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ECDIS systems offer great flexibility in the way chart data is displayed. Chart data or ENC cell data can be presented in a variety of ways according to the requirements of the mariner. It should be noted that there is always a risk of data misinterpretation unless the correct information is displayed.
It is essential to understand the different representations and settings performed by the system - those done automatically and those done manually. The following pages provide an overview of the automatic and manual settings.
The information will provide an overview of ECDIS and its operating system. It will not offer instruction concerning vessel navigation - training of that kind is available through nautical colleges or universities.
Proper voyage planning and good back-up management
Although navigating a small boat Karen's and Jeff's experiences with a total black-out of their navigational equipment and the usefulness of a workable back-up system documented in their Blog is worthwhile to read and I would like to invite all to do so.
Each ENC has its own identifier and the identifier has 8 characters. The first 2 characters indicate the producing country. The 3rd character designates the navigational purpose (see Usage Bands), the remaining 5 characters are unique to and are defined by ENC producing company.
Chart Agents will supply ENC data to vessels in coded form, in accordance with IHO-Standard S-63.
The standard defines code and decode modes for ENC products and the data supplier, and may be downloaded gratis from the IHO website. The code guarantees the authenticity and integrity of the data.
The data will be usually delivered on a CD-ROM.
Some Hydrographic Offices offer their data for direct download.
RENCs offer the possibility to download their ENCs directly via the Internet. To use this new feature an ESIG type approved ECDIS unit is essential.
ECDIS functions - recommended standard settings
The layout of the ECDIS menu display may differ according to the manufacturer's philosophy. It is recommended to specify the following values for some standard settings.
|Display Category||Standard Display|
|Selected sea area||around own ship with an appropriate look ahead distance|
|Orientation||True motion/ North-up|
|Manual updates||if available|
|Operator's note||if available|
|Position sensor||GNSS (Satellite receiver)|
|Selected Route||recent active route with route parameters|
|Look-ahead time||6 min|
ECDIS Content settings
Presentation of the chart content
Mariners have the option to choose between three pre-defined different presentations of ENC content. Individual variations between presentations are possible.
However, it is not possible to reduce the content level below the Display Base (the mandatory minimum content level).
Traffic routeing systems
Orientation and display mode
Units of depth and height
Own Ship safety contours
Indication of isolated dangers
which lie within the safe waters
Display base content
Fixed and floating aids to navigation
Boundaries of fairways
Visual and radar conspicuous targets
Prohibited and restricted areas
Chart scale boundaries
Indication of cautionary notes
All Other Information
Standard display content
Submarine cables and pipelines
Details of all isolated dangers
Details of aids to navigation
Contents of cautionary notes
ENC edition dates
Mariners may choose between the traditional or the simplified presentation of the chart content.
According to the lastest information, the display of simplified symbols will not be continued with the new S-101 standard. The IHO reacts herewith on request given by ECDIS users.
Use of SCAMIN
Depending on the usage bands selected an ENC will display varying levels of data. The ENC scale used can vary from the best possible to a very small scale. When using a small scale, mariners may not wish to display all the object data available for an ENC. Under the S-57 Standard provision is made for adding a special attribute called SCAMIN (Scale Minimum) to a feature object (see S-57 Standard). This attribute can only be defined and provided by the ENC producing agency (usually a hydrographic office or an authorised agency). Once defined, the value of SCAMIN determines the display scale below which these objects will no longer be displayed, and this may have a significant effect on the presentation of ENC data.
Some spatial objects may not be included within SCAMIN, these are:
- Objects covering the earth's surface (e.g. coastlines),
- Objects used for presentation of the Display Base,
- Meta objects that ensure consistency of ENC information.
SCAMIN is a powerful tool and mariners should be aware that they could significantly reduce the amount of information displayed by applying the SCAMIN function on the ECDIS. With SCAMIN applied caution should be exercised.
Source: NOAA cell US5NY1CM.000
Problems of different SCAMIN use at adjacent ENCs
The SCAMIN determination for spatial objects which are basically allowed to carry those characteristics, are not harmonised internationally. Few ENC producers undertake so called SCAMIN drafts and assign SCAMIN values very carefully. Other ENC producers do not it at all, or not sufficiently.
SCAMIN values are provided for certain depth contour lines at the western ENC in the example below. The eastern ENC does not carry any SCAMIN information. By setting different scales, you can see how the display changes. The example is based on real ENCs and is some years old. It was only selected to represent the problem. For that reason all geographic names have been intentionally obscured.
Different employment of SCAMIN values leads to misinterpretation and mistrust especially with adjacent ENCs.
Anyhow, alarms and indications will be still generated according to the defined ship's parameter.
Sources: PT324206 and ES200044
Problems with different interpretations of the SCAMIN values
The example below shows the same cable with different SCAMIN values in adjacent ENCs. The northern ENC has a SCAMIN value which suppresses the display of the cable and the southern ENC has a SCAMIN value which allows the display of the cable.
A chart extract introduced on an EU Project has been used for this example.
T-Kartor developed a tool which compares selected features of adjacent ENCs in identical Usage Bands and displays the disparities.
The work to resolve the disparities must be done by the responsible ENC producer.
Colour Settings will depend on light levels on the vessel's bridge. Mariners can choose between different colour settings. The colours vary from maximum brightness for daylight use (Day bright) and minimum brightness for night use (Night), with three alternative settings between the maximum and minimum.
Source: NOAA Cell US4NY13M.000
Own ship presentation
When increasing the ENC scale, presentation of Own Ship will change from a double circle with an arrow to a defined symbol or shape. The S-52 Standard stipulates that the mariner should be allowed to select whether Own Ship is displayed in true scale or as a symbol or shape, and that the selection may be made manually or automatically.
Own Ship presented in true scale on the largest scale display gives the possibility of high navigational accuracy when transiting small rivers and river bends; also for narrow channels e.g. docks, locks or bridges.
Alarms and Indicators
For ECDIS Systems the IMO publication (Code on Alarms and Indicators. IMO-867E) applies. In accordance with this Code:
means an alarm or alarm system which activates an audible signal, or a combination of audible and visual signals, indicating that a condition exists requiring attention by the user.
means a visual display which provides information concerning the condition of a system or piece of equipment.
The following items should be detected by an ECDIS system automatically. When detected, an alarm and an indicating display should be activated.
- Traffic separation zone
- Traffic routeing scheme crossing or roundabout
- Traffic routeing scheme precautionary area
- Two-way traffic route
- Deepwater route
- Recommended route
- Inshore traffic zone
- Restricted area
- Cautionary area
- Offshore production area
- Offshore windfarm
- Areas to be Avoided
- Military practice area
- Seaplane landing area
- Submarine transit lane
- Ice area
- Fishing ground
- Fishing prohibited area
- Pipeline area
- Cable area
- Anchorage area
- Anchoring prohibited area
- Dumping ground
- Spoil ground
- Dredged area
- Cargo transhipment area
- Incineration area
- Specially protected areas
Alarms or indications should be activated for the following:
- "Largest Scale For" alarm
- Off-Track alarm
- Crossing safety contour
- Deviation from route
- Positioning system failure
- Approaching a critical point
- Change of geodetic datum
Alarm and/or Indicator
- Area with special conditions applying
- Malfunction of ECDIS
- Information over-scale
- Larger scale ENC available
- Different reference system
- Route planning across safety contour
- Route planning across specified area
- System test failure
Anti Grounding function
The image presents different water depth limitations when navigating with an ENC in ECDIS. Mariners can set an advance time warning to indicate when the vessel is approaching the set limits. The following limits can be set:
The depth defined by the mariner, e.g. the ship's draft plus underkeel clearance, to be used by the ECDIS to emphasize soundings on the display equal to or less than this value.
The contour related to the own ship selected by the mariner from the contours provided for in the SENC, to be used by ECDIS to distinguish on the display between the safe and the unsafe water, and for generating anti-grounding alarm.
If an ENC does not offer a depth for the selected water depth, the next deeper option will be selected instead.
Incorrect Deep Contour and Shallow Contour settings may cause problems with alarms based on those settings. Additionally, the chart presentation of the ECDIS system is in that case insufficient.
Following settings are defined to generate an appropriate alarm and a most convenient chart presentation.
Draught: 12 m
Deep Contour: 25 m
Safety Contour: 15 m
Shallow Water: 10 m
ECDIS could be used solely for the chart display. This use will regress the advantages of the system. Rather, ECDIS is most efficiently used when all available ancillary systems and data are linked to it. This provides the mariner with convenient, detailed and accurate navigational information.
It should be remembered that some systems may have to be specially configured to work with ECDIS and that such configurations should be periodically checked.
Examples of systems to be used in conjunction with ECDIS which underline the advantages of an ECDIS are:
ECDIS includes all well known navigational functions, as well as special features that make the mariner's life easier. ECDIS performance runs from the simplest navigational functions through to the recording of voyage data which cannot be manipulated.
On the assumption that most well trained mariners will be aware of how the following functions are displayed, no pictorial representation will be given here.
All conventional functions:
- Fixing own ship's position on the chart
- Drawing of bearing lines and distance rings
- Laying down the intended chart course
- Manual entry of notes
Route planning functions:
- Use of straight and curved segments
Adjusting a planned route by:
- Adding waypoints to a route
- Removing waypoints from a route
- Changing the position of a waypoint
- Changing the order of the waypoints on a route
- Plan an alternate route in addition to the selected route
- Specification of a deviation limit from the planned route at which activation of an automatic off-track alarm occurs
Route monitoring functions:
- Display the selected route and own ship's position whenever the display covers that area
- If in a sea area without the ship on the display, monitoring functions should nevertheless be activated
- Display an alternative route in addition to the selected route which is clearly distinguishable from other routes
- Possibility of modifying the selected route or changing an alternative route
- Possibility of displaying time-labels along ship's track manually on demand and automatically, at selected intervals between 1 and 20 minutes
- Store and be able to reproduce minimum elements required to reconstruct the navigation, and verify the official database used during the previous 12 hours, and the voyage track
- Record at 1 minute intervals:
- Own ship's past track
- Official data used:
- ENC source
- ENC edition
- cell and update history
Ensure that recorded data manipulation is not possible
- Integration of environmental data
- Monitoring function
- Advisory navigational functions.
North-up or Course-up Orientation
ECDIS systems offer two different options for own ship orientation; North-up or Course-up.
IMO Performance Standard takes into account that most anti-collision calculations work better when using a North-up orientation and thus a single control for switching over from Course-up to North-up must be provided.
Presentation of Radar/ARPA Data
The presentation of hydrographic and traffic information on one screen is one of the great advantages when navigating with ECDIS. Briefly the advantages are:
- All data for navigating in difficult situations is available at any time,
- The GPS/DGPS position can be checked by radar image,
- Differences of reference systems and sensor data can be detected,
- Radar echoes can be better identified,
- Anomalies with floating aids to navigation (e.g. buoys in strong currents or adrift) can be easily detected,
- Radar specific limitations can be compensated for to some degree,
- Transfer of Radar bearings and distances on a sea chart becomes superfluous and human error can be limited.
Overlaying hydrographic data with Radar/ARPA information can produce problems. These are:
- Sea clutter,
- Information overflow,
- Mutual coverage of information,
- Priority of presented data,
- System failure e.g. "black out" will affect two navigation systems,
- If ARPA only targets displayed then all other Radar targets will be suppressed.
The ECDIS performance standard requires that Radar/ARPA data does not affect the ECDIS presentation.
Presentation of AIS Data in ECDIS
AIS data can be presented in different ways. Users can choose between simple presentation of main target information or the presentation of all data available.
AIS targets will be displayed, according to their status, in different ways.
AIS information will appear on an ECDIS screen but no further assistance about AIS or its effect on navigation is given here.
Please consult the IALA website in case of further interest.
AIS data transmission
The IMO AIS carriage requirement for AIS units divided between not carriage required and carriage required vessels. The information given below is related to the latter group of vessels.
According to IMO AIS carriage requirement following data will be broadcast:
- Radio Call Sign and Name of ship
- MMSI number
- IMO ships identification number
- Dimensions of ship - to nearest meter
- Type of ship
- Location of reference point for position reports
- Position of the vessel
- Time stamp in UTC when information was generated
- Course over ground
- Speed over ground
- Navigation status (e.g. under way using engine, at anchor)
- Rate of turn
Voyage specific information
- Type of cargo
- Destination and ETA
- Route planning (at Master's discretion)
- Air draught (optional)
Security Message (abbreviated version)
Presentation of AIS data on an ECDIS display
The following screenshots were kindly provided by Maritime School Warnemünde and Scandlines ferry boat "Prins Joachim", Chiefmate Jan Barsoe.
Over-reliance on AIS
For all of you who are thinking AIS is the Swiss knife for safe navigation, collision avoidance and observation of the surrounding sea area it is suggested to consult the paper discussing those issues early 2008.
Navigating with ECDIS
Navigation with ECDIS does not differ significantly from navigation with paper sea charts. ECDIS does not exempt mariners from conducting proper route planning.
I do not intend to give the full, officially required, steps for route planning. However, I have collected, what I think are, the most important points to be taken into consideration.
The voyage planning should consist of:
- Consultation of nautical publications;
- Checking meteorological data;
- If applicable, consultation of meteorological route advice;
- Consideration of routeing measures;
- Consideration of ship reporting systems and vessel traffic services;
- Consideration of which pilotage services are available;
- Consultation of port information;
- Collection of information on shore based rescue facilities and
- The interaction between ship's type, cargo and potential route.
For creating a route, the mariner should consider:
- As a first step, the start and end point of a route;
- Selection of convenient course alteration points;
- The required width of the track;
- The cross track error (XTE) that can be permitted at different stages;
- The maximum allowed difference off track from the planned route;
- The assignment of route parts to great circle or rhumb line track;
- The maximum allowed distance off track and
- The radius of turn and for course alterations.
The following further points should be considered:
- Safety speed;
- Speed reductions to enable difficult passages by day, to catch tide windows and to make use of tidal streams;
- Underkeel clearance;
- Engine maintenance on high sea (we are thinking of cleaning the funnel exhaust uptakes);
- Turning circle and manoeuvre details;
- Routine position fixing with the use of all available position fixing systems;
- Environmental protection and
- Security precautions against incidents (human life, ship, cargo).
Once at sea, mariners should consider at least following points:
- Routine checks of the navigational equipment;
- ETA at each course alteration point and at each other point significant for the entire voyage;
- Meteorological conditions and the traffic situation.
My friend David Acland, an experienced former Royal Navy officer, added some further points which should be mentioned and which require Mariner's attention:
- Fuel usage and bunkering;
- Fresh and drinking water planning if needed;
- Harbours of refuge;
- Alternate ports for contingency;
- Sunrise, Sunset, nautical Twilight;
- Expected time of landfalls;
- Action on failure to make a landfall;
- Clock time checks;
- Zone times ashore and
- When to change ships time.
Certain in-built automatic checking functions for voyage planning, approving and executing provided by ECDIS are described by the figures provided.
The voyage planning combines route planning and time planning.
Route planning can start when the port of destination is received. The route is created from scratch; or waypoint coordinates are entered; or a whole route is imported from another system; or adapted from a previous route.
The result is a route plan table.
Each waypoint can by added by an individual notice displayed on that point.
The required cross track error can be individually set for each part of the route. The example provided shows the effect to the route display if the XTE was set to 50 m.
The route check will be performed soon after the route has been created. The route check declares a route as useful for the current ship's condition when no warnings or risks appear. Routes should be rechecked whenever the route is adjusted.
The result of that check depends on predefined ship's parameter like XTE.
Further warnings/alarms may appear during the execution of the route. They depend on ship's parameters as well. The officer on watch (OOW) is responsible for the correct handling of those warnings/alarms and he should consider the action required. Ignoring warnings/alarms is definitely not an option.
In the example provided the safety depth was changed. That must not be the correct solution. Probably the correction of the route or a part of the route has to be taken into consideration.
Once classified as useful for the ship the voyage can start. According to IMO Performance Standard the selected route and possible alternative routes should differ significantly. A modification of the selected route or the change to the alternative route should always be possible.
Keep always in mind: "The checked route is only useful for the ship, but not for all situations."
After passing WP2 the system generates WP 3 (yellow highlighted) as the new destination for that segment of the whole route.
The watchdog generates an alarm when approaching a danger. It is time to do something
Please do not be surprised about the course steered. It was necessary to activate the watchdog alarm. Otherwise the voyage becomes rather "boring".
We steer hard port now to avoid a collision with the buoys. The automatic log book makes an entry at 0600 and provides the appropriate chart entry.
Since we have just avoided the collision with the buoys we set up the course and steer to WP 3 now.
WP 3 gets a notice which is being displayed afterwards.
It is decided to set 500 m as off track error for the last part of the route. The watchdog shows an alarm.
ECDIS is able to show the reason of that alarm. In this case the ship approaches a depth area. For convenient the position of each issue in the message box is displayed.
As stated before, ignoring those warnings is definitely the wrong way. It is better to solve the problem.
Use of different chart formats
Quit often different chart types are used in ECDIS systems, e.g. Raster Charts. The constraints when using both chart types for the various segments of a voyage and the considerations to be taken are described in the Vector/Raster part of ECDIS basics.
ECDIS with integrated decision assistance services
ECDIS manufacturers are integrating more and more decision assistance tools into ECDIS to increase the possibilities their system offers.
For years the Man over Board function has been the only tool of that type but now it is accompanied by other decision assistance tools.
The following examples provide a first view on such new features.
Man over Board Function
An important tool is the "Man over Board" functionality. ok, some people might say "Person over Board". I am old, I prefer to old way.
Anyhow, depending on the SAR situation the OOW needs to decide between different search methods. Three of those are described with ECDIS relevant details and an associated diagram below.
Each method requires different parameters. The system will not generate a search method proposal if the parameters value is not in line with his respective ship's maneouvre parameter.
Following screen shots and details are published with kind permission of TRANSAS.
Expaning Square Method
The Expanding Square search method requires following parametres:
- Search pattern heading - search direction;
- Turn radius - turn radius between the route legs;
- Number of legs - number of successive route legs;
- Starting leg length - start leg length.
Parallel Track line search method
Parallel Track line search method requires following parametres:
- Search pattern heading - search direction;
- Turn radius - turn radius between the route legs;
- Number of legs - number of successive route legs;
- Leg length - length of each leg;
- Track spacing - width of zone between the parallel tracks.
Sector Search Method
The Sector Search method requires following parametres:
- Search pattern heading - search direction;
- Turn radius - turn radius between the route legs;
- Number of sectors - number of sectors;
- Search radius - search area radius (sectors);
- Turn angle - sector turn angle.
Collision Avoidance Assistance
There has been a long standing desire to provide collision warning or an alarm of a potential close quarters situation.
The new tool automatically analyses all RADAR and AIS visible targets and provides advice to avoid the danger. These could include change of course, or visual or sound signals to other ships.
The "Course To Steer" proposal is based on analysis of the position, course and speed of all ships in close proximity and computes CPA and TCPA with own ship. Dangerous or risky courses are indicated in red on the displayed pop-up, safe courses in blue.
The specified own ship's parameter can be changed either by the OOW or exclusively by the master.
The OOW can change inter alia:
- the alert radius;
- the CPA.
The master can change inter alia:
- minimum value for action to be taken to avoid collision (alerting if ships are approaching from Port side);
- ship's parameter;
- specific ship's parameter.
The calculation is made on default values if no change is made.
Following screen shots are published with kind permission of © Totem Plus.
Piracy activities update
Piracy activities are displayed graphically by this tool. The information is updated daily. Piracy information is combined with current weather information to allow the ship's crew to plan a route with the lowest risk of piracy attacks.
This tool underlines the options ECDIS offers. Information provided from different sources is collected and analyzed to offer important decision assistance.
The following screen shots and presentations are published with the kind permission of © Jeppesen (A Boeing Company).
Ship's Log Book in ECDIS
ECDIS has the facility to record and save voyage data. The ECDIS performance standard requires the following:
- Store and be able to reproduce certain minimum elements required to reconstruct the navigation, the vessel's track and verify the official database used during the previous 12 hours
Additionally, the following data should be recorded at 1 minute intervals:
- Own ship's past track containing
- Official data used
- ENC source
- Update history.
Once stored, the system must safeguard the integrity of the stored information and prevent any subsequent manipulation of the data.