Chartplotters and rockhopping

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The Lowrance 5150 with NauticPath W Europe chart included looks like a really good deal at under £300 but . . .

I have heard that the NauticPath charts do not include many large-scale inshore charts and are better for offhore work than rockhopping.

Which cheap plotter/chart combination would the panel recommend as currently offering best value for money for detailed inshore work?

- W
 
I use C-Map and a Standard Horizon plotter. C-Map have come down in price recently in terms of coverage per £ and have very good detail in most inshore areas. Standard Horizon are competitively priced and my plotter works well, but I wouldn't use GPS based navigation for rock hopping. The GPS position may well be more accurate than the chart in the plotter, which will be derived from traditionally surveyed chart data. Your position might be very accurate but that awash rock might be a few metres out! Close inshore there is no safe substitute for up to date charts combined with Mk1 eyeball, positioning yourself relative to what else is visible, the way the original survey will most likely have been done.

David /forums/images/graemlins/cool.gif
 
You will generally find plotters described as an "aid to navigation" and I would be loath to rock-hop with one alone. In the Swedish archipelago which has more rocks than I've had hot dinners, I've been happy to sail with helm in one hand and a chart in a waterproof case in the other. The fact that I can no longer read a plotter without glasses may influence my choice.
 
I've been using a Nauticpath chart in a Lowrance 3600 for 2 years now. In my experience (which doesn't stretch to other electronic chart types) the Nauticpath is good where it actually has a chart. The trouble is the chart's edges don't go all the way to the edge of the sea: Loch Linnhe stops short of the north end of Lismore, Dunstaffnage marina and Loch Etive are absent and the east end of Loch Sunart isn't there.
But a few weks ago on the south coast of the Ross of Mull, it was spot on. Last weekend round the Garvellachs and E. Dubh Mor & Beg similarly. We were piloting by plotter primarily, though I think David has a good point about eyeballs and surveys.

Derek
 
As a ex surveyor I am concerned about the ability of plotters and othe relectronic devices to display maps and charts at scales which they were never designed to be used at. On shore I have seen engineers designing structures and making critical measurements to a few milimeters on plans only surveyed and drawn to meter accuraccy at best. Similar misuse happens with 'blown up charts'
 
Strongly endorse Kermudgeon's note about using GPS for rock hopping. Visual transits are the only reliable way to deal with those combinations of chart datum errors (which alter as you shift around a chart . . .) and plotting errors for rocks in thinly surveyed areas. If you're talking 100m, of course, not too bad, but anything less . . . and the risks rise.

Cue lots of comments about 'how I found my way in fog into . . . .'
 
"Rockhopping" is a bit like "near miss", I would ponder. One doesn't really want to rock hop, as indeed I have which I can attribute mainly to my own stupidity and the use of a chartplotter.
I have a Standard Horizon 180 with C Map and generally find it excellent. However, I found that the rock to port as you round the little island into Scavaig is plotted 50m or so towards the shore, so relying on the plotter could lead to a grounding in this instance. I found this out, as another boat in Scavaig was able to show me a radar scan overlaid over the CP (also C Map) which revealed this error. I then didn't trust the local accuracy of the CP map and failed to take note of the rock just to the north of the island which indeed was accurately plotted, had too much scope out, drifted over it and settled on to it at 3 in the morning. Luckily no damage other that dented pride. I vowed to stick to eyeball techiques as the main method. I've visited Scavaig a number of times all successfully without at CP!
 
Hi Nick

I would think twice about the Lowrance: I had to replace the external antenna on mine after just over a year
( and typically, out of guarantee and c.£175.00).

I would also agree with what has been said about the Nauticpath, maybe not the best for our part of the world.

Were I buying another plotter package it would not be the Lowrance.

On the subject of rock hopping, my plotter is mounted below, pretty well out of sight from the cockpit. On the way into the anchorage at Lunga (Treshnish) the other day I used Laurence and the chart rather than the Lowrance.

Saw a very nice Albin V at Gometra on Saturday but it wasn't you.

Cheers

Paul
 
Typical, I can't find the chart with the information on it. But, for example, parts of the Channel Islands were last surveyed nearly 100 years ago: sextant, lead line and a rowing boat.

That information is still used on the charts we navigate with today. Some charts show a little map in the corner showing when different bits of the chart were last surveyed. Admiralty Leisure? I don't think the Imray ones do though.

As David and others have said. The GPS will be more acurate than the chart on your table or in the plotter. Transits of course will be spot on.
 
Another source of errors (as far as rockhopping is concerned) is the datum used for the survey, its various transcriptions, and the sometimes amazing implementations of geodetic transformations you may find in plotter software...
 
Why not try the cheapo version?

I don't have a chartplotter and don't feel a strong urge to have one, but we do carry a cheapo out-of-date UKHO/RYA CD ROM (courtesy of a forumite) and a laptop. We have only ever used it once in "real life" which was in very thick fog (not far from your bit, as it happens).

By linking the old Garmin 12 handheld GPS into the USB socket, it does seem uncannily accurate. I'd read some article in YM magazine where some charter skipper was able to "prove" that GPS should not be trusted going in or out of Tinker's Hole on Erraid. Personally, my response is "Baleaux"; as a test I ran the UKHO/RYA CD ROM in that entrance recently and the screen reading was almost identical to the eyeball reading. Maybe about two yards out, but who'd ever want to rely on GPS in such close quarters anyway? Perhaps the UKHO/RYA stuff is better than the proprietary software sold for dedicated chartplotters. You have the laptop, and probably a GPS. Why pay more?

The laptop battery drain will be sufficient to ensure that you don't become over-reliant on it and lose your skills.
 
Re: Why not try the cheapo version?

First, thanks to all who replied but I am not a numpty and don't intend to use a chartplotter to run into rocks . . . and if there aren't large scale charts loaded I won't be zooming in for a clearer picture!

Of course the GPS is going to be more accurate than the chart - it would be somewhat amazing if it wasn't. Most of the charts of the W Coast of Scotland are surprisingly accurate considering the way they were made, but only an idiot would try to (eg) get into Loch Teacus looking at nothing but the plotter. I've watched a friend's Vega sail over land going round the narrow bend in Seil Sound!

Why people think it is better having a paper chart in the cockpit for pilotage rather than an electronic one I am not sure however - and as far as I am concerned the fact that your approximate position on the chart is shown is a big bonus. Of course the pilot book will be in the cockpit and transits etc will be used - but the plotter can be a big help in quickly identifying which lump of rock you are actually looking at.

The other big advantage of the plotter is that once you have found your way into a tricky spot without incident you can follow your trail out and back in again on subsequent occasions.

The Kilmore Quay Vega guys are great plotter fans, and have used theirs to check the accuracy of the charts of their local rock-strewn waters with some interesting results. Coupled with close observation of the echo sounder and Mk1 eyeball I see the plotter as a great aid in exploring those hard to get to places, not as an invitation to disaster.

Steve, thanks for the Garmin recommendation - could you PM me with where to get it at that price? Is it easily viewable in bright sunlight? What bit of kit would you recommend to add AIS?

Ockle, many thanks for the tip on the Lowrance. The Kilmore Quay guys use Lowrance, but I think they have Navionics charts - which make the whole deal very much more expensive. I thought the Nautic Path deal was just too good to be true.

Sgeir, you are getting alarmingly techie in your advancing years . . .

- W
 
I've spent the last 15 years 'rockhopping' here in the Finnish archipeligo and must disagree with those who say a chartplotter is not particularly useful. I've been using some sort of chartplotter for the last couple of years and have found it very useful to confirm your position within a maze of similar islands and rocks in a couple of seconds. Plotting position with a paper chart and GPS or compass bearings or reference from where you last knew you were one minute ago is often worryingly slow. I cannot comment on the accuracy elsewhere but have found it to be perfectly acceptable in these waters.
 
[ QUOTE ]
I've spent the last 15 years 'rockhopping' here in the Finnish archipeligo and must disagree with those who say a chartplotter is not particularly useful. I've been using some sort of chartplotter for the last couple of years and have found it very useful to confirm your position within a maze of similar islands and rocks in a couple of seconds. Plotting position with a paper chart and GPS or compass bearings or reference from where you last knew you were one minute ago is often worryingly slow. I cannot comment on the accuracy elsewhere but have found it to be perfectly acceptable in these waters.


[/ QUOTE ] Thanks for that - my thoughts exactly /forums/images/graemlins/smile.gif
 
Re: Why not try the cheapo version?

I agree with you about the accuracy of the W Scotland charts. For 2 seasons we have been using a Raymarine C120 plotter with radar overlay. It is mounted in the cockpit where it is very usefull for complementing CCC Sailing Directions and eyeball pilotage. I usually turn on the radar to check the accuracy of the chart when close to shore and can easily see if everything corresponds accurately or is shifted 5 or 10 m and in which direction.

The danger for me is that it has a seductive reliability and accuracy that might lull me into going somewhere I would not want to be if it all suddenly failed. We have seen yachts motoring through the middle of the Torran Rocks – I don’t think I would want to be suddenly without plotter in that spot.

The Navionics charts are nice to use and have come down in price considerably. They appear to include all of the Admiralty small scale detail.
 
I have found that a chartplotter visable from the helm is a great aid when things are a little "tight". As others say, not for planning to miss rocks by 2m, but more for retaining general orientation. When there're lots of similar looking rocks about it is very helpful to be able to quickly and clearly see what is behind and what is in front. The temptation, as others have said, is of course to just blindly follow the plotter. Last year, going into Loch Moidart, while I was really struggling to identify and align ML's transits, the plotted track on the machine made it look easy. Similarly in the Sound of Harris is poor vis. three years ago. However... It is IMHO absolutely essential to be fundamentically sceptical, and continually check using whatever other information sources are available: depth, etc., RADAR if you have it - I don't.

I use C-map and have to date been very happy with it: all the detail required anywhere within the charted limits. That is, until the CC this year. I discovered that Dunstaffnage is not represented in any reasonable degree of detail at all. Not a huge problem, but nevertheless it surprised me.
 
Based on an ex-forumite who recc;d the Lowrance 3500C, we bought one with the Nauticpath card. We have found it to be as accurate and as good as many other. There have been comments about marina pontoons not displaying - but let's be honest if you are looking for that level of detail, you won't even find it on most paper charts. This subject is a heavily biased one as people will always quote what they have and often repeat rubbish that others have said. There's also the eyeball fanatic, who forgets that whatever he sees still has to be referenced to whats on a chart - paper or electronic.
Speaking to the ex forumite other day - he mentioned he'd had an experience with navionics that convinced him not to pay out for the supposed extra detail over the nauticpath. The card was simply less detail in the area than his nauticpath and also inaccurate.
The only downside of the later 5150 Lowrance as fas as I see it - the lack of NMEA 2000. But this will be of little concern to average yottie.
 
c-MAP from Jeppesen is it? They say I would have to use a compatible soft ware to the c-MAP CD -- but they dont suggest what that is - sounds a bit tricky ( and expensive?)
 
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