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Old 22 August 2012, 10:54   #11
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Hi John,

glad you made it back safely!

Have just taken your boat out and glad to report there is no damage to leg, hull props, etc. In fact your props look very clean - just like they've been sand blasted!!!!
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Old 22 August 2012, 11:15   #12
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Thanks for sharing the lessons learned :thumbs and glad it worked out.
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Old 22 August 2012, 12:02   #13
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Well thanks for all the positive replies , still very pee'd off about making such mess.
Nasher glad to have you along any time but with my record are you sure?
I better do another night passage soon .
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Old 22 August 2012, 12:41   #14
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good all ended well, did you have DSC radio , if you had you could have used it to send and urgency call, or at worse a DSC Distress RED button.

This would send your GPS position.

If I was stranded on a sand bank I might have pressed the red button, ESP with breakers over the boat.

but hindsight is 20:20 , and time to think what what I do.

regards
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Old 22 August 2012, 13:04   #15
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Originally Posted by Jonny2488 View Post
Thanks for sharing. Glad it all ended safely for you both.

Not so sure about the "always believe your GPS" comment. Unfortunately there will always be times when the technology lets us down right when we need it the most (been there, done that, got the t-shirt).

At the end of the day there is no replacement for having paper charts and a hand bearing compass onboard, and arming yourself with a sound understanding of navigation.
you do realise compass and chart are not infallable either... compasses can get magnetic errors, users can mis-identify the point of reference, or plot it wrongly on the chart, and charts can be out of date etc.
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Old 22 August 2012, 13:08   #16
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I'd

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good all ended well, did you have DSC radio , if you had you could have used it to send and urgency call, or at worse a DSC Distress RED button.

This would send your GPS position.

If I was stranded on a sand bank I might have pressed the red button, ESP with breakers over the boat.

but hindsight is 20:20 , and time to think what what I do.

regards
I do have dsc fitted and specifically asked CG if they would like me to do as you say ,they said no so I assume they have thier reasons .
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Old 23 August 2012, 03:41   #17
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you do realise compass and chart are not infallable either... compasses can get magnetic errors, users can mis-identify the point of reference, or plot it wrongly on the chart, and charts can be out of date etc.
You have far more control over the accuracy of your navigation equipment than you ever will over the reliability of your GPS.

1. Go out and test/establish the magnetic effect the boat has on your compass before any night passage so you're aware of it.

2. Learn how to navigate properly to minimise user error when it comes to identifying objects/marks/points of reference. Believe it or not, it's quite a good system.

3. Just make sure you have up to date charts onboard - not difficult.

At the end of the day I'd trust my own navigation skills over any gps unit.

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Old 23 August 2012, 04:44   #18
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You have far more control over the accuracy of your navigation equipment than you ever will over the reliability of your GPS.

1. Go out and test/establish the magnetic effect the boat has on your compass before any night passage so you're aware of it.

2. Learn how to navigate properly to minimise user error when it comes to identifying objects/marks/points of reference. Believe it or not, it's quite a good system.

3. Just make sure you have up to date charts onboard - not difficult.

At the end of the day I'd trust my own navigation skills over any gps unit.

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I would tend to disagree with some of these points TBH...

Magnetic error on a compass fitted to a fiberglass boat with only the engine and nearby electronic equipment for it to be affected by is of minimal consequence when navigating in local waters.
I would be concerned if i was crossing the channel using only the compass as the small error would lead to a potentially large deviation. But who crosses the channel these days using only a compass?


In 20+ years at sea so far i have rarely seen a GPS unit read incorrectly...i have however seen the readings misinterpreted which is something completely different though.
Since our dear friends across the water removed the 'selective aquisition error', GPS signals have been very accurate indeed so much so that commercial shipping is now gradually switching over to full electronic charts (ECDIS). No paper charts at all are kept on many large commercial vessels relying purely on electronic navigation equipment GPS/DGPS, Gyro, etc...

Trusting your own navigation skills over modern electronic equipment i feel is foolhardy, if anything they should complement each other. There is nothing wrong with using chartplotters and other GPS equipment. I wonder how many groundings have been avoided since the cost of chartplotters have dropped over the last 10 years or so? Even the most inexperienced sailor can zoom in on a chartplotter and steer a course out of harms way. All it really takes is a good basic knowledge of tides and what the different colors/shading on the plotter represent and they should be OK for local cruising.
You say to keep up to date charts on board? OK, but would you be able to plot a position on these charts, at night time, without using a GPS LAT/LONG readout? At best you would come up with a "I'm somewhere around here" fix.
Its true that experience counts for an awful lot but learning to navigate 'properly' ('safely') takes a long time but even the most experienced of sailors will still use electronic aids to help them on their way.


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Old 23 August 2012, 04:46   #19
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You have far more control over the accuracy of your navigation equipment than you ever will over the reliability of your GPS.
Johnny I'm not suggesting for a minute that any one system is better than the other in all situations or that either system isn't much better if applied with a significant dose of scepticism and "Can that be right" when you look at the 'result'.

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1. Go out and test/establish the magnetic effect the boat has on your compass before any night passage so you're aware of it.
That assumes that (i) you know if anything changes. You find any/all artefacts (e.g. does the compass vary when the radio receives), that you remember in the heat of the moment and the dark to account for anything you find. Whilst electronic devices can fail, human beings do so much more often and less predictably. You are clearly the special type of person who never makes a mistake.
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2. Learn how to navigate properly to minimise user error when it comes to identifying objects/marks/points of reference. Believe it or not, it's quite a good system.
of course it is a good system. of course the more you do it the better you get, but it doesn't eliminate the possibility that you mis identify the mark (or can't find it), or mistransfer the information to the chart (especially on an open boat rather than the comfort of a chart table).
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3. Just make sure you have up to date charts onboard - not difficult.
oh really! So sandbanks never move or when they do the admiralty instantly gets updates out instantly? My usual cruising waters haven't been surveyed for over 100 years. Obviously the same issues apply to electronic charts, but you appear to have an undue faith in paper navigation as though it will be 'more correct'. I assume you've never had a chart blow away?

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At the end of the day I'd trust my own navigation skills over any gps unit.
Interesting - so if you plotted a point and it put you 1 mile out from the gps location you would assume your results are correct (and the GPS has suddenly developed a random malfunction) or you would go back and check your plotting and bearings? Personally even if after checking a hand plotted position I was that far off the GPS (and in any area where it mattered) I'd be proceeding with extreme caution as the likelihood of human error is far greater than the GPS getting an error that causes a positional error (which it doesn't report or 'trap') - its much more likely that your GPS just stops working than gives you massive position errors without warning.
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Old 23 August 2012, 05:03   #20
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Originally Posted by Jonny2488 View Post
You have far more control over the accuracy of your navigation equipment than you ever will over the reliability of your GPS.

1. Go out and test/establish the magnetic effect the boat has on your compass before any night passage so you're aware of it.

2. Learn how to navigate properly to minimise user error when it comes to identifying objects/marks/points of reference. Believe it or not, it's quite a good system.

3. Just make sure you have up to date charts onboard - not difficult.

At the end of the day I'd trust my own navigation skills over any gps unit.

Sent from my iPhone using Rib.net
Navigation is an art, and not a science, however from my experience the best navigators have very good "situational awareness", which means you know where you are, and all the inputs from all sources, GPS, visual, and sounder are all agreeing.

It is quite easy to loose situational awareness, and then you start making assumptions, and making the "evidence" fit to what you think you know.

One of the easiest ways to loose sit awareness is to be concentrating on one thing, and you exclude other things, such as focussing on avoiding pots, and not identifying a nav mark correctly.

It has happened to me a few years ago as a junior officer, I was focussed on fixing my position, and did not notice the ship that was on a collision course!

It is taught in a lot of bridge team management courses, and the only real way to deal with it is to know it can happen, and to question all of the sources of information.

I do rely on visual navigation, and knowing where I am, but this must be backed up and confirmed by GPS, as well as sounder data etc.

GPS can, and does give wrong readings, and charts can be wrong, as well as electronic charts also! combine all your skills, and make sure they all agree!

If not, stop, and sort it out.
Gary
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