753 - 04/11 - Reporting of ECDIS anomalies - Worldwide

懒猴航海

The UK Maritime authority, the Marine and Coastguard agency (MCA)has issued a Marine Information Notice, MIN, regarding the reporting ofanomalies identified within ECDIS. This sits very well alongside theClub’s own advice identifying possible areas of difficulty to implementECDIS systems onboard, overcoming those areas and avoiding potentialclaims.


Re MCA MIN 406 (M+F): Reporting Operation Anomalies Identified Within ECDIS

With respect to ECDIS, the Introduction to MIN 406 states:
“AnECDIS anomaly is an unexpected or unintended behaviour of an ECDISwhich may affect the use of the equipment or navigational decisions bythe user. Examples include, but are not limited to:
•    A failure to display a navigational feature correctly;
•    A failure to alarm correctly;
•    A failure to manage a number of alarms correctly.
Annex1 contains UKHO NAVAREA1 Warning 317/10 which gives further informationon anomalies and the means to overcome the issues raised.”


MIN 406 Annex 1
3.3 The following is the text from the latest NAVAREA1 Warning 317/10 issued on 290525 UTC Oct 2010:

3.4As previously notified by NAVAREA warning, mariners using ECDIS arereminded not to rely solely on automated voyage planning and monitoringchecks and alarms. Some ECDIS appear only to undertake route checkfunctions on larger scale ENCs and therefore alarms might not activate.This may not be clearly indicated on the ECDIS display. Mariners shouldalways undertake careful visual inspection of the entire planned routeusing the ‘other / all’ display mode to confirm that it, and anydeviations from it, is clear of dangers  
Recent preliminaryinvestigation indicates that some ECDIS may not display certaincombinations of chart features and attributes correctly and on rareoccasions may fail to display a navigationally significant feature.This appears to be caused by anomalous behaviour in some ECDISsoftware, especially early versions. The existence of such anomalieshighlights the importance of maintaining ECDIS software to ensure thatoperational capability and reliability are maintained. It isrecommended that appropriate checks are made with the equipmentmanufacturer.1 This is of particular importance where ECDIS is the onlysource of chart information available to the mariner.
TheInternational Hydrographic Organization (IHO) is investigating thesematters in consultation with ECDIS equipment manufacturers. Furtherinformation will be made available through Notices to Mariners andwithin the UK element of the README.TXT file included on ENC servicemedia.

One major manufacturer  has included the following data on one of their subsequent update CDs:

Use of ECDIS
1.   A very small proportion of shoal soundings, especially those marked as“reported” on paper charts, are not visible when operating in thedefault base or standard display modes and do not trigger automaticgrounding alarms in route checking or monitoring modes. Most ENCproducers, including the UKHO, have now amended the way in which theseparticular shoal soundings have been encoded in S-57  to resolve thisissue.   

2.    Some ECDIS may not activate alarms for all landareas shown on ENCs, even where these are surrounded by a shoal depthcontour. Whilst land areas such as islands are generally clearlyidentifiable on ECDIS, in some display configurations small islands canbe difficult to see as they may be obscured by other detail such ascontour labels.  This is most likely to be a problem where only verysmall scale (usage band 1 and 2) ENCs are available. There are manyoceanic areas for which the largest scale chart (both paper and ENC)issued is 1:3,500,000.

3.    It has been noted that on someECDIS, some underwater obstruction hazards only display in “full /other” display mode rather than in default standard mode as might beexpected. The observed anomalies reinforce the need for the continuedapplication of established navigation principles and skills includingthe need to avoid over-reliance on a single system. Mariners shouldalways undertake careful visual inspection of the entire planned routeusing the “other / all” display mode to confirm that it, and anydeviations from it, is clear of dangers.


Overlapping cells in the same usage band:
Somedata providers issue ENCs which contain overlapping data coverage, bothinternally and with an adjoining nation’s coverage. This may make themdifficult to use in certain ECDIS systems which default to displayingboth overlapping cells. Caution should therefore be exercised whenusing such overlapping data. Mariners should be aware that there willbe a possibility that items of significance may be present only in onedata set within an area of overlap. They should therefore take care toexamine both data sets when planning a voyage through such an area.Some overlaps may be quite small and may not be noticeable when viewingdata at the appropriate scale. Discussions are in hand between many ofthe data producers in order to resolve overlapping data problems.

ENCs derived from charts on non-WGS84 compatible datum’s:
Positionsobtained from Global Navigation Satellite Systems, such as GPS, arenormally referred to WGS84 datum. In many parts of the world however,charts were originally produced on a variety of local datums for whichthe shift to WGS84 may be unknown or unreliable. ENCs derived from suchcharts may not be accurately referred to WGS84 datum. This can resultin small but noticeable positional differences where adjoining cellshave been shifted by slightly different amounts.

A number of GB(Great Britain) cells for example, are derived from charts that cannotbe accurately referred to WGS84 datum. The differences betweensatellite-derived positions and positions on these cells cannot beaccurately determined; the estimated values of the differences forthese cells are detailed in the Information attribute of Caution Areasthus: "Positions in this region lie within ± nn metres of WGS84 Datum".Mariners are warned that these differences MAY BE SIGNIFICANT TONAVIGATION and are therefore advised to confirm GPS positions shown inthe chart display using alternative navigational techniques,particularly when closing the shore or navigating in the vicinity ofdangers. Such cells contain a warning encoded as the name of a Sea Areafeature covering the cell thus: "This chart cannot be accuratelyreferenced to WGS84 Datum; see caution message". They are intended foruse with this warning continuously displayed and should not be usedotherwise.

Updating of ENCs in line with paper charts:
TheUKHO's weekly updating service for ENCs includes the latest updatesissued by all the contributing Hydrographic Offices. These updates mayor may not be synchronised with Notices to Mariners and New Editionsproduced for their national paper chart series. In some cases,therefore, ENCs may be less up to date than the corresponding paperchart of the same area. Practice also varies between differentHydrographic Offices with regard to the updating of ENCs for Temporary(T) and Preliminary (P) Notices to Mariners. Several ENC producersinclude T&P NMs in their cells wherever possible, but where this isnot the case mariners are advised to consult relevant T&P NMspublished in Notices to Mariners bulletins or on the ENC producer'swebsite (if available).

The attributes Date Start (DATSTA) andDate End (DATEND) are used by UKHO and some other Hydrographic Officesto notify mariners in advance of major changes such as the introductionof new or amended routeing measures. The purpose of these attributes isto allow mariners to preview forthcoming changes and for the ECDIS toapply the changes automatically at the appropriate time. ECDIS approvedto IEC 61174 Edition 2 (2002) or later should be able to display thetime-related features correctly. However, ECDIS approved prior to IEC61174 Edition 2 may display both old and new routeing measuressimultaneously or fail to give any indication of the changes.

Chart display content:
Marinersshould be aware that the appearance and content of the data displayedin electronic charts may differ substantially from the same or similardata in paper chart form. The ECDIS chart display is generated"on-the-fly" according to display rules defined by the IHO PresentationLibrary. The amount of detail that is displayed will depend on a numberof factors, including:

•    The cells loaded on the ECDIS and available for display;
•    The feature content of those cells (including any objects with date, time or scale dependent attributes);
•    The display scale set by the ECDIS user;
•    The display mode set by the ECDIS user (i.e. "Base", "Standard" or "All");
•    The Safety Contour, Safety Depth and Safety Height set by the ECDIS user;
•   Other user display options provided by the ECDIS (e.g. options to showisolated dangers in shallow waters, full length light sectors, etc);
•    The ECDIS manufacturer's implementation of the IHO Presentation Library.

Overlay content
TheAdmiralty Information Overlay contains all Admiralty Temporary &Preliminary Notices to Mariners (T&P NMs) and provides additionalpreliminary information that is specific to ENCs, such as reportednavigational hazards that are not yet charted.

The Overlay givesseafarers an easy way to view the information they need, in addition tothe standard chart, to navigate safely and compliantly. The Overlaymakes passage planning simpler and safer by clearly showing whereimportant Temporary or Preliminary changes may impact a voyage. It alsogives seafarers the same consistent picture of the maritime environmenton their ECDIS as they have always had with the Admiralty paper chart.The Overlay includes all Admiralty T&P NMs in force worldwide andadditional information that relates specifically to ENCs, published asENC Preliminary NMs (EP NMs).

The UKHO includes information inthe Overlay where it exists in the UKHO archive of hydrographicinformation. Some ENCs produced by national Hydrographic Offices arethe equivalent to their local paper chart series and there is noequivalent Admiralty paper chart. In these areas the UKHO does not haveany additional information and the Overlay shows a “No Overlay”feature. Additional information, such as local ‘Temporary &Preliminary, Notice to Mariners’ (T&P, NMs), may be available inthese areas from other sources and seafarers should ensure that allappropriate sources of information have been consulted.

Overlay availability
TheAdmiralty Information Overlay is available, free of additional charge,to all users of AVCS and the Admiralty ECDIS who have compatibledisplay equipment (see below).  Please contact your Admiralty ChartAgent to add the Overlay to your AVCS or Admiralty ECDIS Servicelicence.

Although ECDIS has been in use at sea for some years,its employment is not yet widespread and many mariners remainunpractised in its use. Mariners must therefore be aware of the usertraining requirement. They should satisfy themselves that their ECDISprovides all the navigational functionality that they will need andthat they are familiar with the operation of this functionality. Forexample, some early ECDIS systems may be unable to display thecautionary notes which appear on the paper chart and are included inthe ENC. Hence, care is required while experience is gained in thepractical use of ECDIS. Some national maritime administrations haveissued advice relating to the introduction of ECDIS, and marinersshould ensure that they are aware of, and conversant with, that advice.