ECDIS — A basic introduction

Malcolm Latarche
Malcolm Latarche

12 May 2017

Arguably the most important step in navigation for more than half a century, ECDIS has evolved from a means of displaying charts electronically to the foundation of e-Navigation. For a long time and until it was clear that ECDIS would be made mandatory, there were few manufacturers active in the field targeting commercial ships.

Several of the early systems which had evolved from products for the leisure sector did not meet the initial performance standards for ECDIS and have been discontinued although they can still be used on non-SOLAS vessels if required.

In essence an ECDIS is a computer programmed with appropriate systems to display electronic charts either on the device itself if it is stand alone, or onto a screen in an integrated bridge or navigation system. An ECDIS can be used in two ways – for passage planning and in operational navigation. When both are done by navigators on board, there are benefits to be had but many ECDIS models allow for passage plans to be imported rather than entered in manually.

The idea that a passage plan can be prepared in a shore office and transmitted as a data file is intriguing but can be dangerous if wrong parameters for the ship (draught, beam or length for example) are included and not checked. Some ECDIS models apparently have the ability for a passage plan to be reversed at the touch of a button. A useful feature for some ships on regular routes but highly dangerous if the system cannot make allowances for traffic separation schemes as has happened in some cases.

The role of ECDIS

The prime role of an ECDIS is to display navigational detail. Both paper charts and their modern equivalent are produced using the exact same information. But whereas the former is nothing more than a graphic representation of a defined area with depth contours and hazards marked, either when the chart was produced or added by navigators using information from Notices to Mariners, electronic navigation charts (ENCs) are designed to have an interactive element.

Electronic charts come in two basic types, raster and vector. Both types are drawn or compiled using data from actual surveys and information from authorities concerning aids to navigation, restricted zones, navigational hazards (wrecks or submarine cables for example).

A Raster chart is a scan of a paper chart and as such has the same clear and easy to use style mariners have been accustomed to. What makes navigation with raster charts appealing is that the updating is automated and GPS position can be overlaid to give real time situational awareness.

A vector chart on the other hand is a database that permits a computer generated representation of the chart making use of detailed data that can be further interrogated. Objects on a vector chart can be selected or ‘clicked on’ to reveal further details and the data that is contained within the chart can be accessed by the ECDIS to activate certain features.

For example, the depths and contours on a raster chart are mere inanimate pixels but while the vector chart will show the same figures and lines, if an alarm feature relying on depth is activated, the ECDIS can inform the user of any conflict or danger. Zooming is a highly useful feature of modern computing capability and the ECDIS is no different. However, when zooming a raster chart, every detail will grow larger and more pixelated making it difficult to interpret. By contrast, zooming on a vector chart will simply move the display to a different scale without any pixilation occurring. If zooming out on a vector chart to the smallest scale, some objects and features may become over-written and it may be necessary for the operator to turn off some layers of detailing.

National hydrographic offices are the only official source for chart data for SOLAS and electronic charts produced by official hydrographic offices for use with ECDIS must be vector charts that conform to standards laid down by the International Hydrographic Organization.

The key standard that applies to current ENCs is S-57 which covers the data and S-63 which is an S-57 chart with additional security encryption to deter illegal amendments and pirating of ENCs. ECDIS makers have been obliged to incorporate means of dealing with the encryption in their products.

Raster charts are not considered as complying with SOLAS requirement for ECDIS but there use may be permitted for navigation in areas where no official ENC exists. A raster chart may also qualify as a back-up for an ECDIS.

Although an S-57 ENC is the requirement for SOLAS, manufacturers of ECDIS have devised their own graphics and hardware configurations and the data that is contained within an ENC will need to be converted into a System Electronic Navigation Chart (SENC). Some major distributors of ENCs have developed their own system standards which a number of ECDIS makers have incorporated into their systems. Sometimes ECDIS makers refer to products that can operate with several of these distributors as ‘multi-fuel’ ECDIS.

There are a number of ECDIS makers that distribute the official AVCS dataset in their own internal SENC format, ChartWorld, Navtor and Transas. C-MAP also operates a SENC data service in conjunction with Primar.

These services can in some instances reduce the ENC installation time as the dataset has come in a converted state. The number of OEMs offering this service is low because of the need for a large install base to make the service profitable as each SENC is proprietary. Not all Hydrographic Offices allow their data to be converted to SENC on shore.

S-57 is the current standard for ENC production but the ECDIS makers and the IHO are already looking to the future and a new standard S-100 is in the process of development. S-100 came into force on 1 January 2010 and is the document that explains how the IHO will use and extend the geospatial standards for hydrographic, maritime and related issues. S-100 extends the scope of the existing S-57 Hydrographic Transfer standard.

Unlike S-57, S-100 is inherently more flexible and makes provision for such things as the use of imagery and gridded data types, enhanced metadata and multiple encoding formats. It also provides a more flexible and dynamic maintenance regime via a dedicated on-line registry. S-100 provides the data framework for the development of the next generation of ENC products, as well as other related digital products required by the hydrographic, maritime and GIS communities.

Work has been completed at the IHO on the latest version of the presentation library which is now mandatory for all new systems and will become so for existing models by August 2017. IHO is also working on the new ENC standard S-101, derived using S-100. The International Association of Lighthouse Authorities are using S-100 as the basis for the e-Navigation concepts being developed.

Because the new presentation library will mean that new systems will need to incorporate it and older systems may need upgrading. Buyers of ECDIS systems should satisfy themselves that they are purchasing a system that conforms to the latest requirements.

ECDIS Overlay information

In addition to its basic role as a device for working with electronic charts, the ECDIS can also be used to display additional layers of information. Not all can do this and not all are set up to do it. When navigating it is not unusual for radar, ENC, AIS and other data all to be displayed on a single screen. This permits all information to be visible at all times but not all agree that this is a good thing. A cluttered display can lead to some important information being missed while in the event of a system failure it may take vital time in setting up displays on other screens or on the radar or AIS equipment itself.

However, the ability to overlay information when passage planning can be very useful. Depending on the ECDIS maker it may be possible to overlay information on weather, piracy, ECAs and Notices to Mariners. One service that can do the latter is the UKHO’s Admiralty Information Overlay. Distributed as a free service to subscribers to AVCS the overlay is designed to be displayed on top of a standard ECDIS chart display and can be switched on and off without changing the underlying chart.
As the user zooms in or out, the ECDIS will automatically select charts of a suitable scale and the overlay features relevant to that selected chart. For example, a Temporary NtM that applies only to a large-scale chart will not be displayed when smaller scale charts of the same area are being used.

All Admiralty temporary and permanent NtMs that are in force are included and each is displayed as a simple red polygon (usually rectangular) with red hatched fill which indicates the area affected by the NtM. Each NtM carries the same NtM number that is used in the Notices to Mariners Bulletin. The full text of the NtM is included as an associated text file which can be displayed by selecting the ‘Temporary Notice to Mariners’ or ‘Preliminary Notice to Mariners’ feature in the ECDIS Pick Report. Any associated diagrams can also be viewed through the Pick Report.

C-MAP also has an overlay service for NtMs and its OceanView service allows weather and piracy overlays either on systems on board or in a shore-based office for voyage planning purposes.

There may be a common performance standard for ECDIS but there are very large differences between individual makers’ products and in the way they are intended to be used on board. There will almost certainly be big differences in the level of support and service offered but this will only be learnt from experience.

Using ECDIS will eventually become second nature to navigators but for the time being the range of options is not seen as a good thing in all quarters. As an indication, the foreword to the UK’s MAIB report into the grounding of the chemical tanker Ovit in the Dover Straits in 2013 highlighted the problem saying “This is the third grounding investigated by the MAIB where watchkeepers’ failure to use an ECDIS properly has been identified as one of the causal factors. As this report is published, there are over 30 manufacturers of ECDIS equipment, each with their own designs of user interface, and little evidence that a common approach is developing”.

The ECDIS related accidents referred to were only those investigated by MAIB which means they either involved UK-flagged vessels or happened in British waters. It can safely be assumed that there have probably been many more involving other vessels and in other waters. The report had other comments about ECDIS use and training but while incidents of this type are regrettable, they were not unforeseen.

Almost all modern vessels leave the shipyard with a fully integrated navigation or bridge system in which ECDIS is a vital element. However, now the retrofit part of the rollout programme is in full swing several different types of ECDIS will be required to meet the different standards of bridge facilities. Undoubtedly an ECDIS is most effective when combined with other navigation systems but this will not be possible on every, or even most, retrofit ships.

Here the commonest and cheapest solution will be a simple standalone system that allows compliance but little more than that. It may well be that on some ships the ECDIS will be declared as an aid to navigation and sit unused in the corner of the bridge while navigation on board is practised as it always has with paper charts and little else.

There are more advanced stand-alone console types that can be fed with data from other systems often making use of the fact that the VDR already draws much of the data together and provides a good source to tap in to. In an integrated navigation system with multiple screens it will be possible for even a single ECDIS to be linked to several of them allowing for a high degree of flexibility in workstations.

If an operator decides to settle for a ‘paperless’ bridge and this is allowed by the flag state, then a dual ECDIS system is required under SOLAS. This would naturally suggest a second machine but some manufacturers do provide a dual ECDIS solution in a single console. The backup ECDIS is permitted to have a marginally smaller minimum display size and this may
favour the makers of PC type systems, although it has to be said that most systems on the market do have displays that exceed the minimum size required by a considerable margin.

The requirement for a second ECDIS if paper charts are not carried is to ensure that in the event of a system failure, a backup system will be available. With paper charts onboard, a means of navigation will always be there even should a machine fail but the question has been raised concerning what the legal situation will be if a ship with dual-ECDIS installation has a system failure that would mean only one ECDIS available.

If this occurs at sea, the assumption is that the failed ECDIS will be repaired at the next port of call, but if that is not possible will PSC authorities permit the ship to sail since it is clear that no backup will be available in the event of the second ECDIS also failing? Some have suggested that a third ECDIS will resolve this problem but that is true only if two units do not fail.

Since an ECDIS is nothing more than a specialised computer, the likelihood of systems suffering electronic failure is on par with any other computer system. In an integrated bridge system it is likely that an extra display will always be available thus removing one source of potential failure that exists with stand-alone systems. The matter of virus infection is however a different problem altogether.

Few ECDIS manufacturers offer a wide range of systems although some have recognised the different needs of customers and can offer a system to suit most pockets. In many cases the difference between a basic machine and the most advanced will not be obvious from the outside since the difference is in the software loaded onto the machine or the features activated. These machines make upgrading to a higher level easier and cheaper than might otherwise be the case.

In a small number of cases, the same device might be sold as a radar, a chart radar or an ECDIS with different aspects of the same pre-loaded software being activated. Some ECDIS come with a full catalogue of ENCs preloaded and only require a licence key to be entered for the chart to become available.

For shipowners unsure of what to commit to, there are alternatives to outright purchase. A growing number of makers and some independent service companies are offering a leasing service. Leasing would appear to be an ideal way of equipping a fleet without a high capital outlay and also permits a ‘try before you buy’ approach that will identify the best system to suit an individual operator. Another benefit is that leased equipment can be exchanged for upgraded models as required and can also be swapped in case of a breakdown under the terms of the lease agreement.