Is your chart relying on an 1860 survey?

Footnote to cruising the Scillies: piloting there is a reminder of the importance of proper Admiralty charts, because they show the age of the surveys on which they are based, unlike any of the proprietary ‘vector’ charts available on chartplotters.

The Scillies is a mixed area from this point of view. Some of the surveys of the area were last done in 1860 – 1904 by lead line, probably from boats carried on naval survey ships and rowed up and down in straight lines quite a long way apart, so rocks could easily be missed. Other parts of the islands were surveyed at a range of different dates in the 20th century.

The little diagram showing which area of the Scillies was surveyed when is very instructive, and is a warning that in certain places extra care is needed. Interestingly, one small but vital area, the ferry route in and out of Hugh Town, was surveyed in 2012-14, by the Duchy of Cornwall, the landowners. At least we should be able to rely on that route.

This does not mean you have to stick with paper. We would have spent at least £5,000 in recent years if we had bought all paper charts for our cruises. UKHO (in other words Admiralty) charts for the whole of the UK and Ireland, complete with all the supplementary information, can be bought as a single package for very reasonable prices online from the Cowes firm visitmyharbour.com, and combined with the excellent Marine Navigator chartplotting app they make a fine tablet chartplotter as backup to the main system. What you are looking at then is a computer image of an official UKHO chart (technically, a raster rather than a vector electronic chart). In fact, the UKHO charts are now printed from electronic files anyway, so it is exactly the same image.

The popular yacht chart systems such as Navionics, Garmin and C-Map, leave out vital information such as survey age. They are not images of official charts but combine the data in their own proprietary way. They also contain potential traps because they are organised in layers, and as you click from one to another you get more or less detail. If you are on the wrong level you may miss something important. To have the UKHO charts as backup on a tablet is reassuring.

Furthermore, we have seen a number of examples over the years where Navionics has missed out features altogether or got information wrong. There was one example in Tean Sound, where Navionics showed one power cable crossing the sound under water. The UKHO chart, and to its credit C-Map, showed all four.

Chart errors (contd).

Several earlier posts covered inaccuracies in charts. Last week I came across yet another example in Cala de Portinax, a bay at the north end of Ibiza in the Balearics. This screen shot from my Navionics chart shows depths in a fair amount of detail: yet the numbers were wrong by a factor of three or four. IMG_2586 Because of the modest depths shown, we motored in with great trepidation in Olivia Jane, a Beneteau 43 with a 2 metre draft. Yet we found the depths in the middle of the bay were all in the 11-13 metre range and even close in to the rocky shore we anchored in 8 metres. In contrast, the C-Map chart on the cockpit plotter gave no depths at all inside the bay, which is a safer option than mistaken information. We’ve fed this back to Navionics and await a reply, but the nagging question will always remain in future, even if this proves to be a rare mistake: can we trust the inshore information on these charts? What if the mistake had been the other way, showing 11 metres when only 2 metres was there? Do other brands of charts have similar errors? Previous posts on this subject were mainly about errors arising from old surveys; many of these were to do with 19th century measurements of longitude, which become glaringly obvious with GPS. This Navionics chart seems in contrast to suffer from a basic data problem. I’ll update when Navionics replies.

May 14  Here is part of the Navionics reply – they put it right but there is no indication of the frequency of the problem.

Thank you for bringing this issue to our Cartography Department. Navionics appreciates your input and we are pleased to inform you the issue has been corrected. The updated data is currently available for Navionics Mobile by updating your maps.  We have asked to write us from the App, in order to know which App version you were using and you need to update it. Always make sure you are running the most current version of the mobile app. 

However, when I went on line, the app told me that no updates were available at this time. Are the above lines just their formula for telling people to go away? The chart of the bay is unchanged.

11 June
finally got the problem of the Navionics chart errors sorted, with help from the company by email. I deleted and reinstalled the whole app and succeeded in getting the updated version, which matched the plotter and our own depth measurements.

Lessons:
(1) one could go on for a long time not knowing that the charts are failing to notify updates via the App Store. So best to ask it regularly to update and if it keeps saying no updates available get in touch with Navionics help, or simply delete and reinstall (after logging on and syncing to avoid losing data). There must be a bug lurking somewhere.

(2) the chart was bought late last year and is still current – so the error was there very recently. There will always be a nagging question in my mind about whether other mistakes are lurking in the charts.

PS Am now looking into why my 2015 edition of Memory Map’s UK charts, which I have on my laptop, does not mark the position of the massive new breakwater at the entrance to Cowes Harbour, my home port. It says in general terms ‘works in progress’ with no position or indication of what. In Navionics’ favour, they show the new breakwater accurately. I have asked Memory Map what the actual cut off date is for its 2015 edition but have had no reply. 

For more on this subject, see:

Med Charter Disaster? Orkney Roulette Marine Survey Accuracy


How to mimic big ship equipment

To cut back seriously on paper charts, the greater vulnerability of equipment on a small craft to accidental damage would have to be taken into account, including lightning strikes. For small boats it is already possible to buy, at a price, extremely robust electronic systems, including waterproof laptops that withstand impacts (costing several thousand pounds), and high capacity lithium battery back-up packs;  small back-up generators have also become cheaper in recent years and can be accommodated on many mid-sized cruising yachts.

At a cost, robust weather and shockproof  electronic navigation with reliable backup systems should therefore be quite close to achievable now on a yacht. Even if we fall well short of the rigorous standards of an ECDIS system, we will not be carrying 100,000 tonnes of crude oil or thousands of containers, so perhaps we can be allowed to be rather less tough on the backup specifications. Similarly with training: new courses may be necessary, but perhaps not the 40 hours plus specified for ECDIS for commercial ship deck officers.

 Here is our current navigation equipment list plus a few items we plan to get. We rely on maximising the number of independent systems, including some which can be isolated from the boat’s electrical and aerial systems ie reversing the current fashion for electronics integration. Whether isolated equipment can be protected enough to see us through a lightning strike is a question that we are still thinking about.

We also try where we can to use portable equipment that we have bought for other purposes, keeping down the boat budget, but we draw back from the high costs of top-end equipment such as water and shockproof computers and screens. Others may have very different and perhaps much better ideas – it would be good to hear them, and especially any thoughts on protection against lightning (we had a strike 12 years ago that burnt out some instruments but not all).

This list is for cruising British and nearby waters.

  • Basic cockpit chart plotter using vector charts.
  • A separate large screen chartplotter at the chart table is a good option. But we have stuck with a standard laptop in an easily removable protective mount. The laptop is plugged into the boat’s 12 V system; two advantages over the plotter are that it is programmable and could be very easily switched to a backup external battery specifically designed for it (see below).
  •   iPhone or similar with Navionics or C-Map charts in a waterproof case, kept fully charged.
  •  An old fashioned stand-alone GPS at the chart table, feeding the DSC radio.
  • An AIT system, with its own GPS, displaying ship positions on the cockpit chartplotter, where it is of most use, but with a USB connection to the laptop in case backup is needed.
  • Radar.

Plus in due course:

  • An iPad or Samsung Galaxy 10 inch screen tablet, with full vector charts and navigation software, with a bracket to hold it at the chart table and a 12V charging lead. With a waterproof case, the tablet could also be used in the cockpit in reasonable weather for a few hours at a time, held in a bracket.
  • Two or more 8 amp hour lithium external batteries, kept full charged, capable of recharging the laptop, the phone and the Samsung if the boat’s electrics fail.
  • If laptops with separate screens improve, a screen mounted (removably) on a bulkhead at the chart table and a keyboard on the chart table connected by bluetooth would be an ideal replacement for the current standard laptop. It would have  the programmability and screen size of PCs and the convenience of tablets, while protecting the screen better than a normal laptop.
  • For those with a big enough boat (not us): a generator and electrical control equipment to feed a spare battery to provide a complete standby power system for emergency lights, radio and navigation equipment.

 With this level of backup, is a yacht safe if it leaves most of its paper charts behind (perhaps keeping just a few small scale charts covering a wide area)? Does it matter that it would be ignoring the legal warnings by using leisure charts in practice as the primary means of navigation?

This partly depends on how seriously we take the inadequacies, as C-Map and others describe their own products, of leisure charts, which is a whole new issue for another article.

Next, an example of paper and electronic chart inaccuracy: Orkney roulette

Paper-free chart tables

The idea of a paperless chart table is usually dismissed out of hand, and the very suggestion makes some old hands fume. But if a 100,000 ton bulk carrier can now be paperless, then it is hard to maintain that it will always be a mad idea for experienced yacht owners.

For a navigator on a yacht as much as on a ship, the advantages of knowing instantly where you are on a chart, and where you are going, are too obvious to dwell on. An old-time merchant navy officer would have spent many hours in junior officer days correcting paper charts. Tony, the retired master mariner with whom we share our boat, had to do exactly that in his early days. Electronics were therefore the answer to a mariner’s prayer: hundreds, indeed thousands, of charts on one machine, with corrections of the whole portfolio available in one simple operation over the internet. Yet even recently there have been published accounts of yacht cruises round Britain urging people to buy full portfolios of paper charts.

For our own round Britain cruising (the second time in the last six years), £3000 would buy fewer than 130 new UKHO charts, compared with the 850 which Memory Map says it incorporates in its UK and Ireland package. Even with a limited paper edition, we would never have a hope of keeping them all up to date unless we devoted weeks in the winter to correcting. If we bought second hand, even if we could find them all, the correction effort would be much greater.  

In contrast, the Memory Map charts on the laptop cost only £50 for the UK 2013 edition, which includes every chart for the British Isles.  Our c-Map charts for NW Europe, including the whole of the British Isles, cost £180 new and just over £100 a time to update, which can be done several times a year, rather more frequently than most sailors I know get round to updating far smaller paper chart portfolios in practice. Navionics on the iPhone (and shortly on a tablet) is even cheaper, and updates automatically.

The result is that for both round Britain cruises we have bought mainly small scale Imray paper charts and very few large scale UKHO ones. We do not yet rely primarily on electronic charts, because we do not have robust enough electrical and electronic backup systems; but in practice, partly for budget and partly because of the ease of correction, we’ve tipped the balance quite a long way away from reliance on paper. Judging by conversations with other leisure sailors, that is rapidly becoming the norm.

So what exactly is it that makes it safe for a modern 100,000 ton ship to go entirely electronic, when yachts are faced with warnings on their chart plotters and electronic charts that they should not be used for primary navigation? The C-Map licence, for example, says “Only up to date official government charts and notices to mariners contain all information needed for the safety of navigation…..Unless otherwise specified by national maritime authorities, the data licensed hereunder is inadequate as a primary means of navigation, and should be used only as a supplement to official government charts and traditional navigation methods.”

The key official conditions for dispensing with paper charts in the commercial world are:

·  The ship must have an Electronic Chart Display and Information System (ECDIS) approved and certified by its flag state, backed up by a second fully independent ECDIS system. For many ships, an ECDIS system is now mandatory, and it will soon be for all. (The “improved positional awareness”, as some professionals put it, far outweighs the risks of going electronic). Ships may back up an ECDIS with paper charts, but a second ECDIS system has the attraction of avoiding the confusion that can arise from trying to keep paper and electronic portfolios simultaneously up to date.

To go paperless, both systems must use  vector electronic charts, not raster electronic charts (which are basically facsimiles of paper charts); the vector charts must be government issued or authorised and reach a very high level of specification and be updated frequently. One of the many mandatory functions is to display chart quality information, an amplified version of the source data diagrams on UKHO charts. Charts sold with the “professional” label for smaller commercial craft and fishing boats do not meet this standard, and neither do leisure charts.

·Navigators must be trained to a high level in the use of the systems.

Superyachts may be able to afford all that today. But is it possible to get close to these strict conditions on a modest-sized cruising yacht?

Next article: ‘how to mimic big ships’