Ex-SolentBoy
Well-Known Member
I am at risk of sounding like a broken record, but I shall do so anyway.
If you install the aerial INSIDE the boat (mine is next to the chart table and under the side deck) all of those issues go away.
GPS failure and the sextant.
- Thread starter capnsensible
- Start date
I am at risk of sounding like a broken record, but I shall do so anyway.
If you install the aerial INSIDE the boat (mine is next to the chart table and under the side deck) all of those issues go away.
D
Deleted member 36384
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The damage to the permanent antenna cable which resulted in the tin foil repair is independent of antenna position, the fatigued antenna cable to plotter join would still exist no matter where the antenna is mounted as I will still remove the plotter from the cockpit for safe storage below.
However, I do agree with the point you make about the antenna being down below. In my case this would only protect the antenna from moisture ingress. I don't even mount the antenna now. It stays attached to the plotter and is wedged into the corner of the spray hood / coaming interface. At the end of the sail I just disconnect the power and lift plotter and antenna down below.
wotayottie
Well-Known Member
Yes. You arent really analysing the risks in a rational way and your comments do smack of a mind made up.
Both systems rely on heavenly bodies, satellites and stars. First risk therefore is that these become unavailable. With the sextant this is common in our latitudes due to weather / clouds and time of day. Muchj less frequent in my experience is that its possible to lose satellite reception through electrical storms. Once in 20 years for me.
The second risk is equipment failure. Here I am handicapped by never having used a sextant in anger but I guess it is a relatively delicate piece of kit which can go out of adjustment if dropped on a bucking boat. And it also needs an accurate timepiece which for most of us is a battery powered electronic one just as likely to fail as a gps set. Equipment failure for a gps set isnt likely - its never happened to me - but even then you need to have in mind that for the price of a decent sextant ( anywhere between £350 and £1000) you can buy at least 3 hand held gps sets plus dozens of long life batteries.
The third risk is operator failure. With a sextant you have to use tables and people make silly errors doing those sorts of calculations. You would use a calculator? But thats another piece of failure prone electronics isnt it. And even when the operator gets it all right, how accurate is a sextant plot?
I think you can make a very good case for knowing how to use a sextant - tradition, personal skills etc. But an argument to use it seriously is like saying you dont trust engines so your boat will just have oars.
It's 2012
P.S. Do you sail a long keeler? Heavy? Gaff rig maybe? Baggywrinkle?
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jwilson
Well-Known Member
Yes - lots of water sloshing around inside the cabin took out all the electrics for a while, and on getting out the spare "waterproof" handheld found that it too had water inside.
Carried on with DR/astro until the handheld revived after a fresh water bath and spell in the oven.
On a previous occasion also had all electronics dead (again water-related, boat had been inverted) but no worries about GPS as it had not yet been invented in 1979.
SeamanStaines
Well-Known Member
Not really answering capnsensibles question but there is a real issue here. The average boat (with crew) has probably half a dozen GPS units on board, practically every phone now has a GPS built into it which will get a fix eventually, even without a connection so it is very, very unlikely that you would not have something that works. Take us, there is the ships system which actually has three GPS devices (ais transponder, masthead air station and the original ray marine sea talk device). Then I have a USB GPS as an backup tha goes into a pc (I think I have an old one kicking around as well). Then there is the 'official' backup in the form of a garmin handheld. Three iPhones and two iPad, so I reckon at least eight devices. I think there is a GPS in the spot emergency device, oh, one in the personal ais transponder and one in the EPIRB. The microwave probably has one as well (just remembered the burglar alarm has one and the ships wifi as well)
The problem is if/when the satellites fail, either because of a major system failure or the Americans getting excited! It is worth remembering the system is now old and I believe there are no 'spare' satellites in the mix so as/when they fail there will be gaps in coverage. Having a sextant and practicing using it means you are independant from that technology. Not an issue sailing around the med for sure, but might be more exciting mid pacific!
The problem is if/when the satellites fail, either because of a major system failure or the Americans getting excited! It is worth remembering the system is now old and I believe there are no 'spare' satellites in the mix so as/when they fail there will be gaps in coverage. Having a sextant and practicing using it means you are independant from that technology. Not an issue sailing around the med for sure, but might be more exciting mid pacific!
TimBennet
Well-Known Member
That's no problem - you can use the time readout on your GPS. Oh, hang on . . . .
Vara
Well-Known Member
I have three, sometimes four GPS systems all with independent power and antennas.
For my mainly coastal cruising backed up with charts, compass and echo sounder I think I'm pretty bombproof.
Maybe a lead line if I lose all leccy.
Sextant would bring very little to the party.
Oh and since my first GPS Trimble never had a GPS failure.
For my mainly coastal cruising backed up with charts, compass and echo sounder I think I'm pretty bombproof.
Maybe a lead line if I lose all leccy.
Sextant would bring very little to the party.
Oh and since my first GPS Trimble never had a GPS failure.
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noelex
Well-Known Member
The GPS system is getting better.
The numbers of working satellites is increasing not decreasing.
Neil_Y
Well-Known Member
I was unlucky? fixed Garmin went down due to wiring connection to pushpit aerial, then fired up an almost new Garmin45 hardly used as it was always a back up, within 12 hours the screen failed from moisture, then the last backup a Garmin 72 also old but rarely used it also suffered screen failure from moisture ingress. The weather was horrible with horizontal rain and spray, the handhelds needed to be used in the open to get a fix and neither were water proof.
I've told the story here before but we were approaching Caruna in November when this happened and the sextant came in very useful as a distance off fix on the one lighthouse we could see.
So yes it happens, but I guess rarely. I do love the fact that the well cared for sextant has many uses in coastal and ocean navigating. I'm amazed at how many people just trust in a remote system to always tell them where they are, I like to know for myself that I can work out where I am. I use GPS as an aid and it's quite useful but I always have an alternative.
I've told the story here before but we were approaching Caruna in November when this happened and the sextant came in very useful as a distance off fix on the one lighthouse we could see.
So yes it happens, but I guess rarely. I do love the fact that the well cared for sextant has many uses in coastal and ocean navigating. I'm amazed at how many people just trust in a remote system to always tell them where they are, I like to know for myself that I can work out where I am. I use GPS as an aid and it's quite useful but I always have an alternative.
Sans Bateau
Well-Known Member
Friend of mine crossed the Atlantic both ways in the mid 90's, with charts and a Garmin 12XL HH GPS. When I asked him about astro nav as an option he said to me " at the time you will really need it the deck will be bucking like a bronco, or/and there will be 99% cloud cover, so whats the point these days". Tend to agree.
jwilson
Well-Known Member
Nothing helps electronics much once substantial quantities of salt water get put inside the boat and shaken around.... Had it happen twice, once in serious survival conditions, and once with a hard-driven race boat that developed a significant and at the time untraceable leak in fairly rough but not remotely survival conditions. Pumping for a minute or so every time a few basinfuls made their way above the floorboards - about every half hour - kept it down but the way water sloshes around in a flat-bottomed modern boat it got everywhere. Turned out later there was a leak round the exhaust flange on the transom, normally a foot out of the water, but driving hard offwind submerged it.
fishermantwo
Well-Known Member
Obviously a modern gps antenna is waterproof and much more sensitive and should be mounted in the cabin where it can not be damaged. Highly unlikely that all the ships batteries will fail at the same time. Jumper-leads from the batteries to the GPS and other equipment are quick and cheap to make up. Have a selection of ends to suit and stow it away in the chart table where it hopefully will never be needed.
jerrytug
N/A
Would it have turned sight reduction tables to papier maché,as happened to Shackleton,M.Richey,etc.?
Roberto
Well-Known Member
Professionals and astro ?
I went through the MCGA code for small commercial vessels and the only reference I found to position finding equipment is section 18.3.2 point 1. (from MGN 280)
A receiver for a global navigation satellite system or a terrestrial radionavigation system,
or other means suitable for use at all times throughout the intended voyage to establish
and update the vessel’s position at all times.
Which indicates that a GPS *or* another means of positioning "for use at all times" is compulsory, I do not think the sextant can be considered as a positioning device "at all times", even if it was the code requires one or the other.
It does not appear that a spare GPS is required.
Is there some other relevant section where sextant is defined as compulsory equipment on small commercial vessels ?
Just gone through the ISAF Offshore Special Regulations, they "recommend" (point 4.11.2) sextant tables and timepiece, still not compulsory.
(Just asking, BTW I like astro navigation, this was my first sight about twenty years ago )
I went through the MCGA code for small commercial vessels and the only reference I found to position finding equipment is section 18.3.2 point 1. (from MGN 280)
A receiver for a global navigation satellite system or a terrestrial radionavigation system,
or other means suitable for use at all times throughout the intended voyage to establish
and update the vessel’s position at all times.
Which indicates that a GPS *or* another means of positioning "for use at all times" is compulsory, I do not think the sextant can be considered as a positioning device "at all times", even if it was the code requires one or the other.
It does not appear that a spare GPS is required.
Is there some other relevant section where sextant is defined as compulsory equipment on small commercial vessels ?
Just gone through the ISAF Offshore Special Regulations, they "recommend" (point 4.11.2) sextant tables and timepiece, still not compulsory.
(Just asking, BTW I like astro navigation, this was my first sight about twenty years ago
)
Tomahawk
Well-Known Member
You asked now many people have had GPS failure?
We had a spat of toys throwing themselves out the pram in the dark whilst approaching the Solent...
First the plotter stopped updating
Then the secondary GPS packed up because the arial was being blanteted by the rigging
Then the handheld refused to turn on
Lets just say I am glad I knew roughly where we were and it was a clear night
We had a spat of toys throwing themselves out the pram in the dark whilst approaching the Solent...
First the plotter stopped updating
Then the secondary GPS packed up because the arial was being blanteted by the rigging
Then the handheld refused to turn on
Lets just say I am glad I knew roughly where we were and it was a clear night
PeterR
Well-Known Member
I've had minor failures of GPS output to the plotter as the wiring loom is a bit vulnerable to over enthusiastic searching in the cockpit locker. That of course did not affect my handheld GPS.
However, in the early days of GPS, towards the end of a crossing from Guernsey to Plymouth the GPS started to tell us we were doing 15 knots across the top of Dartmoor. It carried on doing that for about 2 to three hours before it started to agree with our manual fix (three point fix from lighthouses).
The set had never given trouble before and never did again after that incident. We never found out the cause of the problem but it was a period of high sun spot activity or perhaps the RN were playing games.
However, in the early days of GPS, towards the end of a crossing from Guernsey to Plymouth the GPS started to tell us we were doing 15 knots across the top of Dartmoor. It carried on doing that for about 2 to three hours before it started to agree with our manual fix (three point fix from lighthouses).
The set had never given trouble before and never did again after that incident. We never found out the cause of the problem but it was a period of high sun spot activity or perhaps the RN were playing games.
James_Calvert
Well-Known Member
For what it's worth, I had a Dinghy Decca for a few years. Never failed as an instrument, except when the aerial snapped off. But it did have some dodgy moments between Decca chains.
I've since had a series of handheld GPS, albeit permanently connected to the ship's supply in holders by the chart table.
The first one - a Magellan - eventually failed totally.
The second one - a yellow french make - started buzzing and occasionally turning itself off. I still have this, but don't expect it to be still working when I look at it, and I am seldom surprised.
The third one, a Garmin 72 has been fine. But because of the unreliability of the yellow one, I got a second Garmin 72 as a spare, and use one in the cockpit, leaving the other one in its holder below.
However I have found that one of the Garmins now has a tendency to turn itself off when it gets a slight bump in the cockpit. So of the three I've got, only one is - at the moment - wholly reliable.
Not saying a sextant would meet my needs - it wouldn't - but just pointing out that anything relying on electric string to keep working can fail, my experience with GPS sets is that they do fail, and of course you have no warning of when this will happen.
I've since had a series of handheld GPS, albeit permanently connected to the ship's supply in holders by the chart table.
The first one - a Magellan - eventually failed totally.
The second one - a yellow french make - started buzzing and occasionally turning itself off. I still have this, but don't expect it to be still working when I look at it, and I am seldom surprised.
The third one, a Garmin 72 has been fine. But because of the unreliability of the yellow one, I got a second Garmin 72 as a spare, and use one in the cockpit, leaving the other one in its holder below.
However I have found that one of the Garmins now has a tendency to turn itself off when it gets a slight bump in the cockpit. So of the three I've got, only one is - at the moment - wholly reliable.
Not saying a sextant would meet my needs - it wouldn't - but just pointing out that anything relying on electric string to keep working can fail, my experience with GPS sets is that they do fail, and of course you have no warning of when this will happen.
ytd
Well-Known Member
never had a gps failure but have lost signal for short periods especially when close to military exercise areas.
I agree with TimBennet's posts. Well put.
I wonder how long astro would remain as popular and intellectually stimulating as poster here argue, if it was dropped from the RYA Offshore syllabus.
I agree with TimBennet's posts. Well put.
I wonder how long astro would remain as popular and intellectually stimulating as poster here argue, if it was dropped from the RYA Offshore syllabus.
Sybarite
Well-Known Member
Not GPS but a Decca failure. Sailing from Scilly to Arklow i lost the signal and never found it again. The rest of the journey, there and back to S Brittany was done using DR.
noelex
Well-Known Member
(Just asking, BTW I like astro navigation, this was my first sight about twenty years ago
I bet you still have the sextant, but I hope the hat hasn't survived.
