8-1
8. Vector Chart Material
8.1 Introduction
Theoretically a chart can be coded for use on a computer as raster or vector chart. Vector-coded charts are coded
using a variety of techniques. One technique is called S57ed3 and it has been selected by IMO as the only
alternative for SOLAS compliant electronic charts. An S57ed3-coded chart published by a government-authorised
Hydrographic Office is called "ENC". An S57ed3-coded chart published by a private firm is called "NON ENC".
Another vector coding technique is known as CM-93/2, and it is employed by the private firm C-MAP. All CM-93/2
charts are NON ENC. For further details about C-MAP charts, see Appendices 4 and 5. You can read more about
ENC and related legal issues in Chapter 7. Hereafter, all references to vector chart material are referred to as "S57
charts" regardless of their source.
Sometimes you may wish to manually add Notices to Mariners or Navtex warnings into your S57 charts. This is
called "manual updates". Manual updates are valid for both S57 and ARCS charts so you need to define them only
once. Also, manual updates are valid for all scales so that you don't need to repeat them for charts published in
different scales from the same area. See Chapter 10 "Manual Updates".
8.2 S57 Charts
8.2.1 Introduction
The electronic chart system is compatible with official IHO S57 release 3 chart material produced by Hydrographic
Offices (HO). This material, when issued by a government-authorised Hydrographic Office, is called ENC
(electronic navigational chart). Use, presentation and display of S57 charts are based on International Maritime
Organisation (IMO), International Hydrographic Organisation (IHO) and International Electrotechnical Commission
(IEC) regulations and rules (S52ed3.1). When this ECS (Electronic Charts System) uses an ENC chart (S57 release
3 chart produced by a government-authorised Hydrographic Office), it is an ECDIS as defined by IMO, IHO and
IEC.
Some ENCs are encrypted to prevent unauthorised use. In this case, the user needs a permit to view the ENC. This
permit could be entered manually from the Control Unit, loaded from a floppy disk, USB memory or loaded through
telecommunications from an RENC.
Before any ENC can be used in the ECDIS, it is loaded into your hard disk and converted into the system’s own
internal format (SENC). Some parts of the charts may be date dependent, i.e., they are visible after a certain date or
they are visible only for a limited period, etc. In the electronic chart system, you control all date-dependent objects
with Display Until and Approve Until dates. In the paper chart world, the Preliminary and Temporary Notices to
Mariners represent the date dependency described above for S57 charts.
An important part of ENCs are the updates. Hydrographic Offices can issue two kinds of updates:
• Incremental updates, which are small additions to original Base cells.
• Reissues and new editions, which are complete replacements of previous Base cells and their updates.
All updates are date stamped and they may also contain date-dependent parts. You control usage of updates in the
electronic chart system from Display Until and Approve Until dates. Using Display Until and Approve Until dates,
you can view your charts correctly drawn on any date in the past or in the future.
Chart material is stored in media such as CD-ROMs and floppies, electronically from LAN (Local Area Network) in
which it could have arrived from RENCs, CD-ROMs or floppies. Such material can contain only basic cells, cells
and updates or only updates. The electronic chart system contains as standard the software required to access CD-
ROMs, floppies and LAN.
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