GPS Assisted Collision

[tome]

With standalone GPS accuracies in the order of a boat length, there is a danger of collision which is similiar to that which existed when mariners used Decca lanes to converge on harbour entrances.

This is especially the case when we use published waypoints. As we all converge on the same spot in low viz, there is an inevitability that sooner or later a GPS assisted collision will occur. Does anyone have any experience of this?

Far better to derive your own waypoints, deliberately offset from any you see published...

 

[milltech]

I made a calm windless night passage from Dartmouth to 5 miles off Portland and kept company with two sets of lights near me all night, and NEVER during my watch was there a moment when both red and green were not visible on the bow.

As each boat passed a minor passage adjustment made all safe, but I thought that a couple of high speed hulls in 200 yards of visibility relying on radar might have an uncomfortable moment.

I sat next to man on an aeroplane who had been part of the team that developed automatic landing and he said they'd had to build in an error to stop runway damage as everyone bumped on the same few square yards. I guess the next Garmin development will ask you how much off track error you wish to have on this passage, and how close to the mark do you want to be before you come back onto track.

John

 

[Viking]

This was always the fear in Decca days. I use to use Chichester Harbour and the Bar Beacon was a well known waypoint. In the yacht club we all had our own position for the entrance and the bar. (Yes we had two one for the Harbour entrance the other for the club bar) But then with small entrances to some marinas and harbours in fog its going to be a problem if your vocused on the GPS and not 'heads up'. You can't hope the over chaps got the radar. 'Eye-ball' navigation is still the best.
PS In fact today I have just brought my first GPS set (Magellan 320)- as anyone got the instruction book in English mines in Norwegian. (it would be as I live there)

 

[jimi]

Quite apart from colliding with other craft, there probably is a danger of colliding with the object waymarked particularly if using an autopilot interfaced with the GPS! No excuse for not maintaining a proper seamanlike lookout!

 

[rogerroger]

320 manual

http://www.magellangps.com/PDFs/gps3153.pdf

what's it like ? I'm considering getting the 310 as a back up to my main Garmin 128

Roger Holden
www.first-magnitude.co.uk

 

[jimi]

Re: 320 manual

I've got the 315 as a backup and have used it several times as I've been stupid enough to fit the main one at the chart table! I find it excellent although it takes a lot longer to acquire satellites ..no surprising really on a handheld.

 

[Viceroy]

I've heard about but can't document, collisions and near misses on routes from Miami (Florida coastal cities) to Bimini (and other Bahama isles). Many vessels on same course/reciprocal course and many travelling at high speed. Similarly, I have experience with weekend crowds travelling between the greater Vancouver, B.C. area to the Gulf Islands/San Juan islands...occassionally nasty close quarter manuevering. Just be careful and plot your own way points. Cheers, Richard.

 

[Mirelle]

Yes.

The thinking man, on passage from Singapore to Hong Kong or vice versa, used to steam ten miles to starboard (more or less) of the direct route, a few years ago, when GPS first became the order of the day. Now he steams an odd fraction of a distance to one side, because everyone else is doing it!

 

[rogerroger]

Re: 320 manual

I'd never be without the GPS at the chart table - GPS does spoil sailing to an extent. I really quite enjoyed the first few weeks of having my boat before I installed GPS. First trip I did with it installed was Chichester to Brighton - totally easy but I still found myself nipping down to the chart table to check the position!

I want a handheld for emergeny back up - I'll keep it in the grab bag with the HH VHF. I've installed a GPS repeater in the cockpit which is dead handy, not so much for position but to be able to compare SOG and water speed to get a good idea of what the tide is doing..

(blimey, I'm rambling, must be time to go home...)

Roger Holden
www.first-magnitude.co.uk

 

[jimi]

Re backup HH GPS

I've tended to use the backup when short(single) handed when I ca'nt really leave the cockpit and wish to be sure of COG.

 

[Chris_Robb]

Going from Lezadrieux to Tregier by the inshore route we had thick fog. I deliberately set my waypints so that I would be on the starboard side of anyone coming east. Had several close visule sightings but always on the Port side. I have installed radar now as it was a bit scary - happy about the rocks - it was the other boats!

By the way the radar dows not pick up the average yacht without a radar reflector if head on or stern on to you. These boats became very visible as they came abeam and that was when we noticed the lack of Radar reflectors on the invisible yachts.

 

[jimi]

Alcohol assisted collisions

I suppose that's what you get from waypints!

 

[nightjar]

You have got to the nub of the question; the responsibility for safe navigation remains with the skipper irrespective of whether standard waypoints or your own are used. The GPS is only a Nav AID that tells you where you are; its your responsibility to decide if you want to be there in fog etc. !
Agree with the comment below re small craft and yachts without reflectors they will in many situations get missed or lost in the clutter; thankfully the slab sided metal jobs show up quite well.
Here's hoping for fog free sailing this year.......anyone cross the channel last year on the bank holiday end of May.......not nice!

 

[pvb]

Published waypoints...

Published waypoints can be wrong, so it's a good idea to check them against the chart. My habit is always to change them by about 0.2 minute, by rounding up or down - this makes entering the data quicker too.

 

[Jeremy_W]

yes, AND?

Come on "Mirelle" you can do better than that with your shipping industry contacts! How close are the near misses these days?

 

[LadyInBed]

Re: 320 manual

Had a 320 for a couple of years now. Found it to be V good. Got software to down load all my waypoints from the PC which worked a treat. It would have been a real pain putting all of them in by hand.

 

[Mirelle]

Available data

Near miss reports have been compiled by the Nautical Institute and published in their journal - "Seaways" - for some years now. The number of actual collisions has fallen dramatically, for a host of reasons including TSS, VTS and ARPA, but the point I was making is that professional seamen are well aware of the risk which Tome rightly alludes to, and act accordingly.

 

[Viking]

Re: 320 manual

Hi RR
To easly to say, I still have to get round the Norwegian - back to my 'norsk kurs' (Norwegian class). (thought!) perhaps I could E mail Knut Frostad on 'djuice' hes going so slow even I could keep up!