilot who navigates using local knowledge and a compass, gps can be wrong that's why it is a navigation aid.
If gps is so good why are ports reinstating Loran ?

In ports around here they use Differential GPS. Here a GPS reciver is set up on land in a known location. It monitors the GPS signal and determines errors at the time. These errors are broadcast on VHF to GPS sets set up for differential GPS. When the ship GPS is corrected for errors then accuracy can be down to a few feet. Enough to pilot really large ships into ports. (still need a pilot though)
This differential GPS was also used for a contractor to locate and register the position of my swing mooring. A bit of a joke in that it was located and registred in one location. Several years later I needed a contractor to check and give a report to the authority. He called for a new mass (a railway wheel) I had no choice needing the report to be accepted by the authority. He insisted on planting the mass about 3 metres from the original. he reckoned the DGPS was that accurate and the original must have been wrong.
DGPS is also used by surveyors of land. The area of accuracy of corrected DGPS is approx equal to the range of the VHF link ie 80 odd miles in diameter. In some cases the local correction system is set up for free by government in some cases set up by companies and available on subscription.

However ordinary GPS is fairly accurate in relation to other recivers if not in absolute location. So in the sailing championships here some years back there were receiver reporting devices on all competitor boats, race management boats and buoys. When the big picture was colated on screen you could see quite accurately how far a competitor was away from another competitor, a buoy, start line etc. Any GPS errors affected all the receivers so relative position was acurate.
As for that original link to a journalist's story on how GPS is so vital to ships. Exageration was obvious. A clock may be corrected by GPS but will still be pretty accurate without GPS. A Gyrocompass may be aligned intially by GPS but will be accurate after a while without GPS. Assuming he is talking about a true gyro compass not a gyro stablised magnetic compass which also will be fine without GPS. Likewise radar should still be usable. It seems to me that journalists will often listen to one man's exageration (usually for commercial profit) then add his own exageration so that story often ends up with little reference to truth or fact. The more technical the more inaccurate. my little rant. olewill

 

[andygc]

They use a pilot who navigates using local knowledge and a compass, gps can be wrong that's why it is a navigation aid.
If gps is so good why are ports reinstating Loran ?

A few years ago I was a guest on the bridge of a British warship, leaving Devonport. The watch officer used traditional methods to follow the difficult, twisting channel - compass, pelorus, chart. The captain monitored his progress with his newly-issued laptop. Had the watch officer used the laptop, he'd have been properly in the channel. The captain pointed out where he'd gone wrong, but still said "well done". I don't know how much you know about manoeuvring ships in confined waters, but I doubt you'll find many professionals who don't regard GPS as a hugely valuable primary navigation and pilotage system.

Of course GPS can go wrong. So can people - the commonest cause of both maritime and aviation accidents is human error, not technical failure. What possible reason can there be to criticise the introduction of an alternative electronic positioning system, or to pretend that chart plotters and GPS are not primary navigation systems, particularly for commercial operators? You're going to do really well if you manage to take a bearing on an AIS Virtual Aid to Navigation with a hand bearing compass.

 

[RAI]

If gps is so good why are ports reinstating Loran ?

I don't think the ports are reinstating Loran. The GLA is promoting it and providing one tower. But for Loran to work, two other distant towers are needed. Those are being closed down. Why? - Try finding a cost-effective loran or eLoran receiver.
By the way, Loran doesn't like thunder storms, the lightning messes up reception. Lightning occurs more frequently than the threats to GPS reception.