ECDIS
0 (0 Likes / 0 Dislikes)
For centuries, seafarers have relied
on paper charts for safe navigation.
With advances in technology,
and knowledge of the sea,
the Electronic Chart Display and Information
System, or ECDIS, is the new navigational standard.
ECDIS is an alternative to paper charts that complies with International Maritime Organization regulations.
In this program, we will learn the basics of ECDIS,
including chart systems, regulatory requirements,
watchkeeping and alarms, dangers
of ECDIS, and passage planning.
There are two types of electronic charts, Raster Navigation Charts, also called RNCs, and Electronic Navigation Charts, called ENCs.
RNCs are images of existing paper charts and contain only visual and positioning information.
ENCs, also called vector charts, contain much
more data than Raster or paper charts.
ENCs can be scaled, rotated, and queried as needed with the ability to enable or disable layers of information to declutter or augment the display.
ECDIS is a valuable resource for
crew working on the bridge.
One screen may combine the display inputs from the GPS, gyrocompass, ARPA, and even more.
ECDIS integrates data from navigational equipment with the electronic
chart to form the SENC, or System Electronic Navigation Chart.
This data is then displayed
at the ECDIS terminal.
All of this information can help improve situational awareness on the bridge and make passage planning more effective and efficient.
This is why the fitting of ECDIS aboard
most ships now is mandatory.
In 2009, the International Maritime Organization
amended SOLAS chapter five regulation 19
to require most ships engaged on international voyages
to be fitted with ECDIS, according the following timetable.
SOLAS also requires that ECDIS is backed up, either with
a folio of paper charts, or with a redundant ECDIS system.
To meet SOLAS requirements and ensure accurate charting information, the ECDIS system must be updated weekly.
Depending on the distributor, chart up dates
will be installed via DVD or download.
Both the primary and backup
ECDIS must be updated.
To meet IMO requirements, every officer of the watch
assigned to a ship using mandatory ECDIS,
or any vessel using ECDIS for primary navigation,
must undergo IMO Model Course 1.27 training.
The type training may be provided by
a trained ship's officer and documented.
A tremendous advantage of ECDIS over paper or Raster charts is the
variety of settings and alarms to help keep watchkeepers better informed.
Another benefit is that all navigational information can be
overlaid on the display for comparison and verification.
As with paper charts, it is vital that the navigator chose
the correct chart scale for the task at hand.
Navigating coastal waters with ECDIS
set to scale for oceanic transit
can be extremely dangerous as some
navigational hazards may not be visible.
The watch vector is perhaps the
most important ECDIS setting.
The watch vector is also known as the
anti-grounding cone, or look ahead setting
and is based upon the stopping distance
and turning radius of the vessel.
The watch vector defines the area in which ECDIS will
alarm, should the vessel approach a navigational hazard.
Without this setting, the ECDIS
will provide no advance warning.
Additionally, watchkeepers should verify the safety
contour and spot depth settings on the ECDIS.
The broadest depth setting is the safety contour depth which
provides a visible boundary between safe and unsafe water.
The safety contour depth is set by the
navigator to reflect the vessel's safety draft,
which is commonly calculated at the vessel draft
plus dynamic squat, plus the safety margin.
ECDIS displays soundings
as well as depth contours.
Safe soundings are indicated by the safety depth. In most situations,
the safety depth and safety contour depth will be the same.
Safety depths should never be
less than the safety contour.
Navigators may choose to display
depth contours in two or four colors.
It's most important that navigators verify their understanding of the
chart display as settings like night mode may lead to confusion.
Additional depth information can be displayed
by the shallow and deep contours settings.
Most importantly, Raster charts can not be read by the ECDIS.
Vector data is necessary for navigational alarms.
If functioning in Raster Chart Display System,
or RCDS mode, the terminal will not warn of navigational
hazards. ECDIS can be very useful for passage planning.
Some of the features include graphical way-points, track data for
the autopilot, voyage schedule calculation, and safety checks.
Passage planning on the ECDIS system begins with either selecting a pre-created
route or creating a new graphical passage plan by plotting the way-points.
If part of the passage is not covered by ENC charts,
mariners may use the ECDIS terminal in RCDS mode.
In this configuration, the ship must have up-to-date paper charts
as backup, and most alarms will not function in this mode.
Once the route is established, the navigator uses the automatic
check function of ECDIS to asses the track and identify any hazards.
It is imperative that the safety contour, watch vector,
and cross track deviation are set correctly.
After the navigator has adjusted the track and addressed any alarms, it's
then approved by the master and loaded for use throughout the voyage.
ECDIS is only as safe a tool
as the navigators who use it.
Overreliance on ECDIS can lead to
dangerous lapses in situational awareness.
Careful planning, cross checking, and a vigilant watch
are still the keys to the safety of the ship and all aboard.
Just one of the many accidents blamed on
the misuse of ECDIS, the grounding
of the chemical tanker Ovit in the Dover
Strait was a close call to disaster.
Investigations revealed that the master had delegated passage
planning to the third officer, who had little prior experience.
The third officer planned the track on
ECDIS and checked the track visually.
The third officer did not realize that
this planned course ran directly
across The Varne Bank, a dangerously shallow
hazard and part of a traffic separation scheme.
When the master checked the course, he disregarded the
numerous alarms generated by the automatic route check.
While navigating the Dover Strait, the
master set the map scale to 1:350.000
when a scale of 1:45.000 would have been
appropriate for channel navigation.
Visual ECDIS depth contour, cross track deviation, and map scale alarms
were all ignored and the audible ECDIS alarm was never configured.
ECDIS aside, buoys marking the east and west sides of The Varne
Bank were visible at five nautical miles, but not reported by the watch.
The master was unaware that the ship was aground until a call
from the Coast Guard prompted him to look closer at the ECDIS.
Any ECDIS alarm should be fully
investigated by the officer of the watch.
In the case of the Ovit, a simple look out the bridge
window could have prevented the grounding.
Fortunately, the crew avoided injury and the
vessel sustained minimal damage.
ECDIS is required to save track and instrument data in a log for at
least the previous 12 hours and may save these records indefinitely.
Location data is recorded in four hour or shorter
increments across the entire voyage.
The crew should know how to preserve ECDIS
data in case of a marine accident and investigation.
Ultimately, ECDIS is a powerful
addition to bridge operations.
The success or failure of ECDIS depends on
you, the mariner, to be informed and vigilant.
In this introduction to ECDIS, we learned about
the critical importance of chart scaling,
IMO requirements for the use of ECDIS,
learning how to set safety contours,
depth, and watch alarms, understanding the
dangers of ECDIS, including overreliance
and position errors, and passage planning,
including route safety checks.
Mastery of ECDIS allows the observer improved awareness,
preventing navigational errors and maritime causalities.
With this elegant solution at hand, you can
always stand your watch with confidence.