Charts are square, countries aren’t, it’s a problem. There may be a vision of a utopian world where country boundaries are straight and align with a geodetic grid but the reality, as usual, is much messier. The tricky bit is that each national hydrographic office will create ENC cells with bits missing. The political ramifications of drawing a map of someone else's country can be severe. Politicians just don’t like this sort of thing and Google have managed to upset people to a remarkable degree by misplacing the odd line. So the only sensible thing to do is to create chart up to the national boundary and then stop. Of course by safe I mean politically safe. For the mariner it is a pain in the transom akin to sailing off the edge of the world.

This means we end up with multiple ENC cells of the same area at the same compilation scale but from different providers. The reason you might care about this is that you could easily end up with duplicate or similar features from both cells overlaid on each other. Depending on how your chart display software renders this it will probably look a mess, could easily be confusing and might even be dangerous.

Fortunately the good people at the International Hydrographic Office have already thought of a solution to this. Unfortunately it requires a degree of international cooperation and we (I am speaking for the whole human race now) are not very good at that. None the less several countries have been giving it a go following the principles of the Worldwide Electronic Navigational Database or WEND. This is a great idea and would be even better if it worked. I am not saying it won’t work but there is a way to go yet. One small step in the right direction has just been announced by NOAA and the Canadian Hydrographic Service. They have conceded that the boundary between the US and Canada is not straight so they have agreed on using a wrinkly one instead.

ENC cells are often cataloged and managed by the coordinates of the cell corners. This is fine most of the time and implies that the cell is square. However within the cell is a coverage object which really defines the shape of the area covered by the cell data. This can be a polygon of as much complexity as needed. So if two countries cooperate they can arrange the coverage boundaries along the international border, each country then charts its own bit and everyone is happy. The UK and France are a good example of where this works well. What is happening up on the Canadian border seems to be a little different though. They are still dividing up who does what but, see the above diagram, they are not following the border. Instead they are making sure the the cells will fit together properly but Canada is charting some of the US and visa versa. Why are they doing it this way? I have no idea. Please tell me if you can shed any light on this. Pragmatically the reason does not matter too much. The end effect will (should) be a set of ENC cells which join up nicely.

Why is Britain called ‘Great’. I kind of quite like it, but isn’t it a touch odd? Why don’t we do this for other countries? I mean ‘United’ States is ok if a bit functional. But how about going the whole hog such as Marvelous Mexico, Fantastic Canada or Affluent Switzerland? A more serious minded colleague tells me that technically the country is called ‘The United Kingdom of Great Britain and Northern Ireland’ which as country names go has got to be about as long and pretentious as they get. Apparently the ‘Great’ bit was introduced to distinguish it from the, presumably less great, Brittany (which is now part of France). Alternatively ‘Great’ has its origins in 1707 when Britain became greater by incorporating Scotland. None of this has anything to do with Nuno except that we like to say ‘Great British Nuno’ and sort of imply that the ‘great’ bit is somehow connected with the Nuno bit.

Nuno 2.3 with UK charts is now launched. This really is UK and not just GB because these charts go all the way around Ireland. Check out the coverage here. Here’s how it works. When you download the Nuno installer it does not come with any charts at all. So when you run the installer it will ask you whether you want to use the US or the UK chart data sets.

 

• If you want to change your mind you will need to uninstall Nuno and then re-install it.

 

• If you have purchased a license then you should choose the chart set that corresponds to the license.

 

 

 

Installation finished. Fire up Nuno and you will see there are no charts installed. The World Vector Shoreline will be there but that’s about all.

 

Next job is to go to the support pane and hit the Update button in the ‘Chart data updating’ section. This will go an fetch a complete set of charts; either the UK or the US set depending on your choice while installing. This will work even if you are using Nuno in the trial mode.

Fetching the charts may take a while, there are quite a lot of them.

While you are at it you may as well hit Update for the ActiveCaptain data. This is really quite small and won’t take anywhere near as long.

 

Once the clunking and whirring has finished all your data will be up to date and you are ready to go.

Happy sailing. If you get a minute, please tell us what you think about Nuno.

Wouldn’t it be great if you could use Nuno™ for UK waters? Ok, not great for everyone, but pretty good if you happen to be sailing around the UK. So, good news for UK sailors, we’ve got a set of charts for the UK.

After months of intense negotiations with the UK Hydrographic Office we have secured a deal to use ENC charts for UK coastal water. This is the same chart data as would be used by an ECDIS. Now of course Nuno™ is not an ECDIS, if it was then it would be very clunky to use and we’d charge you a fortune. Instead Nuno™ is easy to use and very cost effective. That may sound like vaporous sales talk but consider that this same set of ENC data, 485 cells, would cost you thousands if you bought them for an ECDIS. We are only going to charge you £120 (inc VAT) for all those cells plus the magnificent Nuno™ Navigator application. That has got to count as cost effective.

Here is what the coverage area looks like:

ActiveCaptain has pretty good coverage:

All the usual chart features are there:

The chart data comes with this disclaimer:

"Chart material has been derived in part from data that has been obtained from the United Kingdom Hydrographic office (UKHO). The UKHO does not sponsor or endorse the product and the UKHO and its licensors make no warranties or representations, express or implied, with respect to the product. The UKHO and its licensors have not verified the information within the product or quality assured it. © British Crown Copyright, 2011. All rights reserved.”

Updates will be available every three months or so.

Nuno with UK data will be out in just a week or so. Watch this space.

Here are a couple of thoughts:

1. Most National Hydrographic Offices, and hence the government behind them, make some sort of assurance or even guarantee about the quality of their charts.

2. Electronic (ENC) charts are generally considered to be an improvement over paper charts. It is easier to be more accurate in using them and updating them for example.

Putting these two assertions together you might be tempted to think that the governments can now make and even stronger statement as to the reliability of their chart data. However scratch under the surface a little bit and this notion can come unstuck.

There are some fundamental differences between paper and vector charts; here I am just going to focus on display options. Paper charts don’t really have any, vector charts have lots. With a traditional paper chart the choice as to exactly what goes onto the chart and how it is displayed is determined by a cartographer (chart compiler). So when the chart is published it can come with as assurance about the accuracy of the data and (this is the important point so pay attention) exactly what the chart looks like. Two skippers in completely different vessels with totally different equipment will be looking at exactly the same image.

With ENC charts, the data will be just as accurate but control over the image has been diluted. If we were to compare several different types of chart viewer using the same data, showing the same area at the same scale then chances are that they would show a different image. Sure they would all be similar but sometimes the devil really is in the detail. In fact (I can already hear the pedants) if you were to try and match the display settings on each of these units them you would still find that there were some differences between the images.

The starting point of this problem is that there is too much data to display. There are some 180 different classes of symbol which are arranged into groups. 20 of these groups must always be displayed and 90 are optional. Of the optional groups 51 are normally visible, switched on and the remaining 39 are usually switched off. Ok – so if you are worried about switching something off that you should really be displaying then you might consider simply switching everything on. Here is what it looks like:

On the left is the paper chart and on the right that nasty mess is all the ENC data. These two charts are intended to tell you the same thing so clearly this is sub-optimal. There is too much clutter on the vector display – something will have to go. In fact clutter is possibly the biggest problem with ENC data. So, you need to switch some stuff off – but what? Actually doesn’t it strike you as odd that right out of the box this chart is virtually unusable and so things have to be switched off? When are these things ever going to be switched on and why? How are you going to decide what should be on or off? This is the crunch; there is no easy way. I guess you could read a manual, learn about S52 viewing groups, brush up on cartography and give it a stab but that is actually quite a tall order. It is quite a lot to expect of your average mariner before they can use and electronic chart. It is also a moving target. You may well get the display looking just so but as soon as you start changing scales it can all go a bit pear shaped and if you use charts from a different producer then all bets are off. With paper charts you need to learn what they mean, with ENC you need to first decide what they should look like.

In all probability what you are really going to do is to take some reasonable default values. Fiddle with anything that you can understand and stop once you have a half decent display. This is a quite rational approach and this is one reason why all the ENC displays mentioned above are going to look different. There are many other reasons and these can rapidly get very technical but I hope you are getting the gist of this now. So the chart data may all be reliably accurate in line with the assurances of the Hydrographic Office but that is not going to help if the thing you just hit was not being displayed on the chart.

With Nuno we have taken the fairly pragmatic approach that the skipper is more likely to be interested in the chart as a navigation aid rather than a computer game. To this end we have attempted, to the best of our ten years’ experience in messing with ENC data, to make the chart display just work. There is a lot of clever stuff involving dynamic positioning of symbols, subtle re-scaling, jiggling labels around, changing fonts, adjusting for display scale, merging multiple cells and so on. The end result is a half decent chart display with very little messing around. It is all on the chart, well apart from one switch which we have termed anchoring mode. This enables additional data to be displayed in a way that would be appropriate if you were looking for somewhere to tie up. So this switches sounding, bottom type and some other stuff on. This is a feature in the new version of Nuno and it is coming very soon now.

The last part of the article from Andy about soundings

 

There are a lot of numbers to display in a small space – even on a paper chart 40” wide.

Conventionally, soundings are displayed...

	without thousands separators or units
	with a single decimal digit displaced ½ a line down instead of with a decimal point (if less than about 30 feet)
	with a bar under the number for drying heights, instead of using a minus sign

Units are implied by the chart – in the UK, non-metric charts were black and white and metric charts are colored. Everything is done to try and prevent someone misreading a dangerous depth for a safe one.

Sounding Units in S-57 (ENC)

ENC is one of several chart products based on the S-57 chart standard. Part of the ENC specification is that all depths and heights be specified in metric units (meters).

But the surveys in the US have been done in English units (feet). When a sounding in feet is converted to meters to be stored in the ENC format and is then converted back to feet for display, rounding errors creep in...

Original depth recorded in survey in feet	Stored in ENC in meters (to 1 decimal)	Displayed on chart in feet (to one decimal)
3	0.9	3.0
6	1.8	5.9
9	2.7	8.9
12	3.7	12.1

We could argue that 0.1’ here and there does not make the chart useless, but it does make the chart significantly more crowded with all those decimal digits. In Nuno Navigator, depths from US sourced chart data are rounded to whole feet, on the assumption that the survey was in feet in the first place.

Soundings can also be very crowded – clutter on the chart, particularly when the chart is displayed at a less detailed scale than it was intended for. The ECDIS display standard (ISO 61174) also specifies rather large text and symbols – larger than are needed on a modern LCD display. The standard S-57(ENC) presentation draws sounding values using turtle graphic symbols instead of text – symbols cannot benefit from clear-type etc.

Taking all this together the display of soundings changes from

	to
Orignal S-57(ENC)		Nuno Navigator

At a smaller scale the difference is even more marked

	to
Orignal S-57(ENC)		Nuno Navigator

The Nuno Navigators soundings might be a bit small to read, but the original is too crowded to read and the existence of small text is the clue you need to know that there is something there – all you have to do is zoom in a bit to read it. Everything else about the chart remains intelligible – you can still see the contours clearly for instance.

Highlighting Soundings

The “Properties at Point” display is an important element of an ENC chart. It shows all the detail of the last thing you clicked on and is one of the big advantages of a vector chart.

It is important to know what you actually clicked on.

	We highlight this on the chart. Here, I clicked on a buoy.
	But it didn’t work so well for soundings, which by a quirk of the S-57 design are grouped together. Here I clicked on the 11.5m sounding lop left.
	But, by remembering the depth of the sounding that was actually clicked on, we can now make it work much better