Electronic Chart Correction

 

 

Keeping the ECDIS fully up to date should be a high priority for the bridge team and should be treated as equally important as normal paper chart corrections.

 

The Master must ensure that all charts, ENC’s or Raster, are operating under the latest updates from CD/ROM’s .In case the corrections are being received directly via the communication computer from the provider then these corrections should be received once per week and a Base DVD will be received quarterly. In the event of not receiving the weekly updates from the provider directly via communication computer or through CD/ROM, master must immediately contact the Technical Department and/or the Admiralty Supplier. It is important that the Master check the expiry date of all permits/licenses and to record them, to avoid unplanned and dangerous situations such as losing the chart’s display. Once the latest update CD is received on board, transferring and updating procedure should be carried out immediately as described in Operator’s Manual.

 

On Vessels equipped with full ECDIS (two fully independent ECDIS provided) the requirement for the reception of weekly NTM, including all corrections applicable to chart folios in use, must be met. If, for whatever reason, this requirement is not met, such as corrections are not received timely, or a technical failure to upload the corrections is experienced, the Master must immediately notify the Technical Superintendent and Purchaser.

 

In case regular electronic chart corrections are not provided for the ECDIS, the equipment must not be used for navigation at any time

 

ECDIS software creates a database from the ENC data called the system electronic navigational chart (SENC) and from this selects information for display. The ECDIS software meanwhile receives and processes serial data from navigational sensors and displays that textual and graphical information simultaneously with the SENC information. It is the SENC that is equivalent to up-to-date charts, as stated by the Performance Standards.  As originally conceived, ECDIS was designed to use internationally standardized and officially produced vector data called the ENC (electronic navigational chart). Only when using ENC data can ECDIS create an SENC, and thereby function in the ECDIS mode.

 

Updates for ENC are installed into the ECDIS separate from the ENC data itself. For the mariner, this involves activating a special utility accompanying the ECDIS and following the on-screen prompts. Within this same utility, update content and update log files in textual form can be viewed. Once the ECDIS software itself is reactivated, the update information is accessed in conjunction with the ENC data and the SENC database is created.

 

ECDIS should store and display on demand a record of updates, including the time of application to the ECDIS database, known as the system electronic navigational chart (SENC). This record should include updates for each ENC until it is superseded by a new edition

 

Just as ENC and updates are transformed into the SENC, so too are other data types accessed and combined. The user has the option to add lines, objects, text and links to other files supported by application. Referred to in the Performance Standards as data added by the mariner, these notes function as layers on the displayed chart. The user can select all or parts of the layers for display to keep clutter to a minimum. The mariner’s own layers, however, must be called into the SENC from stored memory. As a practical matter, not only must the mariner take care to associate file names with actual content, such as with manually created chart corrections, but also must realize that the files themselves do not have the tamper-proof status that ENC and official updates have.

 

 

Within the SENC resides all the information available for the display. The Presentation Library rules such as Standard Display and Display Base define what levels of information from the SENC can be shown. An ENC updating profile is contained within the IHO S-57 Edition 3.0 specification. This enables the efficient addition, removal or replacement of any line, feature, object or area contained within the ENC dataset. Guidance on the means and process for ENC updating is provided in IHO S-52, Appendix 1. In terms of what is called for in the IMO Performance Standards, an ENC dataset being used in an ECDIS must also have an ENC updating service. This permits the ENC and the SENC to be corrected for the intended voyage, and thus achieves an important component of SOLAS compliance.

 

Accordingly, ECDIS must be capable of accepting official updates to the ENC data provided in conformity with IHO standard. Updated cells are stored in a file and transmitted by e-mail, floppy disk or CD-ROM, or satellite. For example, PRIMAR charts and updates are delivered on two CD’s: the Base CD contains the PRIMAR database at the time indicated on the label and the second CD contains the updates for those charts. But the update CD also contains new charts issued since the base CD was printed. Since the operator must acquire the files and then initiate the update functions of the ECDIS software, this form of updating is referred to as semi-automatic.

 

 

Generally, ECDIS will reject updates if the update issuing authority is different from the cell issuing authority. It will also reject corrupted update files and files with an incorrect extension. ECDIS checks that updates are applied in the right sequence. If one update is missing the next update is rejected. An update CD-ROM should contain all available updates for all S57 cells. Generally, ECDIS will automatically run all updates in the right order for all cells. For S-57 data, the content of updates in text form can be viewed from within the utility that permits the management of chart data. Generally it can only be run when ECDIS is terminated. ECDIS is also capable of showing or hiding S-57 updates on a given chart or cell. The update must first be installed via the chart utility. After restarting ECDIS, and after loading into the display the particular chart with the correction, the correction should be manually accepted. That enables the function in S-57 chart options to show or hide the symbol indicating the location of the correction.

 

 

British RCS Corrections

 

 

For the British RCS system, updates for all 2700 charts affected by Admiralty Notice to Mariners are compiled and placed on a weekly ARCS Update CD-ROM. Applying the corrections is only semi- automatic (not fully automatic), but it is also error-free, and each CD-ROM provides cumulative updates. The CD-ROM’s are available through chart agents.

 

 

NOAA Corrections

 

 

In the U.S., NOAA has contracted with Maptech, Inc. to provide updating of all NOS raster charts using information from the USCG, NIMA and the Canadian Hydrographic Service (CHS). Maptech uses a “patch technique” to update only those parts of a given chart identified as needing correction. The method compares the existing chart file and its corrected counterpart on a pixel-by-pixel basis. The software creates a “difference file” that is associated with the existing raster file to which it applies. This difference file is then compressed so that a typical patch contains only a few kilobytes of data. Ninety- nine percent are under 10kb. Typical downloads for a chart take 15 seconds to 5 minutes depending on modem speed.

The raster chart is updated as the patch file alters the pixels on the original chart. Update patches are available by download, and are cumulative for the all the charts packed on a given source folio CD. Further refinement will permit the separate storage of the RNC and update patches, so that as the patch is applied dynamically in real time, the user will be able to view the correction. The dynamic patching is similar to ENC updating in that the original chart data is not altered.

 

 

PMS

Recommendations. The Quarterly, Monthly and Weekly checks should include the below, however it is not restricted to the below items only and other type specific equipment requirements must be included in the PMS.

 

 

The Staff onboard must test ECDIS on backup power, check user chart function, ECDIS electronics log book, cell permit, tracker ball and keyboard, system safeguards such as Password protection are active and tested at least on monthly basis.

 

 

Ensure Antivirus is up-to-date and check must be done on all USBs and CDs used in the system. Weekly checks of chart (ENC, RNC and paper if carried) correction and other updates, connectivity of all equipment’s (channel view) and ship's position verification between GPS and ECDIS must be performed.

 

 

All alarms and indicators as per IMO A.830 (19).2 must be tested on weekly basis. UPS battery conditions must be checked on monthly basis.

 

 

The IHO ENC / ECDIS data presentation and performance tests are to be done on a quarterly basis whenever the latest base-DVD data was copied to the ECDIS, after an ECDIS failure, after technical services conducted and after the system was upgraded. The results are to be recorded in the PMS and the test report is to be submitted to the vessel’s superintendent. The superintendent must submit the test result to the IHO via their web interface at www.iho.int.

 

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