So how much do you trust your GPS - version 2

[FinesseChris]

GPS and transits

For what it's worth, I spent a fascinating half-hour on the bridge of the Portsmouth-CI (conventional) ferry as we came out of the Solent. The Master had all the gear, and plenty of people to monitor it (as well as at least three lookouts). He uses paper charts, in preference to though alongside a plotter, and says that he uses transits in preference to GPS when for example coming down the Little Russell.

I passing, he is also a great fan of AIS and reckons small boats with Class B are a help to him (and to themselves!) in poor vis.

Finally I asked him, as we crossed the end of Bembridge ledge, what he throught about pot markers: "We try to hit 'em!"

A comforting experience for a small boat sailor, as these guys are so obviously highly competent.

C

 

[srm]

GPS and our reliance on it can produce some lazy navigators . . . . They also get lazy about applying basic pilotage skills. A GPS is not always the best pilotage aid.

Agree totally, used to run STCW radar simulator courses for MN deck officers. If they did not cross check positions given by GPS we degraded it, if they did not notice the GPS degaded we made it worse until it was effectively turned it off. If they did not keep a paper plot at a realistic interval for the navigation situation we turned the plotter off . . . After a few days they soon got into the habit of check and double check . . . .

 

[mortehoe]

To the nearest foot .... both horizontally and vertically .....

except when it's being selectively blocked ie in the lower stretches of the Chesapeake Bay.

 

[Duffer]

Yes it is very easy to become over reliant on GPS as it is usually excellent. We had the same problem of being shown up the hill at Pontrieux on our plotter. As GPS receivers/plotters/laptops can fail without warning I suggest most of us should carry at least a handheld unit as backup (as well as suitable paper charts of course) ...

 

[lw395]

Yes it is very easy to become over reliant on GPS as it is usually excellent. We had the same problem of being shown up the hill at Pontrieux on our plotter. As GPS receivers/plotters/laptops can fail without warning I suggest most of us should carry at least a handheld unit as backup (as well as suitable paper charts of course) ...

A handheld unit is also useful for finding your yacht in fog, provided you mark it as a wp before going ashore.
It's also nice to be able to check the main gps. They do fail now and then, my last one got corrosion in the antenna and became progressively deaf.

 

[bbg]

Yes it encourages laziness

I just bought a boat, with dozens of waypoints helpfully put into the GPS. I have only used a couple, at the harbour entrance, to guide me in the general direction of home. Relying on bouys once I got to within a couple of miles.
Yesterday I decided to see just how accurately the waypoint had been put in, by sailing right past the bouy.
Not very accurately, as it turns out. Rather than plotting the position of the bouy, the waypoint seems to be mid-channel, between that bouy and its opposite number. Perhaps that is what the original owner intended, perhaps not.
But it made me realise that I would be foolish to rely on the accuracy of any waypoints I have not input myself. As much as it pains me to do so (that is the laziness part), I think I will have to delete ALL the waypoints and input new ones myself.
I suppose the task will be made much easier if I can figure out a way to do it all on a computer and hook it up to the GPS.

 

[colingr]

The previous owner probably did it on purpose. Putting exact coordinates for a buoy in is asking for a collision!

As you say it is safer to put your own in. A mark in the midle of the channel adjacent to the actual object in question is safer IMHO.

 

[bbg]

The previous owner probably did it on purpose. Putting exact coordinates for a buoy in is asking for a collision!

As you say it is safer to put your own in. A mark in the midle of the channel adjacent to the actual object in question is safer IMHO.

I agree that approach is safer, although it hadn't really occurred to me until I sailed past the bouy and the lightbulb went off that the waypoint was mid-channel. It made me think that I should input a mid-channel route of waypoints, in case I ever need to return in thick fog.
But what it also made me realise is that I cannot assume the accuracy of the waypoints that someone else input. Previous owner might have input every mark 100 meters out in one direction or another. I just don't know, so I think I have to start from scratch again.
I suppose that means the first step is to buy a chart.

 

[bilbobaggins]

I suppose that means the first step is to buy a chart.

I have a couple of those you could have, for a modest consideration. They were fine when I last used 'em in 1986......