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Traditional or simple?

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?





By anonymous | Thu, Oct 2010 03:15 | #

Although there are points to be made in having commonality in symbology, there is are also solid points to be made for the simplified symbology.

First, and foremost a strict reading of the IHO S-52 standard dictates that the sofware should not make assumptions on the behalf of the mariner. Restricting display to the paper chart symbology only, or defaulting to the paper chart symbology puts the design of the software in conflict with a strict interpretation of the written standard.

Second, although I find the following argument somewhat specious and academic in its nature, it can be argued that a simplified symbology could allow for more rapid interpretation of the chart under extremely adverse conditions. Especially, when the ECDIS is part and parcel of the an Integrated Bridge System (IBS).

For the broader markets, though, I am a canditate for  selecting a single, unified set of symbologies. This would,in my opinion, lead to the following: (1) make implementation easier, (2) possibly reduce software development and time-to-market costs for ECDIS vendor,(3) thereby increasing the likelihood of reduced cost to the ECDIS consumer, (4) increasing overall adoption rates of ECDIS systems.
Simon Salter

By Simon Salter | Mon, Oct 2010 11:28 | #

You are quite right that an ECDIS needs to support both symbologies. Nuno is gloriously not an ECDIS which means we feel a bit less constrained in how we implement certain features. In particular we think that we can do a bunch of stuff better than the standard. Simplified symbols are a case in point - we that maybe the world would be a better place without them.
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