old charts

[roger]

I passed over to another boat (British) an obsolete chart of part of Finland. The chart had been published in 1999. The recipients later comment (with a bottle attached) was that it was more up to date than his electronic chart on his lap top.
Now one reason I had replaced that chart was that I'd frightened myself on one of the inshore passages because of buoyage changes.
My conclusion was that there are probably a lot of very old electronic charts circulating which are not at all fit for rock hopping in Scandinavia though they are probably ok for open water. However in my limited experience most of the routes from deep water to a port in Sweden and Finland are fairly complex. You can wander past the countries but dont close the shore without genuine charts.

<hr width=100% size=1>Roger

 

[MainlySteam]

The official electronic charts will be as reliable as the current paper ones as long as both are corrected. A ship recently went aground off Scandinavia (Norway, if I recall correctly) using non official electronic charts and that was treated as being very naughty - non official (eg not ARCS, Maptech, etc) are not approved for navigation (and often their packaging states words to that effect).

John

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[waverider]

In the North Ionian I used an Imray chart that had a disclaimer stating that it was reliable as the 19th century datum for what thats worth!

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[Sunnyseeker]

My word of caution from bitter experience is.....even new charts can and do have human errors in the printing. We found someone at Imray had put a lighthouse on the wrong headland on the very treacherous North coast of Spain. My electronic chart which was old was correct, we were very confused at the time so approached with caution. the harbour entrance looks like every other cove from the sea but most are full of rocks and breaking seas. If we'd arrived at night with only the Imray and possible tired after a Biscay crossing we could have easily parked up on the rocks in a 5m swell. I'm now much more cautious on new harbours and dont tend to trust any bits of paper!

<hr width=100% size=1>Oh ye who have your eyeballs vexed and tired feast them upon the wideness of the sea

 

[Peppermint]

Re: Scandinavia

suffers from rather to much coastline and rather to small a population. There is not enough dosh to re-survey much of the country. The UK resurveys about 6% of our waters pa. The priority areas are areas subject to movement, so mud not rock.

In Norway, nearly all rock, the result is that much of the survey work is confined to the commercial areas where buoys are moved or channels moved and that many updates or errors in other areas are the result of yotties and fishermen "finding" the changes.

So the idea of an up to date chart is very much pie in the sky. You can have all of the latest chart software or paper you like but if the last time a surveyor passed that way was in 1890 how up to date is that.

User reporting of error and finding is a vital tool of chartmakers so if you find a fault or uncharted feature, log it carefully and report it to the local hydrographer. He'll love you for it.

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[Althorne]

I'm a bit new to gps and use C-map with the gps that came with my boat. Does this mean that I have to update my gps as well as my paper charts and can I do that 'inside the machine' for permanent downloading or do I just do it for whatever courses I put it. Sorry if this seems a bit dim but haven't used it a lot except as a back up to paper charts to try and make sure I don't go too far off course.

<hr width=100% size=1>http://colvicownersclub.mysite.wanadoo-members.co.uk

 

[pandroid]

I agree. I've sailed extensively in Sweden and Denmark with the latest charts, both paper and electronic, and where they are wrong, they are both wrong.

In practice, my 1998 chart packs are fine for 99% of the same area.

I'd reccomend up to date charts for swift moving areas like the UK East Coast, and possibly the Frisians.

Its worth waiting a bit for the Finnish charts as they are only now converting them to INT 1 format, like the rest of the world. They've done the Helsinki pack, but not the rest of em. Incidentally, there's large areas on both the Swedish and Finish charts which are not fully surveyed, and this is reflected in the electronic versions.

The only up to date stuff is the specialist <A target="_blank" HREF=http://www.hydrographica.se>Hydrographica</A> high resolution charts. These are pretty good, but even these have the odd bug.

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[AndrewB]

I agree its nice to have up-to-date charts, but specially for a yacht like ours that carries about 300, its something of a council of perfection.

Even if you do buy new, it isn't always all it seems. I cruised the Bahamas a few years ago with brand-new Admiralty charts, only to realise that the date of surveys on which they were based in some cases went back as far as 1860 (HMS "Thunderer"). This is an area where growing coral reefs can result in just as much change as an east coast sand-bank. True, modern lights and buoys were marked, but it seemed UKHO hadn't caught up on the fact that a hurricane two years previous had taken nearly all of them out.

Despite this, we still got everywhere. Dinged the odd rock perhaps, but not when we weren't expecting we might.

Charts must never be relied on implicity, they are only an AID to navigation.

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[DavidofMersea]

Have I missed something?

I can understand the East Coast, with moving sand, needing to be resurveyed every so often, but why does Scandinavia need resurveying, rocks don't move, do they?

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[roger]

Thanks for the replies. A few points:-
Theres a general problem with chart accuracy. Swedish charts say specifically that GPS postions may be more accurate than their charts.
In Finnish waters we found we had to guess at the datum used. In fact at Mariehamn the Finlands Hyfred (sic) the error was pretty small whreas WGS84 put us onshore. However on the next chart pack going east we met fog at the end of our approach to Jurmo and our track went at least 50 yards north of what I'd intended putting us on a collision course with a very large granite rock. I didnt check to find out if the problem was chart datum or my making a mistake which was sloppy of me. There are time when high accuracy can be important and particularly around Scandinavian coasts.
Obviously if you have electronic charts its wise to get them updated whwnever possible but it will probably cost quite a lot.
Certainly Finland is going through major changes in charting and buoyage. The strain shows in the use on a major waterway of a green can buoy and a pointy port one.
What disturbs me most is the prospect of people wandering about in Scandinavian inshore waters with probably buchshee and ancient electronic charts expecting them to be adequate - they are'nt!

<hr width=100% size=1>Roger

 

[roger]

Re: Have I missed something?

The buoyage and the buoyed routes change

<hr width=100% size=1>Roger

 

[DavidofMersea]

Re: Have I missed something?

I don't understand why? The rocks don't move, do they?

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[[448]]

Re: Have I missed something?

About 3/4 years ago during a cruise up the West coast we decided to to try out the anchorage at Eilean Mor MacCormaig half way up the sound of Jura. This is approached via a narrow "canal" and opens out into a pool with room for maybe two freindly yachts. In the middle of this pool is a dangerous sunken rock. We spent ages trying to locate this rock so as not to anchor near it. Couldn't find it so just anchored anyway with no trouble.
On returning home I related this experience to sailing pals only to be told that the army had blown this rock up the previous year.
Yes, rocks do move!
Cheers, Dave.

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[Peppermint]

Re: Rocks

are removed, channels do change to accomodate different vessels etc.

Rocks are discovered regularly. Survey methods have changed a bit over the centuries and leadline surveys gave a variable density of soundings that missed spot hazards. Some times a wire drag was used if the surveyor thought he was onto something but not always. Echosounders improved the quality of surveys but compared to the new multi beam or even Lads Lidar, which is an airborn method using two colours of laser beam, they were always missing stuff too. So modern surveys find new bits and pieces all the time.

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[waverider]

There are sites by using a search engine.....where you can find updates roger that give lat/longs of hazards in a particular sea area.......I use one for the Greek islands.

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[starboard]

Re.EILEAN MOR

Your dead right the army did blow up the offending rock....however managed to make two smaller ones now for you to hit!!!

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[jenku]

Re: Have I missed something?

They get bigger and bigger as the land raises and the water level drops. The Swedish archipelago also gets shallower all the time. I have some hope of climate change counteracting this, though. And doing away with the bloody ice during the winter, too...

<hr width=100% size=1>http://www.sail.to/alacrity

 

[Birdseye]

Re: Have I missed something?

Whilst GPS has been more accurate than some of the charts, a lot of this error is being picked up as UKHO moves from OSGB to WGS datum. The reason is that many of the sea features on the chart close to shore were traingulated from land - and the land maps themselves werent accurate. This has been corrected up to a point by OS and the UKHO charts are being re-drawn at the same time as being changed to WGS. Its one of the reasons why the process has taken so long and is still not finished for Scotland

The UKHO say that mainly areas used by shipping are re-surveyed in the UK so the 6% a year doesnt mean the whole lot every 16 years. It means the same shipping channels / harbours every few years, and lots of yottie only areas are not surveyed at all.



<hr width=100% size=1>this post is a personal opinion, and you should not base your actions on it.

 

[duncan]

Re: updating C map

the GPS plotter has two elements - GPS being the position fix and, in your case, C Map being the electronic charting. The unit puts them both together to show you where you are.
it follows that the C Map chart will need updating in the same way that paper charts do.
unfortunately most software in the UK will not allow you, the user, to move buoys or add hazards so you need to get a new copy of the electronic chart when available. This is either held on a small cartridge or memory card which you exchange for the new one, or you connect your plotter to a computer to download from a new media source (downloaded file/CD rom etc) - probably the former in your case.
how frequently you change will depend on a number of issues but, as this thread highlights, the nature of your cruising waters is probably the most important. Also note that many electronic charts contain a lot of port information, tides etc that can also go out of date. The fastest changing items tend to be buoyage and sand bars - and there is no guarantee that a new electronic chart will be that up to date anyway! - like charts they are not maintained in real time.
quite frankly unless you are heading into new waters alll the time, with significant channels and buoyage, then you are not going to gain much from updating charts unless the underlying chart upon which the electronic one is based is fundamentally changed; again as illustrated here that might mean a new datum - and that doesn't happen very often.
as a practical example I have a couple of plotters on board but wouldn't dream of updating the charts for buoys for my home waters (Weymouth - Solent) as I probably couldn't even get an absolutely up to date one if I tried! As said the rocks don't move far - unless they are blown up! Poole Harbour entrance may move gradually and the shingle bank off Hurst may well move yards after a blow but so what?
the one area of concern is small shallow channels in harbours, usually marked by withies - for the areas I use a lot (Poole Harbour) I 'survey' them myself at high water and record the best route for the year otherwise I use the withies as everyone else!

I should add that the above comes from someone who uses chartplotters 'way to much' in the opinion of many - however combined with a good sonar and an up to date almanac what more could you want for costal cruising? /forums/images/icons/smile.gif

<hr width=100% size=1>madesco madidum ..../forums/images/icons/smile.gif

 

[ChrisE]

Updating ARCS charts

To me this is one of the strengths of ARCS charts that can be updated using a CD containing the latest corrections weekly, if you like. I do mine once a year on a maintenance contract from the suppliers. I rather like this system as they are the same NtM that would be used to update your Admiralty charts and I have better things to do with my non-sailing time than updating buoys, etc on paper charts.

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