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  #11  
Old 03-09-2007
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Quote:
Originally Posted by TrueBlue
A chartplotter depends upon coordinates provided by a Global Positioning System antenna/receiver. The chartplotter is integrated with and reliant upon the GPS to function properly.
And paper charts and plottting are depend upon a human... Human error in todays day and age is far worse than computer error IMHO. Even doctors offices are moving towards EMR or electronic medical records due to human error. To assume that humans have less errors than computers is absurd.

I do know how to use a sextant and ded/dead reckoning and plotting yet, unless it's pea-soup fog, I don't normally pre-plot on paper. I'm a firm believer that one should know old school first, as a back up, but lets face it most new boaters won't ever learn this stuff and unfortunately a chart plotter is the next safest alternative to real seamanship.

I've been in situations, racing in fog, where there were three very seasoned, old school, ded reckoning type sailors, not including myself, all disagreeing upon our position each one insisting they were right. One loose halyard in a race, in thick fog, and all bets are off and positions get lost. So who was right? Since I was not the tactician I was unsure as were the other two. Fortunatley I had thrown my Garmin GPS Map 176 in my bag and pulled up our posiion in less that 30 seconds while the other guys were still arguing about how close we were to Half Way Rock! None of them had been right and the closest one, the tactician, had us off by over a half mile! He had looked at the wrong tide table when calculating drift! This is also a guy who has done Marion to Bermuda as a tactician so he was no spring chicken and a very competent sailor, it happens! In this situation it was human error times three!!! GPS error zero!

In 12 years of using a GPS, aboard a boat, I have had no situation, even in the days of SA, where I could not get a fix. Sure I've had times where my accuracy was more than 100 feet off but I can't draw a line on a chart, with a sharp pencil, 100 feet wide so that really is not a major concern.

To answer your question a chart plotter overlays your actual lat/long positionon a chart. If the charts were bad when they were made, like many Bahamas charts, then the GPS will still show you where you are but the chart is wrong so you could still hit bottom. Relying solely on paper charts is no safer in many areas than relying on any other form of navigation because many charts are just plain inaccurate and no matter howmuc you spend on a plotter it can't correct for poor data!

I know of no less than 30 uncharted rocks along the Maine coast, many them reported years ago yet no charts show them. if these charts are scanned into a GPS and used those rocks still won't show up!
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Last edited by Maine Sail; 03-09-2007 at 12:34 PM.
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  #12  
Old 03-09-2007
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TB...sorry if I wasn't clear in my post. the yeoman plotting board requires input from a GPS to be properly set up to use on each paper chart you put on the board. Didn't know if you knew that so provided the link. Either with an electronic chartplotter or the Yeoman plotting board..you are ultimately relying on a GPS position fix. Now on to more important things:

But most of our navigating while sailing is done from the aft helm, where our 2nd plotter is located. Paper charts would be very inconvenient to use back there.

Are you saying you are sailing relying solely on a chartplotter for your position?? Do you not want your paper charts at your side? I understand you are using them for planning but I cannot imagine not using them while underway as well.
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Old 03-09-2007
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Reading what you guys have written, It's all coming back to me now why I never fitted one in the Aircraft! I remember getting a rush out of Having to establish position when in doubt because of airspace restrictions etc. Doing things theb hard way was actually part of the fun. When GPS came out, you'd meet the village idiot flying around Europe,when previously he wouldn't make it past the tea bar door. But like I said earlier, The boot's on the other foot and I am now the 'village idiot' perhaps the difference is I will use manual navigation even though I'll have a GPS in every locker and enough Duracell batteries to power a Fridge Freezer!

I saw a mention of self scanned Raster charts.
I found this programme which does that and provides lat long positioning from sextant sightings too. I have yet to learn how to use one though but it looks fun and a useful backup to my sackful of GPS devices/battery packs
http://www.tecepe.com.br/nav/
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Old 03-09-2007
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Cam,
I use paper charts for all our planned trips - have been for decades. As a result of years of plotting courses directly on paper charts and repeating the same routes over and over within our cruising range each season, these routes have become permanently penciled onto each chart - and we have amassed quite a collection.

We of course have GPS, in addition to separate but integrated chartplotter screens at both helms, plus a handheld backup. The paper charts are always out on the chart table and accessed frequently when either sailing from the aft cockpit helm or piloting from the pilothouse.

Here's a view of the pilothouse while in Block Island last season:



But having paper charts open on the aft deck is inconvenient during heavy weather and high winds. My point was, if we were to use the Yeoman device from the aft helm, the charts would be even more vulnerable.
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Last edited by TrueBlue; 03-09-2007 at 12:56 PM.
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Old 03-09-2007
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Ahh...ok...didn't sound like the usual TB ! Sorry for the misinterpertation.
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Old 05-17-2007
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Virtual VOR/DME

Just as an add on to the thread. I went on a sailing refresher course recently and was taken aback by the amount of time that people were taking finding position on a paper chart using lat longs from a gps. Particularly in view of the fact that the approx position was known. Time spent below was counter productive in a very busy shipping area I thought.

Coming from an aviation background, It occurred to me that whilst flying along at 130 kts I never had time to bugger around with lat longs and always used VOR/DME. What this system comprises of is a ground station (they are everywhere) that sends out 360 signals so you can always work out which spoke you are on from the compass rose on the map. DME is another signal that shows your distance from the station in miles. therefore you can now see where you are on the map very accurately.

Whilst in the cockpit on the sailing course I decided to make use of a virtual VOR on my marine chart. Of course they are there already. there are compass roses on all charts usually with the lat long shown. All you need to do is programme in chart compass rose as a waypoint on your handheld GPS, then with folded chart in hand, you can see where you are using a straight edge scaled with distance for your chart (if you use a scale distance ruler, you need to watch the scales of the charts of course)

At any time, the gps will give you distance and bearing to your compass rose and you can see where you are.

Is this too simple and should I climb back in my cockpit, or is this idea of any use to anyone . Aviation shops sell those stick on compass roses so you can position them over any suitable waypoint and use the straight edge on that.
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Old 05-17-2007
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Quote:
Originally Posted by Tubsmacker
Virtual VOR/DME

Just as an add on to the thread. I went on a sailing refresher course recently and was taken aback by the amount of time that people were taking finding position on a paper chart using lat longs from a gps. Particularly in view of the fact that the approx position was known. Time spent below was counter productive in a very busy shipping area I thought.
Tubs,
It appears as though you are throwing stones at an acceptable and encouraged method of safe and practicle navigation aboard a vessel? Evidentially you never lost your electrics whilst flying in controled airspace which can and does happen aboard a sailing vessel. The paper charts are a reference tool to the last known position and if taken every 30 minutes will provide a beginning point for dead reckoning if needed. "I rekon I'm dead right". This is not the forum for a replacement for a navigational class but there are many boat saftey classes available. Get into one for your own good, and maybe mine.
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Rick,
I think you misinterpreted my post, You are of course completely wrong in that I'm throwing stones at an acceptable practice. What i was saying was, if things are busy, plotting a gps position using lat long versus quick referencing using the chart compass rose. I never said anything about NOT using DR as a backup. That means you can have an accurate position easily whilst maintaining the position like the one in your photo above

Cheers
Tubs

I am familiar with DR and use it plus I have had total electrical failure that you describe. I had a backup and I used it!
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Old 05-17-2007
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Quote:
Originally Posted by ambianceack
what are the differences and similiarities between a gps and chartplotter?
A GPS receiver and a Chartplotter use the United States buillt and maintained GPS Satelite system orbiting the earth. This stuff seems like voodo majic when it is studied and is absolutely awesome in its development and implementation. You are wise indeed to be considering its possible value to you. Those that thumb their noses to it's value are no different then those that refuse modern medical techniques due to their religious beliefs. Too bad, so sad.
  • Similiarities
    1.Both receive signals from orbiting satelites
    2.Both need power to operate
    3.Both are in a protective plastic enclosure
    4.Both have a data screen that provides user feedback
    5.Both have many different models available
    6.Both are WASS capable
  • Differences
    1.Chartplotter is normally fixed in position. GPS receiver is normally handheld.
    2.Chartplotter has a larger screen useful for using data to show real time position on a chart, GPS receiver displays raw numerical data.
    3.Chartplotter software may be used on an onboard computer to enhance navigational information and is bad to the bone, whereas a handheld GPS receiver can be droped into a pocket when abandoning ship, or can be taken along on a hike, bike ride or whatever.
    4.Electrical denmands on a chartplotter are greater then a handheld GPS receiver.

I use both types aboard as each serves it's own purpose. As long as you are considering a GPS receiver/Chartplotter why not consider a DSC VHF radio?

Got more questions? Look into a United States Power and Sail Squadron Electronics Course. The course is free, a nomial charge for the books.
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Quote:
Originally Posted by Tubsmacker
Rick,
I think you misinterpreted my post, You are of course completely wrong in that I'm throwing stones at an acceptable practice. What i was saying was, if things are busy, plotting a gps position using lat long versus quick referencing using the chart compass rose. I never said anything about NOT using DR as a backup. That means you can have an accurate position easily whilst maintaining the position like the one in your photo above

Cheers
Tubs

I am familiar with DR and use it plus I have had total electrical failure that you describe. I had a backup and I used it!
Tubs,
Whew, glad to read this! Was it the timing of the chart plotting that you were taken back by during the sailing refresher class?
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