What are Limitations of ECDIS?

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Written by Amit Sharma

1) Lack of Global coverage 

Complications in obtaining worldwide chart coverage mainly due to the policy differences between the national Hydrographic authorities.  

The lack of official ENC makes things just worse. Even if a number of Hydrographic Offices have started ambitious programs of ENC production, very few official electronic charts in S-57/3 format are available today. The result is that ECDIS users have to supplement ENC data with non-ENC electronic charts, such as  

  • Commercial databases of electronic charts, produced by organizations other than Hydrographic Offices
  • Electronic charts produced by Hydrographic Offices, not compliant with S-57/3 (e.g. vector charts in formats other than S-57/3, raster charts, etc.).
  • Required the use of the so-called dual-fuel ECDIS: a system fed with both ENC and non-ENC electronic charts.
  • Since the ECDIS operates in non-equivalent mode when using non-ENC charts, S-52 and the IMO Performance Standards  require that these are not mixed with the ENC. Therefore, they must be loaded in the ECDIS into a separate storage area and must remain clearly distinguishable from official charts even after compilation in the SENC. 

2) Problem of Geodetic Datum shifts in unapproved charts 

The issue of geodetic datum shifts is not a concern for ECDIS since all ENCs should be referenced to WGS84, but it does affect paper charts, RNCs and privately produced vector charts. It is therefore very important that shipping companies use only approved RNC charts in areas where ENC is not available.   

The issue arises because the earth is not a perfect sphere. Over the centuries mapmakers have devised local models of the earth’s shape. Because the earth is not a regular shape the accuracy of each datum will vary as you get further from the specific location for which it was defined. Hundreds of different datums exist to define positions; examples are OSGB36, European 1950, Indian, etc. 

Satellite systems require a global datum and GPS positions are based on the World Geodetic System 1984 (WGS-84) which is a model of the entire earth. 

Problems arise when you are receiving positions based on one datum and plotting them on a chart which is based on a different datum.    

3) The Problem of Recurring Costs 

Why do we have to pay for the data at all, given that the organisations collecting the data are government bodies and not private companies? The reason is that the cost of Hydrographic survey is tremendous, and that HOs, typically retrieve only 15-20 per cent of the cost.  

The cost of ENC production for HOs is one of the main stumbling block a sort of  “hump” in the road to global ENC coverage. HOs need funding to get over this hump but  hydrography is not interesting to a politician. The common citizens do not know the importance of shipping,” and therefore politicians aren’t enthused about allocating funding to the maritime sector. 

ARCS British ARCS charts are sold on an annual basis. Each chart costs about USD 25. A ship that typically runs a global run will need to have hundreds of charts, which if multiplied by $ 25 each year is a huge annual recurring expense.  

Given that a paper chart license requires a one off fee with free updates by subscription, while a digital chart also requires a fee for the chart and for the updates and to be renewed every year.

4) Being electronic equipments, if power supply fails ECDIS is useless.

5) Failure of GPS and Gyro Compass will make ECDIS useless.

6) No software for anti-viruses.

RAVI PRAKASH

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About the author

Amit Sharma

Graduated from M.E.R.I. Mumbai (Mumbai University), After a brief sailing founded this website with the idea to bring the maritime education online which must be free and available for all at all times and to find basic solutions that are of extreme importance to a seafarer by our innovative ideas.

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