GPS and grounding.

[Uricanejack]

Having responded to MayDay calls from grounded boats on several occasions. I have observed they often they don't know where they are but can give GPS position to a couple of decimal places.

I looked up GPS on google and one respose was GPS kills and the story of an austrailian racing yacht grounding using GPS. no doubt done to death years ago it was in 09

I noticed several tongue in cheek threads re GPS and sextants.

I was wondering do you navigate by GPS alone.
I would come up with a pole but I don't know how.

 

[single]

I don't but i know loads of folk that do especially flying.I prefer radar where i sail using coastline features and racons/buoys.Longer passages compass,chart and gps plots to double check.All seems to work out ok.

 

[VicS]

Having responded to MayDay calls from grounded boats on several occasions. I have observed they often they don't know where they are but can give GPS position to a couple of decimal places.

I looked up GPS on google and one respose was GPS kills and the story of an austrailian racing yacht grounding using GPS. no doubt done to death years ago it was in 09

I noticed several tongue in cheek threads re GPS and sextants.

I was wondering do you navigate by GPS alone.
I would come up with a pole but I don't know how.

You can add a poll by scrolling down to "Additional Options" and clicking on "Post a poll " But you can only do it when first posting and only to a new thread.

If you dont see "Additional Options" it is because you need to go to your User CP
Find "Edit options" and then change the "Message Editor Interface" to "Standard Editor" instead of "Basic editor". You will then have loads more formatting tools and other bells and whistles to play with.

To return to the GPS issue... I've never had the fortune to sail with a GPS. If I had one I'd probably use it more than I would at the moment think I would.

Id certainly read the position from it in the situations you give but I hope I would also know where I was as well.

 

[LittleSister]

Having responded to MayDay calls from grounded boats on several occasions. I have observed they often they don't know where they are but can give GPS position to a couple of decimal places.

Saint Tom Cunliffe puts it very nicely something along the lines of pilotage generally doesn't involve so much knowing where you are, as knowing where you're not!

I suspect that not understanding this is what leads some to have inordinate faith in the idea that having a gadget which will indicate their position to several decimal places will keep them safe.

 

[LadyInBed]

I was wondering do you navigate by GPS alone.

No, I let the GPS move a little boat icon on my chart plotter which tells me where I am, and set up the chart plotter to leave a line indicating where I have been and also projects a line to tell me in which direction I am going.
The end of the projected line tells me where I will be in two hours.
If I an going up or down Channel I pop in a WP on the chart plotter, press Goto then press Track on the Autohelm so I can sit back and enjoy the trip.
Every hour I write down this info so I can look back on it years hence to see where I have been

 

[John.edwards]

The Australian grounding in 2009 resulted in 2 deaths as a racing yacht hit flinders islet. the investigation revealed that at the toime of the incident the GPS satellite configuration was particularly poor resulting in a larhe dilution of horizontal precision. of the 6 or 7 satellites up, only 3 or 4 were useable and the error in location probably exceeded 100m.

 

[Tomahawk]

I use the chart plotter gps for position..
The use the radar overlay to confirm that the plotter has me in the right position..

 

[davidaprice]

The Australian grounding in 2009 resulted in 2 deaths as a racing yacht hit flinders islet. the investigation revealed that at the time of the incident the GPS satellite configuration was particularly poor resulting in a large dilution of horizontal precision. Of the 6 or 7 satellites up, only 3 or 4 were useable and the error in location probably exceeded 100m.

In cases like that the GPS knows that its result is not precise, and e.g. my Garmin handheld chartplotter draws a big circle showing the radius of uncertainty. Usually the circle's so small you can't see it: in general use my device's precision is less than a boat-length.

Here in Finland the waters are not tidal, and navigation is mostly pilotage through dense well-marked archipelagos with underwater rocks all over the place; I navigate using the chartplotter continually, but look ahead on the paper chart so I know which marks I should be seeing, and make sure I always know where I am on the paper chart.

We have a backup handheld chartplotter in case the first one dies, and Navionics in a smartphone.

 

[[70521]]

I was wondering do you navigate by GPS alone.

No. My GPS is one of the tools in the tool bag. I like to use traditional methods of navigation and then check it against the GPS. I know it is far, far more accurate than me but one day there is going to be a power issue and as a colleague used to say "use it or lose it!"

 

[Ex-SolentBoy]

I always know where I am. Either by looking around or looking at the plotter/iPad or whatever.

If those failed I have other plotters, an iphone and handheld.
If those failed I have a Mac and a dongle.
If those failed I have paper charts a compass and a watch and radar.
If those failed I have a sextant and tables.
If those failed I could use my brain to make some reasonable assumptions.

If THAT failed it wouldn't matter what else I had.

 

[FWB]

In cases like that the GPS knows that its result is not precise, and e.g. my Garmin handheld chartplotter draws a big circle showing the radius of uncertainty. Usually the circle's so small you can't see it: in general use my device's precision is less than a boat-length.

Yes I display the estimated position error on my plotter.
Even that doesn't tell the whole story but it is useful info.

 

[Otter]

No, I let the GPS move a little boat icon on my chart plotter which tells me where I am, and set up the chart plotter to leave a line indicating where I have been and also projects a line to tell me in which direction I am going.
The end of the projected line tells me where I will be in two hours.
If I an going up or down Channel I pop in a WP on the chart plotter, press Goto then press Track on the Autohelm so I can sit back and enjoy the trip.
Every hour I write down this info so I can look back on it years hence to see where I have been

Good enough for me. Damn sight better than RDF beacons - remember being hunkered down trying to listen to the morse code? Damn sight more reliable than LORAN which I found on one North Sea crossing to Sweden was much less accurate than dead reckoning - we'd confirm where we actually were by the oil rigs. GPS is reliable and dependable, just needs some common sense and the realisation that it can be wrong sometimes - just not very often.

 

[capnsensible]

In pilotage, what can beat a handbearing compass, echo sounder and a simple plan, transits or clearances?

Contours work in fog too.

 

[AndrewB]

Having responded to MayDay calls from grounded boats on several occasions. I have observed they often they don't know where they are but can give GPS position to a couple of decimal places.

When sailing along the US Intra-Coastal Waterway we came across a place (the entrance to the Indian River) where the main channel had recently moved. A sand bar had practically closed the old channel. It was obvious enough. The gulls were standing on the bottom where the channel had been, while the new channel was evident from the darker water.

Forced to choose between what their GPS chart plotter was telling them, and the evidence of their eyes, quite a few boaters opted for the former. A local yard was doing great business towing off and checking up to five a day, at $3,000 apiece.

 

[Conachair]

I was wondering do you navigate by GPS alone.

No it's always a fairly constant process of checking if it all tallys up with what's going on , visual from buoys, transits, rough bearings to chimneys etc, depth, etc etc.

I'm quite often wrong, for a moment or 2 anyway, it's so easy to see what you want to see. All that Mk1 eyeball being the best is rubbish, pretty good quite often but don't trust it all the way, often it sees what it expects to see.

The gps/charts haven't been wrong so far.

Yet anyway, first time for everything. Don't trust anybody or anything, they're all out to get you

 

[NormanS]

You have to remember that GPS Lat and Long positions are probably more accurate than paper chart positions. Sometimes the Plotter will show that you are travelling over the land. A certain amount of common sense is useful. GPS is good for navigation, but eyes are probably better for pilotage.

 

[Perry]

I know a guy who had a nice shiney hand held GPS and we where on passage from the Hamble to Cherbourg and he really couldnt get it that the isle of Wight was in his way,
all the way over he was crying that we where miles off course and where doomed, even as we went straight through the middle of the East entrance he reconed that we where wrong, it turned out that his way point was the centre of the outer harbour wall.

 

[sailor211]

Id certainly read the position from it in the situations you give but I hope I would also know where I was as well.

The problem is that I do not know my lat/long al the time. So last time I was passing a yacht whth a problem, it was some minutes between hearing the mayday to getting it into my head that I was near to plotting the position. Single handed I had to keep a look out at the same time. If the call had given the position as 1/2 mile SW of Poole channel I would have known imediately.

I recall a conversation between the coastguard and a yacht on the mud. The Coast guard ended by saying is that the mud at the eastern entrance to Cowes. Easy to spot the man in trouble then.

 

[NormanS]

The problem is that I do not know my lat/long al the time. So last time I was passing a yacht whth a problem, it was some minutes between hearing the mayday to getting it into my head that I was near to plotting the position. Single handed I had to keep a look out at the same time. If the call had given the position as 1/2 mile SW of Poole channel I would have known imediately.

I recall a conversation between the coastguard and a yacht on the mud. The Coast guard ended by saying is that the mud at the eastern entrance to Cowes. Easy to spot the man in trouble then.

Once all the Coastguard operate from a headquarters in Milton Keynes, Lat and Long will be the only way to give them your position.

 

[jordanbasset]

The time I came close to grounding was when I did not have the chartplotter/gps on as I thought I knew where I was