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Navigation charts

Updated 11 Oct 2019

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Other than in exceptional circumstances, ships are supposed to navigate using only information supplied by national hydrographic institutions for that specific purpose. Historically, the data was presented on paper navigation charts but although paper charts are still an authorised aid to navigation, most ships today make use of electronic charts displayed on an ECDIS.

Navigation charts are primarily used for passage planning and this is done on the chart table which is commonly placed behind the bridge itself. It is important that the chart relating to the current position of the ship is always on the chart table in case of an emergency as this will allow hazards in the immediate vicinity to be identified and appropriate action taken.

Once they have been produced, paper charts remain valid until a new chart is produced by the relevant hydrographic office. During this time, if they are part of a ship’s folio of charts they must be maintained up to date with information that is published from time to time in Notices to Mariners. As long as this is done, the chart may be several years old before it needs to be replaced.

The situation with ENCs is quite different and, to many peoples’ minds, unnecessarily complicated and expensive. The cost issue was quite controversial in the run-up to making ECDIS mandatory and there is no doubt that installing an ECDIS will add to the costs for ship operators, especially those that opt for maintaining paper charts either as the primary or back-up method of navigating – in some cases being obliged to do so by the flag state. With paper charts and ENCs being approximately equal in price, the result will be a doubling of initial costs.

The greatest criticism that has been levelled at the method of supply of electronic charts is that true ownership does not really pass to the ship operator because the payment is not for the chart itself but a licence to use it for a fixed period. The licence period for ENCs can be three, six, nine or 12 months. Additional chart data may be added to the licence at any point during the licence period and there is no requirement for all data to expire at a common date.

This allows users to hold only the data that is appropriate for their operations at any given time. Some countries do not allow data to be licensed for a shorter period than 12 months. Where shorter licences are available they generally carry a pro-rata price although the rebate is less in some cases.

One thing that can be said in favour of the licensing system is that, for ships operating in the spot charter market, a voyage outside of its normal trading region need not cost as much in charts as would otherwise be the case. Obtaining a licence to use a chart can be done in a variety of ways. On systems where the ECDIS is populated with ENCs bought as and when needed, the licence will be included in the price charged for the ENC which might be supplied by way of digital media, USB or download. On those ECDIS that are delivered with a complete folio of ENCs pre-installed, shipowners may subscribe to a service that either requires them to request a licence for a particular chart in advance or one where the licence is activated the moment the ship sails into the area covered by the ENC.

Once the licence for a chart expires, the chart will continue to display but it will no longer be possible to load and apply updates to it. If the chart is still needed for navigation because the ship must pass through the area covered by it to complete a voyage, this may leave the vessel open to action by PSC inspectors. If this does happen it should be quite simple for the shipowner to purchase a new licence and update the chart within a very short space of time.

It should be noted that much of the data used to produce ENCs is historic and not the result of recent surveys. It is for each national hydrographic office to produce ENCs of its territory but not that of its neighbours even though in some cases this may mean that the display on the ECDIS may be missing features in parts.

The problems that could arise because of this and which could impact on the safety of ECDIS were recognised by the International Hydrographic Organization (IHO) which responded by establishing the Worldwide Electronic Navigational Chart Database (WEND). WEND covers the standards to which charts must be produced and principles of co-operation between hydrographic offices and establishes the concept of a network of Regional Electronic Chart Coordinating Centres (RENCs) that allows members of the IHO to cooperate to resolve overlaps and gaps in coverage.

Each RENC takes over the responsibility in its area for the collation of ENCs and updates for the region and through the exchange of the regional datasets and their updates between all RENCs each RENC can offer an identical global dataset for ECDIS.

It was not intended for the RENCs to become distributors of ENCs to vessels. That role was left for commercial organisations to apply to become value added retailers (VARs) and to develop their own distribution channels in much the same way as Inmarsat services are delivered by service providers. The WEND concept has not been fully adopted by all ENC producing nations and some still insist on distributing their ENCs individually either through chart data suppliers or directly. There are currently two RENCs in existence: Primar and IC-ENC.

Primar is headquartered in Norway and includes the national hydrographic offices in Brazil, Croatia, Denmark, Estonia, Finland, France, Greece, Iran, Latvia, Mozambique, Norway, Poland, Russia and Sweden. IC-ENC has offices in the UK and Australia and its membership comprises Argentina, Australia, Bahrain, Belgium, Brazil, Chile, Colombia, Cuba, Denmark, Ecuador, Germany, Greece, Iceland, Mexico, Mozambique, Netherlands, New Zealand, Pakistan, Peru, Portugal, Romania, Russia, South Africa, Spain, Turkey, United Kingdom, Uruguay and Venezuela.

When an ECDIS is supplied by its manufacturer, some will be delivered with a complete world folio of ENCs, some will come preloaded with ENCs agreed between buyer and seller and some will be devoid of ENCs altogether. It remains the owner’s responsibility to ensure that ENCs for the voyages a ship is undertaking are both licensed for use and up to date.

If the ECDIS has no or insufficient ENCs installed, the owner must obtain them from an authorised distributor appointed by a RENC or national hydrographic office as appropriate. Being only data, an ENC can be delivered by any method of direct transfer (CD, DVD, USB etc) the ECDIS supports or via broadcast download using the ship’s communication system.

Martek Marine’s iECDIS also has an additional option of updating using the GSM networks by way of an integrated modem. There are distributors all over the globe just as there always have been for paper charts, but the very different method of using ENCs has led to a small number of specialist distributors appearing. All distributors can deliver ENCs in S-57or S-63 format for the ECDIS to convert into system electronic navigational chart (SENC) format but some of the major companies will have a proprietary SENC format that certain ECDIS makers have integrated into their systems.

Where an ECDIS maker has preloaded the system with a full or partial folio, the licences still need to be obtained from a distributor. Even when the only charts available were paper charts, SOLAS required ships to have up-to-date official charts on board for their intended voyage.

Updating Charts

Paper charts are updated manually by way of tracings supplied by chart agents and using information contained in Notices to Mariners (NtMs) which are distributed by various flag states and which can be obtained by subscription or by collection from customs and port authority offices. Most port agents maintain a collection of NtMs which they make available to ships consigned to them. With the advent of satellite communications it has become possible to distribute NtMs using broadcast services and e-mail.

ENC updating is a far easier task, only involving installing the update data, which can be provided by CD/DVD, e-mail or broadband. Some ECDIS and some chart providers’ software can recognise which ENCs need updating and perform the update automatically whereas others require intervention from the ECDIS user. It is important when updates are done by ECDIS users to log which updates have been applied.

If a user forgets to update an ENC, it will still display but obviously without the update. This could prove dangerous and could result in a PSC detention. In this respect, ENCs are no different from paper charts. As explained earlier, some advanced ECDIS have additional features such as weather, tidal and even information on latest pirate activity that can be overlaid on the ENC display. These services also rely on broadcast information and often use the same software that manages chart updates to ensure the latest information from these services is being displayed.

ENC graphics and standards

National hydrographic offices are the only official sources for chart data for SOLAS and electronic charts produced by official hydrographic offices for use with ECDIS must be vector charts that conform to standards laid down by the IHO. The key standard that applies to current ENCs is S-57 which covers the data and S-63 which is an S-57 chart with additional security encryption to deter illegal amendments and pirating of ENCs. ECDIS makers have been obliged to incorporate means of dealing with the encryption in their products.

Raster charts are not considered as complying with SOLAS requirement for ECDIS but there use may be permitted for navigation in areas where no official ENC exists. A raster chart may also qualify as a back-up for an ECDIS.

Although an S-57 ENC is the requirement for SOLAS, manufacturers of ECDIS have devised their own graphics and hardware configurations and the data that is contained within an ENC will need to be converted into a System Electronic Navigation Chart (SENC). Some major distributors of ENCs have developed their own system standards which a number of ECDIS makers have incorporated into their systems. Sometimes ECDIS makers refer to products that can operate with several of these distributors as ‘multi-fuel’ ECDIS. There are a number of ECDIS makers that distribute the official AVCS dataset in their own internal SENC format.

These services can in some instances reduce the ENC installation time as the dataset has come in a converted state. The number of OEMs offering this service is low because of the need for a large install base to make the service profitable as each SENC is proprietary.

Not all hydrographic offices allow their data to be converted to SENC on shore. S-57 is the current standard for ENC production but the ECDIS makers and the IHO are already looking to the future and a new standard, S-100, is in the process of development. S-100 came into force on 1 January 2010 and is the document that explains how the IHO will use and extend the geospatial standards for hydrographic, maritime and related issues. S-100 extends the scope of the existing S-57 Hydrographic Transfer standard.

Unlike S-57, S-100 is inherently more flexible and makes provision for such things as the use of imagery and gridded data types, enhanced metadata and multiple encoding formats. It also provides a more flexible and dynamic maintenance regime via a dedicated on-line registry. S-100 provides the data framework for the development of the next generation of ENC products, as well as other related digital products required by the hydrographic, maritime and geographic information system (GIS) communities.

Work has been completed at the IHO on the latest version of the presentation library which is now mandatory for all systems. IHO is also working on the new ENC standard S-101, derived using S-100. The International Association of Lighthouse Authorities is using S-100 as the basis for the e-Navigation concepts being developed.

Because the new presentation library will mean that new systems will need to incorporate it and older systems may need upgrading, buyers of ECDIS systems should satisfy themselves that they are purchasing a system that conforms to the latest requirements.

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