5-1
5. VECTOR (S57) CHARTS
Theoretically a chart can be coded for use on a computer as a vector chart. Vector-
coded charts are coded using a variety of techniques. One technique is called S57ed3
and it has been chosen by IMO as the only alternative for SOLAS compliant electronic
charts. If an S57ed3-coded chart is published by a government-authorized Hydro-
graphic Office, then it is called "ENC". You can read more about ENC and related legal
issues in this chapter. 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". 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.
5.1 Introduction to S57 Charts
An ENC chart is encrypted to prevent unauthorized use so the user needs a permit to
view the ENC. This permit could be entered manually from the Control Unit, loaded
from a USB flash memory.
Any new ENC must be loaded into the system. Some parts of the charts may be date
dependent, i.e., they are visible after a set date or they are visible only for a limited
period, etc. For all date-dependent objects set the Display Date and Update Review
dates, referring to section 5.2.2. In the paper chart world, the Preliminary and Tempo-
rary 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:
1. Incremental updates, which are small additions to original base cells.
2. 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
can set a date period and create an update report for that period (see section 5.4).
Chart material is stored in media such as DVD ROM, CD ROMs and USB flash mem-
ory or electronically through from LAN (Local Area Network) in which it could have ar-
rived in DVD ROMs, CD ROMs or USB memories. 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 a medium.
Each S57 chart may contain additional links to textual descriptions or pictures, besides
the chart itself. Typically additional textual descriptions and pictures contain important
sailing directions, tidal tables and other traditional paper chart features that do not
have any other method to be included into the S57 chart. This system copies these
textual descriptions and pictures into its SSD so the user may cursor-pick them for
viewing purposes.
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