ECDIS Part 2: Navigating Using ECDIS

June 29th, 2010 by JCB
Posted in Articles, Features, Technical and Training | 1 Comment »

He had bought a large map representing the sea

Without the least vestige of land

And the crew were much pleased when they found it to be

A map they could all understand.

Lewis Carroll

Farewell!                 Photo: JCB

TRAINING:

In part 1, I expressed concerns over the training and in particular the need for any ECDIS user to be fully competent in the particular type of ECDIS placed on board his ship. Whilst such type specific expertise through training is being achieved the top end of the shipping industry, such as cruise liners and large tankers, the evidence is emerging of an alarming lack of comprehension by many officers of, not just their own system but of ECDIS and its functions in general. These are not just personal concerns but reflect those of many Industry observers.

Why is training such an issue?

Currently if you place any navigating officer on a bridge with a set of paper charts, even if they have been supplied by a country whose charting he has never seen before, he will recognise the key features and be able to plan a safe passage for any vessel to which he has been allocated.

This hasn’t happened by accident but is a direct result of the evolution of the paper chart over centuries which has been accompanied by similarly evolving chartwork skills passed on to successive generations of navigators. In contrast to such evolution, within the next eight years, the safety of the worlds’ shipping and coastlines will be dependent upon navigators fully comprehending not just the principles behind vector charting but the particular ECDIS operating system on their ship. As mentioned in part 1, despite an IMO model course being approved by the STCW committee in 1999, this course is not yet mandatory but ship owners / operators are required to train their officers to use ECDIS under their ISM policies. The top ship owners are sending their officers on training courses, based on the IMO model, run by their ECDIS suppliers and since these normally run for five days these officers will have a comprehensive understanding, not just of the principles of ECDIS, but also of their specific equipment. This is the ideal but only covers a minority group and because so many ship owners / operators now use crewing agencies the vast majority aren’t receiving such comprehensive training. The result is that, in order to tick the appropriate ISM box,these officers are being sent on very basic three day courses which can only ever be generic and with, no exam to pass, make no assessment as to an officer’s comprehension of the ECDIS concept or competence in its use.

Detail from a paper chart

An ECDIS “standard” display of the same area. Note the missing anchorage and restricted zone text & detail! The safety contour here has been set at 10m.

Poor training is a fundamental problem because navigating by use of ECDIS requires a completely new approach to chartwork and the adoption of totally new skills. When navigation by use of electronic charts was first muted there was considerable discussion as to how such a system should operate and although mariners preferred the familiarity of a scan of a paper chart into an electronic version of the same it was considered that, if accompanied by a comprehensive re-training programme, a three dimensional “intelligent” charting system could not just enhance safety but also provide a platform for integrating other information technologies into one central navigational console for the navigator. Thus the vector chart was born. So, here we are in 2010 with the technology in place but without the requisite training. The widespread concerns over this situation are valid because in order to navigate effectively using ECDIS a navigator must forget the two dimensional paper chart and navigate using the three dimensions in which the ship actually operates. Unfortunately, in order to avoid overloading the tiny screen, the vector chart hides much essential navigational information away on different “layers” and the navigator is therefore faced with three major problems. Firstly, he needs to know how to tailor his ECDIS to his ship and the intended passage. Secondly he needs to know what information is available within the ECDIS relevant to the intended passage and thirdly, where to find that information, recognise its relevance and effectively apply it. Quite a tall order for an officer who has joined a ship with an ECDIS that he’s never seen before after a 30 hour trip in a mini bus from Poland who’s only had a 45 minute hand over because the officer he’s relieving is going home in the same minibus. Yes, it has happened!!

Setting up the ECDIS

During the installation of an ECDIS, the supplier should have entered fixed vessel data such as the length and beam and also aligned the ship’s position on the ECDIS with the aerial position on the ship. The manoeuvring characteristics of the ship should also have been entered during installation and once set, this information cannot normally be altered by the operator. As the range is zoomed in, the ship position identifier on the chart will change from a spot surrounded by two concentric rings to a scale plan of the vessel so it is essential that this vessel data is correctly entered.

Generally, unless a vessel is spending a long period in port, it is recommended that the EDCIS is left switched on whilst in port because, like any computer a start up from cold can take a considerable time.

Preliminary set up:

Before commencing a passage the navigator must check the ECDIS for the proposed passage, firstly to ensure that the vessel has licenses for all the ENC charts ( called cells) and secondly to ensure that these are up to date with the latest corrections that are supplied, either by CD ROM or via an Internet connection. So, assuming that all the passage licenses are in order and up to date, the first thing that the navigator needs to do is to enter the ship’s draft and air draft and establish the safety contour based on draft and the required Under keel Clearance (UKC). For example, with a vessel of 6m draft the depth contour could be chosen as 8m. However, since most ENC data is supplied with preset contours, typically at 5m intervals the display will default to the next deepest contour which in this case would be 10m. All areas of less than 10m will show as blue and areas deeper than 10 will be displayed as white (see above picture). So as long as the ship remains in the white area, she is, in theory, safe! There are more complex facilities that can be set up if required but that is outside the scope of this article. In addition to the safety contour, this same depth of 8m can be set as the safety depth. In this case, if the navigator sets the ECDIS to display depths then all depths of less than  8m will show in bold type and those deeper than 8 will be a pale grey. This means that a depth of 9m, although within the 10m blue safety contour it will displayed in pale grey text whereas a depth of 7m will be displayed in bold black. The whole safety of the passage is dependent on this information being correct so, if a navigator fails to set this correctly, the scene is set for a disaster! It could be all to easy for a new watchkeeper joining a vessel that arrived in a loading port with a draft of 4m with the safety contour and depth set at 5m to forget to change the draft and depths to the loaded draft, especially if he was unfamiliar with the ECDIS type in use. Such a failure was responsible for the grounding of the CFL Performer in 2008 where the MAIB report states the following: ECDIS was the primary means of navigation, but none of the vessel’s bridge watchkeeping officers had been trained in its use. Consequently, many of the system’s features which could have prevented this accident were not utilised. However, assuming that our officer has fully trained on his ECDIS the next task is to set up a safety domain. IMO specifications require ECDIS to trigger alarms in the following circumstances:

If, within a specified time set by the mariner. the ship will cross the safety contour

If, within a specified time set by the mariner, the ship will cross the boundary of a prohibited area or of a geographical area for which special conditions exist

When the specified cross track limit for deviation from the planned route is exceeded

If continuing on its present course and over a specified time or distance set by the mariner, the ship will pass closer than a user-specified distance from a danger (eg obstruction wreck or rock) that is shallower than the mariner’s contour or an aid-to navigation.

In order for these requirements to be met  the navigator has to input the parameters for both depth and beam clearances and once set, upon checking any passage, ifany hazards are present along the proposed route then alarms will be generated from the relevant chart at the largest available scale whatever scale is being displayed on the screen.

ECDIS manufacturers often meet the requirements by allowing users to specify a safety domain for the vessel, effectively contained by the following parameters:

• In depth, by the safety contour and safety depth
• In forward extent, by the look-ahead time or look-ahead range
• In lateral closeness by a specified distance.

The following diagram which is reproduced courtesy of Dr. Andy Norris clarifies the concept.

Note that the safety domain requires the navigator to input the vessel / voyage specific parameters and so this must be done at this stage. Best practice would seem to dictate that these parameters should be established by the Master.

Setting all of these voyage safety features will require type specific knowledge of the ECDIS, underlining again the importance of specialist training!

The Passage Plan

Once the vessel’s dynamic parameters have been set the passage plan can be created and it is here that the difference between traditional chartwork and ECDIS working become apparent. Used correctly ECDIS planning provides for a safer  passage but if a navigator is lazy,  pressed for time or fatigued etc, then some important information may be overlooked.

Passage planning on an ECDIS requires exactly the same procedures as for a paper chart and the navigator must follow the same “best practice” guidelines as per the Bridge Procedures Guide  but with ECDIS, the process is complicated by the fact that the navigator needs to know what information is already incorporated into the ECDIS and what isn’t and this is where a weakness of ECDIS is exposed. For example if some changes to buoyage have taken place on the intended passage, a navigator using a paper chart will be aware of this because the amended buoyage will be pasted on the chart over the old system and is therefore immediately visible. With ECDIS, as reported in part 1, problems have arisen with synchronising electronic Notices to Mariners  (NtM) updates for ECDIS with the paper equivalent. So on an ECDIS it may not immediately be apparent as to whether or not the changes been included. Because of this anomaly between the printed and electronic versions of NtM’s, mariners are currently being advised to check all routes with the paper NtM’s. Not a good start for ECDIS!!

In addition to checking the NtM’s the navigator still needs to refer to the traditional printed passage planning documents such as tide & current tables, Lists of Lights, sailing directions, NAVTEXT etc. relevant to the proposed passage. To make life easier there are  an increasing number of companies offering electronic versions of these references and the UKHO have recently launched an “e-Navigator” service which provides all the necessary berth to berth ENC chart cells and other services and documentation relevant to the intended passage in a single download. As ECDIS take-up rates accelerate it is certain that all the major suppliers will offer full data packages which will remove the current tedious and error prone task of cross referencing electronic and printed information. However, this additional data can only be provided as an overlay onto the ENC and must be capable of being removed from the screen by means of a single operator action.

Once the navigator has all the relevant documentation to hand, the plan can commence and the first thing to check (that familiarisation again!) is whether waypoints for that passage already exist in the ECDIS database. If so it can be uploaded for re-use and by running an initial check the ECDIS will verify if the plan is safe for the dynamic parameters previously set. As well as alerting the navigator to any parts of the plan that are outside the  safety domain parameters, the ECDIS will also alert the navigator to charted features of relevance on the passage such as traffic separation zones, restricted areas, anchorages etc. How alerts are presented to the navigator are dependent on the manufacturer with the best automatically jumping to the problem area and others providing a simple drop down list.

If there is no existing passage in the ECDIS database then the navigator will have to create one. Waypoint databases are commercially available and some ECDIS manufacturers supply them with the ECDIS but whilst these are useful, it must be remembered that other vessels are likely to be using the same waypoints so a prudent navigator may wish to amend them, especially in areas of high traffic volumes such as the Dover Strait. CNIS at Dover have been frequently amazed to witness many vessels converging onto the same waypoint when plenty of sea room exists in the sea lane and this was identified as a factor by the MAIB investigation into the collision between the Dutch Aquamarine and the Ash, which tragically resulted in one fatality, in 2001.

If no pre-loaded waypoint list exists for the passage then the navigator will have to start from scratch, which isn’t the easiest procedure on an ECDIS. The main problem that traditional mariners find with this is the small screen size which makes it difficult to obtain the outline overview obtained from a small scale paper chart. However, in practice the advantage of the ECDIS is that by putting in the departure and arrival points any obstructions will be identified and the navigator can then move waypoints and re-check the outline route. For longer ocean passages the ECDIS really shines since it can instantaneously offer a great circle or Rhumb line route or a combination of both thus saving much tedious plotting.

Once a viable outline passage has been established it is then essential to check the whole route in detail using the zooming and scrolling facilities. Although this sounds tedious, it is actually easier and less error prone than drawing course lines on a series of passage charts of differing scales. However, it is essential that this process is done with extreme care because, as previously mentioned, many chart features such as submarine cables are hidden on the different layers of the ENC and essential detailed information such as notes pertaining to precautionary areas needs to be accessed and analysed for relevance by means of clicking on the ! symbol to obtain the “pick report” relating to the feature. Yet again, the effectiveness of this plan analysis is dependent upon the navigator being fully familiar with the particular ECDIS manufacturer’s operating system!

This pick report is one of the most essential tasks during planning because there are some confusing new symbols and display anomalies when compared to the paper chart as shown on the following pictures.

What’s this? A hazard of some sort! Dangerous wreck, Rock, underwater rock awash? It could just be depth unknown but the meaning will only de revealed by interrogating it and checking the object information file. Traditional symbols have been replaced by a new symbology by default but if the navigator prefers the  familiar object display it can be set via the menus. The following pictures show the difference.

Simplified symbols.

Traditional symbology.

These are just two examples of many ECDIS features that need to be fully understood to ensure a safe passage. Whilst all the planning is going on the navigator must never forget that he is working on a computer and he should save the plan at regular intervals to avoid totally losing all the detail in the case of a “crash”. Yes, that happens!

Best practice guidelines recommend that planning is undertaken ion the back up ECDIS unit so once the plan has been completed and fully verified it needs to be exported to the primary unit. This is increasingly done via a data link cable between the two systems. Some commentators have expressed concern that the main and back up units are linked together by such a cable maintaining that the two units should be totally independent to avoid any possibility of a virus or Trojan infecting both systems. However, such an arrangement would require the navigator to create two exactly identical plans for each unit which isn’t practically feasible. and transferring data by means of a memory stick or CD ROM would pose the same potential risk of viral infection but I am unaware of any ECDIS units having suffered from such computer viruses. However, many ECDIS run using the Windows platform and can be connected to the Internet, so that factor, coupled with the presence of unsecured CD, DVD and USB drives leads some to valid concerns that it may only be a matter of time before a virus attack happens. One essential factor that mustn’t be overlooked when transferring the voyage plan is that as a result of the primary and back up ECDIS being independent, the vessel specific safety depth and domain parameters must be set on each set independently and a prudent navigator will undertake the final route verification checks on both systems prior to the passage commencing.

Getting Underway

Once the plan has been saved and exported to the main ECDIS unit at the conning position the passage can commence and it is here that the advantages for a well trained bridge team are evident but for less well trained officers, unfamiliar with their ECDIS system, the differences between ECDIS and the traditional paper chart can result in some important features being overlooked. The performance standards require ECDIS units to have three display modes: Base, Standard and full

Base Display: This displays the absolute minimum information considered necessary for navigation such as the coastline, fixed structures and the safety contour. It is not recommended for navigation but some find it useful for de-cluttering the screen when checking ahead on a small scale.

Standard Display: This is the display for normal navigation and it is a requirement that it can be presented at any time by a single operator action. In addition to the information of the base display this mode contains the drying lines, buoys and other navigation marks, prohibited and restricted areas, separation and traffic routing and precautionary  area ( but not the notes!) Despite being the recommended display, this display doesn’t provide the same information as a paper chart with information such as buoy names and characteristics, anchorages, submarine cables etc

Full Display: This contains all the information contained within the ENC but due to the amount of data this mode tends to overload the typical small screens with text overwriting and concealing other objects except on the largest scales and so again isn’t recommended for navigation. Note that even on this full display mode much of the paper chart detail such as precautionary notes can only be accessed by interrogating objects on the chart to display a pick report of the required information.

In practice additional information is added onto the standard display via the ECDIS menu system to the preference of the watchkeeper but how this additional information is accessed and displayed is not standard and is left to the whim of the manufacturers. However, once set, many systems now permit different users to save their preferred display layout.

The fact that important detail isn’t instantly visible represents the key difference between paper charts and ECDIS. Even with comprehensive type specific training this factor represents the most dangerous aspect of navigating by means of ECDIS because whereas historically the navigator has become used to all the necessary information being visible on the paper chart, the vector chart requires the navigator to be inquisitive and interrogate objects and hunt for additional display features in menus and sub menus.

A full display. Note the depths less than 7m highlighted but also note that this display doesn’t show the text detail so information that is readily available can only be accessed by interrogating an object! with such a cluttered display on a small screen it is easy to overlook important navigational information.

On passage

Assuming the standard display is chosen the ECDIS will automatically choose the largest scale chart available and the default display mode is North Up with own ship in the centre and true motion so the ship moves to near the edge of the screen after which it will automatically reset as with true motion radar. Most navigators find this pretty useless so the menu system offers the same variety of tracking options as the radar.  Most users prefer the centre offset relative motion display but some advanced users on the cruise liners are increasingly using offset Head Up displays on both radar and ECDIS meaning that the displays correspond to the visual picture. The heading marker is a fixed line extending to the edge of the screen and again, in the same way as radar, the vector can be set to either GPS tracking or water tracking. GPS tracking is indicated by a double arrow head on the vector and water tracking by a single arrowhead. The route is usually displayed as a solid orange line. The brightness of the screen is adjustable and there are generally three screen display options of day, dusk and night. Additional care must be taken when in the night mode because some features, such as precautionary zones can be very indistinct.

If the ECDIS is part of an integrated system then information from other systems such as radar and AIS can be overlaid on the ECDIS display and this facility can be very useful. In particular the radar image can provide a valuable verification of the accuracy of the GPS input in coastal water in that the radar land image should align with the chart display. However it is recommended that such radar overlay isn’t left on permanently because not only could it mask important data but it also uses additional computing power which may overload the processors.

On normal passages the ECDIS provides an instant visual position check and alarms sound when a waypoint approaches or if the vessel wanders off track outside the pre-set safety domain or approaches a shoal or other charted hazard. One function that an ECDIS cannot currently perform is to integrate live tide data to produce real time depths so whilst the safety contour and depth settings are fine for normal deep water navigation, when the vessel needs to transit a tidal dependent area, such as arises in my own port, then the auto checking of the passage will flag up as being outside the parameters. Third party software can provide tidal data as an overlay and may also include a passage planning tool to calculate tidal windows etc but  such programs cannot interact with the ENC to produce live depth data. Consequently in tidal restricted areas the safety domain alarms will need to be disabled.

It is very easy for a watchkeeper to have unreasonable trust in the ECDIS position, reassuringly displayed on the chart but the verification of position by other means is as essential with ECDIS as with traditional paper chart navigation because if the GPS is in error then the whole ECDIS is rendered inaccurate and for this reason traditional navigation verification techniques must be used and tools to facilitate this are required to be readily available on the primary screen. If the aforementioned radar overlay isn’t available then VRM & EBL functions enable radar ranges and bearings to be transferred and electronic bearing markers permit traditional chartwork to be undertaken using visual bearings.

If a GPS error is identified then the input must be disabled and the ECDIS used as a traditional chart using traditional position fixing techniques but I understand that this is not a user friendly process on many ECDIS units!

Conclusion

ECDIS is a highly complex electronic tool and still in its infancy so it is inevitable that anomalies in the charting will be identified and the training of navigators will lag behind the implementation dates. In part 3 I will be examining some of the problems and accidents that have arisen already along with the vulnerabilities.

The need for ECDIS to be used with extreme caution was highlighted in February when an ENC error was identified resulting in the following emergency NAVTEX alert to be issued

Mariners are advised that ECDIS may not display some isolated shoal depths when operating in “base or standard display” mode. Route planning and monitoring alarms for these shoal depths may not always be activated. To ensure safe navigation and to confirm that a planned route is clear of such dangers, mariners should visually inspect the planned route and any deviations from it using ECDIS configured to display “all data”. The automated voyage planning check function should not be solely relied upon. The International Hydrographic Organisation (IHO) is leading technical action to resolve this matter. Further information will be made available through Notices to Mariners.

Such notices are alarming but in a few years time, as new navigators come through colleges having done all their chartwork exams on ECDIS, the teething problems should have been ironed out and this next generation of officers will be fully familiar with the operational aspects of ECDIS and navigational safety should be enhanced. Already, on cruise liners and other well managed ships ECDIS is being used as intended and the benefits are evident because in addition to the three dimensional safety domain features, when zoomed right in, a good quality ECDIS can be used as a berthing aid.

Visual assessment for swinging in a restricted area is difficult

The ECDIS provides valuable instant and predictive information.   Photos: Nigel Allen

READ PART 3 “ECDIS PROBLEMS”  HERE