ENC supports two types of symbology for buoys and beacons. These two symbol sets are referred to as ‘traditional’ and ‘simplified’.

Traditional symbols look a lot like those you would find on a paper chart. These are internationally agreed and some of them have been in existence for over a hundred years. So they are pretty familiar. They are used on all paper charts and as a consequence on all electronic raster charts. Excellent description of these symbols here.

Simplified symbols appear on ENC vector charts and were invented along with the ECDIS standard. Technically they are described in the S52 standard which dates from sometime prior to 1996 and is currently at edition 6.0 (March 2010). The DNC vector format also has a set of simplified symbols but these are different again.

In comparison the traditional symbols are more pictorial, more detailed and more descriptive than the simplified set. You might have guessed this from the name. An obvious question is why do these exist at all? The paper chart symbols are time server, proven, reliable and readily recognizable by anyone familiar with a chart. The simplified symbols are rendered (drawn on the screen) using just straight lines. This may have been easier to see on the coarse resolution monitors that were typical of 15 years ago.

Here are the symbols for a Lateral starboard hand conical  buoy with a Quick Green light.

Is one of these clearer than the other?

They both convey the same information so why invent a new standard? Actually this is a bit of a trick question because on a paper chart the buoy would be drawn solid black indicating it was green or black. ENC does not use filled symbols so the term ‘traditional’ needs to treated somewhat liberally. Why no fills? I am not sure but I would guess that the reasoning is that it might obscure something important underneath. So why doesn’t this happen on paper charts? Probably because the cartographer (chart compiler) makes sure that everything is drawn just so. It is hard for a computer to be suitably discriminating.

There are 58 traditional symbols but only 38 simplified ones.

So something has to go.

Here is a Pillar buoy with a ball on top. Long flashing white light. The Ball indicates safe water.

The traditional symbol shows you what the buoy looks like. It is a pillar with a ball on top. The simplified symbol just uses a red circle to indicate safe water. Maybe with an electronic chart you also have good positioning and so you are less concerned with visually identifying the actual buoy and more interested in that you are in safe water? Of course you can always inspect the properties of the buoy to find out what shape it is. Whatever the reasoning is I find it is not clear cut and certainly not an obvious justification for learning an additional set of symbols. You are going to need to know the paper chart symbols even if you prefer simplified on your ECS.

So which symbol set is best and why?

It seems to me that if you choose to use the simplified symbols then there should be a clear cut reason as to why they are better. The traditional symbols are familiar. Paper charts are not about to go away. Using a different symbol set means more learning and more chances to get it wrong. Why are there two symbol sets? Most ECDIS/ECS allow a choice for the display. Surely one of these sets is better than the other and that should be the end of it.

So what do you think? I’d really like to hear some opinion as to which you prefer to use and why. Does one set stand out better than the other? The simplified symbols use blocks of color which do not normally appear on a paper charts. So they certainly look different but is that necessarily an improvement? Were the originators of vector charts just showing off? The data is carefully set up so that information about an object and the way an object is drawn are quite separate. If you were so inclined you could create a whole different set of symbols and render the same chart data quite differently. Maybe this feature was so ‘clever’ that they just could not resist using it for something. What do you reckon?

Commercial shipping has a requirement to carry up to date official charts. Traditionally these have been paper charts. Every few weeks a chart agent will visit the vessel bringing new charts and also updating the charts on board. Updating consists of adding pencil annotations, overlaying bits of tracing paper and even pasting on a small, new pieces of chart. This is all tedious and time consuming so it is easy to see the appeal of digital charts and automated updating. However commercial vessels cannot simply switch over the digital charts. The official part of the requirement is important.

After quite a lot of wrangling and discussion between the International Hydrographic Office (IHO), other international ship controlling bodies, various national Hydrographic Offices, chart producers, equipment manufacturers and an assortment of other interested parties some standards emerged. S-57 was designed as a standard for transferring data between hydrographic offices but it got co-opted for sending charts to ships using a product specification called ENC. There are some other S-57 products such as AMLs and AIO but these came later. S-63 was designed as the license enforcement and encryption layer. Unfortunately this was published with errors in it which are still propagating issues today. S-52 was an attempt to decouple the presentation (symbol) for an object from the data representation. This started quite well but then got terribly complicated so that now S-52 is almost like a small programming language in itself. In consideration of the overall system requirements ISO61174 was produced. This describes equipment and software performance standards and is the main standard against which equipment is tested. A navigation system, hardware and software, which complies with all these standards is known as an ECDIS (Electronic Chart Display and Information System). An ECDIS can be used , with some qualifications, on a commercial vessel to satisfy the chart requirement.

Unfortunately the ECDIS standards are quite old. S-57 was frozen in 1996 and ISO61174 dates from 1997. Now old, as such, is not necessarily a bad thing, but these standards prescribe the behavior and performance of computer equipment which had not even been invented at the time. They are standards based on a prediction of what the future would be like. As such they are not a bad guess but are still well short of the mark when it comes to contemporary approaches towards interacting with computers. Nuno Navigator is not an ECDIS. At CherSoft we have developed software for ECDIS. In fact we have quite a long history of this. However in Nuno Navigator we have taken the best features of ECDIS, the bits that actually work, and brought them into a thoroughly modern and genuinely user friendly environment. Nuno Navigator is classified as an ECS (Electronic Charting System) rather than an ECDIS. It is not really intended for commercial vessels.

Globally the whole business of updating charts is in a bit of a mess at the moment and probably will be for a while. Most national hydrographic offices are fairly well set up for maintaining their paper portfolios. This is no great surprise as some of them have been in this business for a century or more. However with the advent of electronic charts a lot of things have to change. The whole production process needs to be reorganized (not cheap) and some of the basic ways of thinking about charts have to change.

Raster charts are commonly produced as facsimiles of the paper charts. In a simplistic system they are literally scanned from the paper originals. This can give rise to inaccuracies for a range of reasons not least of which are distortions in the paper and non-linearity in the scanner. Scanning at a resolution appropriate to the electronic chart can cause a rather jagged appearance which is most noticeable in diagonal lines and known as aliasing. The raster chart has far fewer dots (pixels) than the corresponding paper chart and this can compromise appearance. A better production method is to create the raster image from the same electronic chart images used to drive the paper printing process. There are still some issues here with re-projection which need to be handled correctly but in general this is a cleaner and more accurate process. It also allows image processing such as anti-aliasing which gives a better visual impression when the electronic chart is displayed.

In either production technique the updating of the raster charts follows on more or less naturally from the time served paper chart update process. It is then common for the vector charts to be produced from the raster data, more or less indirectly from the paper chart production mechanism. At the end of the update chain are the third party chart producers who copy the official data sets and repackage them in a variety of ways. Quite naturally these are the last types of charts to get updated.

But this is all changing because this is not a good way to handle vector data and vector data is the future. It is a separate issue as to why vector charts are the future or whether it is the right future but for now it definitely is the future. The IHO and other august bodies are committed to this and substantial funds are being invested. This matters because creating vector data from paper charts is just not a good way of doing things.

In the vector world everything is an ‘object’ like a light or a depth contour or a traffic lane. Each object has ‘attributes’ like the color red or a certain depth. Each object also has a position (the ‘vector’) so it is represented as a point, a line or an area. These objects can be quite readily managed in a simple database but the natural way of organizing them is to tie them more directly to the raw survey data. So when a report is received that a new wreck has been found it is just entered into the database – no intervening chart required.

Vector charts are now a cinch to produce. A cell is just a collection of all the objects in a given geographical area. The problem of actually displaying the chart data is palmed off to the ECDIS or ECS. Paper charts and raster charts are a bit more problematical because the traditional role of the cartographer has been taken out of the loop. Have you ever wondered why a modern chart display simply just does not look as good as a paper chart? Well this is why, there is no longer a cartographer involved to lay out the chart and make it look ‘just so’. Instead we have a dumb computer, and they are all dumb, attempting to reproduce the sort of work that takes a human many years of training and experience. It just doesn’t work so well.

Now to be fair the automated vector to raster production processes are getting better but none the less there is still a complete role reversal. The raster chart becomes a second class citizen to the vector chart and the paper chart ends up at the bottom of the pile. Instead of being the primary focus for updates it becomes the last. There are undoubtedly many advantages with vector charts and with paper charts generated from vector databases. However, for the foreseeable future, they are never going to match the visual quality of the charts that have become standard fare for the mariner for many years.

Last in the chain will always be the third party chart producers. Fortunately as their update feeds become predominantly more electronic (just another output from the database) then these updates should become more timely. Ultimately they should be able to match the official charts for accuracy.

Just now we are in a great transition phase. Some hydrographic offices are pushing ahead with vector only systems while others just deal with traditional paper charts. Most are somewhere in between and possibly a bit unsure of which way to go or how it is all going to shake out. Meanwhile the mariners can look forward to improved electronic charts coverage and more rapid updating. They can also anticipate charts which do not look so good and which, in some cases, are going to cost more. Maybe this is just a classic engineering compromise.