Imagine this. You're caught out by an unexpected gale, with driving rain and building seas. Visibility has dropped to less than a quarter of a mile, and it's getting dark. You're beginning to feel cold and a bit seasick, and your crew are decidedly quiet. Just to make things worse, your chart plotter has developed an intermittent fault.
But no worries. You're only two hours at the most from a safe harbour. The paper chart tells you that you should pick up an east cardinal buoy three miles away that will lead you safely past shallow water and into the buoyed channel between the sandbank and a rocky shoreline, and once past, there's plenty of shelter.
You draw clearing bearings on the chart to keep you away from the nasties, and set course for the east cardinal, distracting the crew from their current miseries by setting lookouts for it. But none of you can spot it.
Your Estimated Position (EP) was checked against your handheld GPS and can't be that far out, so after a bit of tacking you think 'sod it' and head for where you think the buoyed channel should be. You have to be more or less in the right place, but still there are no buoys where you expect them.
You check your handheld GPS again, and your navigation is spot on. You should be right at the approach to the buoyed channel. Suddenly, one of the crew shouts “White water dead ahead!”, and sure enough, just where the channel should be there's a mass of breaking waves - all the indications of shallow water. You're lost. You do the right thing and turn back to sea in a hurry.
Nightmare scenario? You bet. And one that could have been avoided by updating your charts. The sandbank had shifted half a mile to the east, and the buoyed channel had been moved, along with the east cardinal, by the same amount.
It was clearly marked on the latest edition of the chart, but your chart is at least seven years old and has never been corrected. So while your navigation was spot on, you were sill in danger of driving hard on to a sandbank, with disastrous consequences, because you had an old, uncorrected edition of the chart.
Chart correction is something that most yachtsmen intend to do at some point. But it's a vital part of your safety preparations, and needs to be done regularly. You can keep your charts fully up-to-date by using the Admiralty Notices to Mariners (NMs) service.
Admiralty NMs contain all the corrections, alterations and amendments for Admiralty Charts and Publications and are published weekly as booklets. They are also available online, but if you have got behind and need to work back over a number of months, or even years, you can find them all, dating back to 2000, at www.ukho.gov.uk/amd/weeklyNms
NMs are fine if you do corrections every week - as most professional navigators are required to do - but they can potentially apply corrections to every chart published by the UK Hydrographic Office, and many of the notices are temporary in nature - a new wreck being marked before clearance, for example, or the temporary removal of a buoy.
So if you haven't corrected your small collection of charts for a while you have to discard a huge amount of information in order to spot the few corrections that apply to you. The UK Hydrographic Office website provides a more focussed service where you can enter the identification number of your specific chart (provided they are Admiralty charts) to find the corrections that apply to that chart.
You can find it at www.nmwebsearch.com
. Trinity House, the authority responsible for the UK's major lights and buoyage, provides a very useful website which gives the latest NMs in specific sea areas around the UK coast. www.trinityhouse.co.uk
However, before attempting to correct your carts, you need to check that you have the latest editions. Nick Tasker of the UK Hydrographic Office reminded me recently that new editions are published when major changes, such as the recent shifting of the Shingles bank west of the Isle of Wight, are too large be incorporated into the weekly notices.
These new editions can also contain a large number of minor corrections, but most importantly, NM corrections are only applied to the latest edition. So your chart may be six years old and still current, or two years old and out of date.
If you have an out-of-date edition, the best thing to do is to buy a new one. All Admiralty Charts are sold fully corrected, so buying a few new charts at the start of the season may be a good investment not only in safety, but in time as well.
Don't forget that electronic charts also need updating, too, so if you've got a chart plotter it's worth checking the manufacturer's website to see if there's an update to your area.
There are also chart updating services that do the work for you, though these tend to be expensive, and I find that by doing the corrections myself I get to know both the area I'm sailing in, and the chart symbols themselves, a great deal better.
And if you're planning next summer's cruising, there's nothing better than getting to grips with the charts for that area than by doing the corrections.
Richard Thomas holds a Commercially Endorsed RYA Yachtmaster and Cruising Instructor (Sail) certificate. He runs his own delivery business, www.yachtmovers.co.uk
He is available for deliveries, assisted passages, own-yacht tuition, and yacht management.
