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Old 24-09-2006, 19:39   #1
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Chart plotters??

My wife would like a chart plotter!!
I have been coastal and offshore cruising for 40 years with traditional navigation methods - hand bearing compass, sextant and chronometer etc and am more that content with this but.... my wife wants a chart plotter.
My knowledge of these things is limited to what can be gleaned in 5 minutes from a salesman and I can see that they may have some value but I have a couple of questions please.
(1) I don't see any means of inputting offsets into the plotter. All my paper charts are WGS84, and some have a GPS derived position plotted directly on them, and some require a GPS derived position to be plotted with a correctional offset. Since I presume that electronic charts are derived from paper charts, what happens here in chart plotter world, and in fact how do you know where if offsets are even required? The reason for my concern is that a short time ago, one of my company's ships, a 22,000DWT multi-purpose cargo vessel had a GPS assisted grounding off the Japan coast due to offset error.
(2) How convenient is to work with a small portion of the chart on a small screen? I am imagining the scenario of working on a large scale paper chart, bringing your vessel to anchor in a small bay for example. Although you are concentrating on the small bay, you are still aware of the rest of the chart and any rocks, reefs etc in your immediate area. In chart plotter world you only have displayed the small bay - the rest of the chart is off in electronic never-land. Is this problematic?
(3) If you install the thing in the cockpit, on the steering pedestal for example, can you really see the screen in bright sunlight?
(4) Are they worth the money?

Any assistance greatly appreciated.

Joke & Chris

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Old 24-09-2006, 20:20   #2
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Modern chartplotter offer many useful features and will of course vary from manufacturer to manufacturer. I can only comment on two the Horozon and the Raymarine. One uses CMap and the other Navionics.

One thing which is good, is that the electronic charts are regularly updated.

You can on some units apply manual offsets and some plotters have two independant windows (or linked windows) where you can have charts of different scales so that you can view the big picture and close up. The C and E series has this feature.

If you want to read some excellent commentary about marine electronics and plotters visit this web site:

Ben Ellsion is the go to guy on marine electronics and plays will all the gear out there, tests it compares it, reviews it.. and answers your questions.

Don't listen to someone like me who has experience with one or two plotters.. listen to Ben Ellison.

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Old 24-09-2006, 20:39   #3
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One thing which is good, is that the electronic charts are regularly updated.
So is paper charts I belive.

I have a chart plotter, but no electronic charts in the thing. Yet anyway.

I use it as a fancy GPS instead, bright color screen and all.

Highly recommended: The CP180:

Bought mine for less than $400.00 on the internet. Love it so far as a GPS, but not sure I need any "chart chips" to plug in. ($200.00 for Florida/Bahamas coverage, but that is 8 cases of beer and the paper charts work good and last a long time.)
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Old 24-09-2006, 23:47   #4
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I do like the term "GPS assisted grounding." The admiral is good at sitting in the cabin shouting "the good water is to the left." I can see from the helm that all there is to the left is mud.

There was once, however, she saved me from cutting a corner and missing a mark that was very hard to see.

She took my address and my name
Put my credit to shame
Sunspot Baby, sure had a real good time
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Old 25-09-2006, 06:03   #5
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if you are using the plotter as a nav aid like most people, then dont forget your echosounder. IMHO this is the most neglected bit of nav kit. I like to be able to tie plotter depth into actual depth (taking into account height above chart datum) and use this most of the time to provide more confidence in the data being provided by the GPS.

A hand held GPS has the ability to use different datums in order to be able to work with land mapping as well as maritime charts. The plotters designed as stand alone units are getting vector charts from one of the main chart suppliers (C-Map, Navionics, garmin etc) and these will all be WGS84.

If you are plotting on a laptop using one of the vector charts, then again AFAIK, these are all WGS84. The datum problem can occur when you are using scanned paper charts (i.e. raster), and where these are either old charts, or have not been updated for a long time. Normally these charts will be WGS 72, but can be a more obscure datum. Most PC plotters have the ability to use a different datum, but there is a danger where you are changing from chart to chart, and they have different datums, that you will get confused and apply the wrong correction. I dont much like raster charts anyway!

There is another correction that you need to be aware off, and that is an index error in the plotter itself. This is a correction that allows the plotter to align itself to the chart, and is normally set up by the manufacturer before sale. In my Navman 5500, you can get access to this correction and tweak it. I suspect it may not be accessible as a user control on some systems.
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Old 25-09-2006, 07:04   #6
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CSY Man,
As far as paper charts being updated I assume you are talking about either you updating them yourself (from NTMs) or acquiring charts from a Print on Demand supplier (they would have the latest NTMs applied). As far as I know NOAA seldom issues paper chart updates and the ones you buy from a retailer (e.g., WM) were probably printed years earlier.

The concern you raised about not being able to see the big picture is, IMO, one of the biggest drawbacks of electronic charts, both raster and vector. As you describe, the electronic display essentially takes away your peripheral vision of the chart. You can zoom out, but then you lose detail. With vector charts a lot of significant details are no longer displayed when zoomed out. With raster charts you can view the whole chart but not always at a usefull resolution. This from a guy who navigates solely with electronic charts (my paper charts are safely stored under bunks and shelves).
However, you just can't beat the easy of storage of a large library of electronic charts over the paper equivalents, and the ease of purchase (can be delivered through the mail on CD or memory card or downloaded over the Internet). When purchased new, electronic charts for a given area are almost always less expensive to purchase than the equivalent new paper charts (unless you opt for less coverage).

So I guess my opinion is that a combination of electronic and paper is the preferred solution over exclusively electronic or paper. However, these days I find that I seldom pull out my paper charts.

Having the chart viewable in the cockpit is also one of the big advantages of a electronic chart displays. For them to be viewable in direct sunlight requires a special (high luminesence, I think is the term) monitor. Most chartplotters have such a display and can be viewed even in direct sunlight. They will be more difficult to view in direct sunlight and you may have to get close to them, but they are viewable. Obviously some models are better at this than others.

Are they worth the money. Obviously for me they are, and I went with a relatively high-priced model (Raymarine C120). Since you are very comfortable navigating without one and it appears the initial benefit you will receive is making the wife happy, only you can put a value on that .

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Old 25-09-2006, 12:57   #7
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There has been a lot of discussion lately about the validity of various types of charts. From my perspective, combining my mediocre plotting and the inherent inaccuracies of charts themselves always put me "about here" or it's varient "somewhere left (or right) of there". For me the biggest value of having a plotter on board is that I don't have to go below and get out any rulers or dividers to read it. This is a trade off with paper charts which require no electricity to read but do require large surfaces. Having my chart plotted on a laptop down below accumulates the problems of both electricity and going below but to each his own.

I really like my CP175C and would some day like to compare one side by side with the CP180. I can say that the CP175 is fully readable in sunlight.

Finally if the wife wants one and the price keeps coming down buying one sounds like a given.
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Old 25-09-2006, 16:56   #8
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As far as paper charts being updated I assume you are talking about either you updating them yourself (from NTMs) or acquiring charts from a Print on Demand supplier (they would have the latest NTMs applied). As far as I know NOAA seldom issues paper chart updates and the ones you buy from a retailer (e.g., WM) were probably printed years earlier.
NOAA makes no paper charts any more. The only charts on paper are Print on Demand (from newest data) at a local retailer or 3rd party printed products generally printed on an annual basis. No US charts have been maintained on paper for a VERY long time. They quit doing mass printing only recently as a cost saving measure. The new Print On Demand charts are printed on better paper now and of course current from the date you buy them. NOAA releases updates to individual charts on a daily basis. Only the international ENC electronic formats can accept minor updates.

For a chart plotter I like the Navonics chip charts best. They add a lot of information anf because they are vector you can work with them at any scale you like. Some plotters have more or less features. You use them in many ways like apepr but in other ways they are unlike paper. Being different makes it a learning process. The concept of using charts is no different just the methods you use. Working in different map projections is made easy. Hand plotting is not easy.

Laptop based software allows more of the features you use with paper charts on a bigger screen. If you use a laptop computer then a PC based solution with software is the cheapest and most flexible. I find I don't need all thet much at the helm but prefer to work out all the courses on the laptop. I also transfer maps and routes from the laptop to a PDA sized handeheld that I power from a 12 volt outlet at the helm. It offers a backup device to the computer that really isn't suited for use on deck.

They all reley on GPS as a location source. Using GPS is clearly a science within itself. You can deal with it as a magic box but it can also do more advanced things when properly understood. It's a tool but it's not a navigator.

Paul Blais
s/v Bright Eyes Gozzard 36
37 15.7 N 76 28.9 W
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