As per IMO performance standard Electronic Chart Display and Information System (ECDIS), is a navigational information system which, with adequate back-up arrangements, can be accepted as complying with up-to-date chart required by regulation V/19 and V/27 of the 1974 SOLAS Convention, by displaying selected information from a system electronic navigational chart (SENC) with positional information from navigation sensors to assist the mariner in route planning and route monitoring, and by displaying additional navigation-related information if required.
Types of Charts:
- Electronic Navigational Charts (ENC): It contains all the chart information necessary for safe navigation and may contain supplementary information in addition to that contained in the paper chart. In these charts duty officer can also interrogate information such as safety settings, no go areas, etc. for safety of navigation these charts are also known as Vector Chart.
- System Electronic Navigational Chart (SENC): It is an ENC that is converted by ECDIS into some appropriate format for optimal chart image creation.
- Raster Chart: Raster Charts are scanned image of paper chart which can be use for navigation provided it should be of approved type. Interrogation of additional information is not possible.
Difference between Raster and Vector Charts:
|Raster Chart||Vector Chart|
|Direct copy of paper chart.||Created electronically using software.|
|Interrogation for more information is not possible.||Interrogation for more information is possible|
|Information stored in single layer.||Information stored in multiple layers.|
|Safety depths, arrival alarms etc is not possible.||Safety depths, arrival alarms etc is possible.|
|Same symbols and colour as of a paper chart.||Symbols and colour as per IMO publication.|
|Scale of chart can not be changed.||Scale of chart can be changed.|
|Cheaper and simple to produce.||Expensive and complicated to produce.|
|Memory requirements is higher.||Memory requirement is lower.|
|Information can not be lost.||Loss of Information is possible.|
What are the Advantages of ECDIS over Paper Chart?
- Targets can be easily monitored when AIS picture is overlaid with the ECDIS.
- Passage planning can be done on ECDIS itself and route plan can be saved for future reference.
- Continuous monitoring of ships is possible with respect to its planned track.
- Alarms can be activated. In case the drifting of ship beyond certain limits, when alteration of course is reached, ship enters critical area, etc.
- To monitor the passage various alarms can be set.
- Charts can be updated with the help of CDs.
- User friendly interface, ECDIS is synchronized with various other equipments. It helps the duty officer for quick response.
Types of ECDIS Display
- Base Display: means it is a level of information below which cannot be removed from the display. It is not intended for the safe navigation.
- Standard Display: means it is a level of information which need to be shown when a chart is first display on ECDIS. Information can be modified according to the mariner’s needs.
- All other information: It is displayed individually on demand.
List of Alarms in ECDIS
- Crossing safety contour
- Exceeding XTE limts
- Deviation from routes
- GPS failure
- Approach to a critical point
- ECDIS malfunction
- Different geodetic datum
- Areas with special conditions
Safety settings of ECDIS
- Shallow Contour: This is a line below which vessel will aground. It should be equal to or more than the draft of vessel.
For example suppose a vessel draft is 9 meters and we set 9 meters for Shallow contour in the setting. The contour will be displayed by joining 10 meters depths if 10 meters is not available it will show the next available value. Water between seabed and shallow contour is not navigable.
- Safety Contour: Basically it is a line between safe and unsafe water. Ship’s draft+ Squat (Tap to know what it is) + UKC – Ht of tide. It is the only contour which gives alarm.
For example suppose a vessel draft is 9 meters, Squat experience is 1.2 meters, UKC policy is 10% of the draft and Ht of tide is 0.5 meter then from the above formula we get the value of Safety contour as 10.6 meters, we can take it 11 meters. Now the contour will be set by ECDIS automatically to 15 meters or the next available value.
- Safety depth: Safety depth is Ship’s draft+Squat. It’s main function is to display spot sounding by highlighting it in bold. Usually it is a practice to keep Safety Depth=Safety Contour.
For example suppose a vessel draft is 9 meters and squat experience is 1.6 meters, by using above formula for safety depth the value is 10.6 meters, we can take it as 11. Now in the ECDIS screen all depth below and equal to 11 will be highlighted in bold.
- Deep Contour: This contour varies from user to user some prefer 50 meters and other may prefer 100 meters.
For example you are about to do Ballast Exchange and set Deep Contour as 200 meters now you can clearly distinguish by the colour in which you can do Ballast Exchange.
Normally the contour value are 5, 10, 15, 20, 30…
This is how we will input the value, If vessel’s draft is 9 meters and after complying with UKC policy, required depth is 14:
Shallow Contour: 9 meters
Safety Depth: 14 meters
Safety Contour: 15 meters
Deep Contour: 50 meters
Category Zone Of Confidence (CATZOC)
Their is a strong possibility that the depth given on the chart may not be accurate and can not be relied upon, here CATZOC or Zone Of Confidence comes into play. By using CATZOC we can determine the accuracy of the depth surveyed by Hydrographer.
For example a vessel is in A2 area of depth 30 meters, that means their can be an error of 1m+2% of depth=1.6 meters. Let’s take ship’s draft 10 meters, squat experience 1 meter, UKC policy is 10% of the draft and Ht of tide is 1 meter. Now our required depth is 11 meters, considering error 11+1.6= 12.6 meters. We can take it as 13 meters, now this will be our Safety depth.
Limitations of ECDIS (Electronic Chart Display and Information System)
- If connection between ECDIS and any other equipments fails, then ECDIS may not be of much use.
- Position shiffting is possible if Chart and GPS are using different datum.
- Over reliance on ECDIS, duty officer may over rely on ECDIS.
- When alarms start coming too frequently their is the possibility that duty officer may acknowledge the alarm even without checking it.
- Duty officer may not be familiar with the equipment because of the design, type etc.
Now days Electronic Chart Display and Information System (ECDIS) is the equipment which is helping officers for safe navigation. However it is just an aid to navigation, duty officer should not rely on ECDIS and should be well familiar with the equipment.
If you want to add something or have any doubt let us know in comment section.