ECDIS – Contour Settings

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Traditional method of passage planning on paper chart:

ecdis contour setting

Using a draft of 14 mtr and applying a 2 mtr safety margin, the second mate would mark off areas with depth 16 mtrs and less, on the navigational chart.

ecdis contour settings

These areas would then be highlighted, using a pencil, as a NO GO area and the passage would be planned keeping well clear of this area.

ECDIS Contour Settings

Correspondingly on ECDIS

ECDIS Contour Settings

When the safety contour value is set as 7 mtrs.

ECDIS Contour Settings

⦁ Safety contour is emphasized (bolder) than other contours.
⦁ If the safety contour specified by the mariner is not in the displayed SENC, the safety contour shown defaults to the next deeper contour.

ECDIS Contour Settings

⦁ ECDIS will give an alarm if, within a specified time set by the mariner, own ship crosses the safety contour.

ECDIS Contour Settings

⦁ Areas with depths lesser than the set safety contour is coloured blue and deeper depth area is coloured white.

ECDIS Contour Settings

⦁ Enabling the “shallow pattern” provides a cross hatch pattern to further emphasis the NO GO area as was done on paper charts.

ECDIS Contour Settings

Hence like the traditional NoGo areas on a paper charts, on an ECDIS,
Blue area denotes NO GO areas
White area denotes the navigable area.

If the entire planned passage upto the pilot station is through the “white” and the “Grey” areas [without any planned entry into the blues], followed by a channel/river transit to the berth:

ECDIS Contour Settings

Then at no point in the voyage, the vessel’s planned track is expected to cross into the blue areas.
In this case
⦁ By setting safety contour setting

ECDIS Contour Settings

⦁ And enabling the shallow contour pattern,
The No Go area is automatically marked by the ECDIS. There is, generally, no need to additionally mark NoGo areas using mariner info overlay.

What should the OOW do an obtaining a safety contour alarm?

ECDIS Contour Settings

OOW should call the master immediately and alter course back into grey/white zone if you are about to violate the NO-Go area.

By just feeding in the safety contour setting, the ECDIS ENC display is sub-divided into blue (no-go) and white (navigable) zones.

ECDIS Contour Settings

Changing over from 2 color mode to 4 color mode and by entering appropriate values for shallow contour setting and deep contour setting, we find that:

ECDIS Contour Settings`

⦁ The blue area gets subdivided into dark blue and light blue areas.

ECDIS Contour Settings

⦁ The white area gets subdivided into grey and white.

What does the colour indicates

DARK BLUE ZONE:

ECDIS Contour Settings

On inputting the shallow contour setting, areas on the ENC with depth value <= Shallow contour setting is displayed as dark blue zone.

Example:-

Assuming vessel static draft of 7.80 mtr
With shallow contour setting at 5.00 mtrs

ECDIS Contour Settings

Dark blue zone denotes grounding depths.

ECDIS Contour Settings

LIGHT BLUE ZONE:

ECDIS Contour Settings

On inputting the safety contour setting, areas of the ENC with depth value lesser<= Safety contour setting is displayed as light blue zone.

Example:-

Safety contour setting = (Static draft + all allowances + Minimum net UKC requirement for that area – Height of tide)

ECDIS Contour Settings

Vessel is in congested waters , Height of tide as 1.5 mtrs, we take 0.50 mtrs as the minimum net UKC requirement.

Giving us

Safety contour setting = 7.8+3.0+0.5-1.3 = 10.0 meters
With safety contour setting at 10.0 mtrs

Light blue zone denotes an area where you are in non-compliance with the Minimum Net UKC policy of the company.

ECDIS Contour Settings

GREY ZONE

ECDIS Contour Settings

On inputting the deep contour setting, areas of the ENC with depth value <= Deep contour setting is displayed as Grey zone.

Grey zone denotes an area of potential shallow water effects

White zone is relatively safe waters

No Go Area :- Dark Blue Zone and Light Blue Zone

IMO “standard” display setting is the minimum ECDIS layers considered essential by IMO for safe navigation.

The “standard” display des not include the sounding layer as the four colours shown on the ECDIS display provide sufficient data for anti-grounding purposes.

Example:-

The pilot station is situated within the light blue zone (No go area) of the ENC.
We will use a vessel with draft of 12 mtrs.

ECDIS Contour Settings

Dynamic Draft= 12+1.9 (all allowances ie. Squat, heel correction, density correction and others) = 13.9 m
Safety Contour Settings = 13.9+0.5-0.4 = 14.0 m
Safety depth = 14.0 m
Shallow contour = 10.0 m

ECDIS Contour Settings

Vessel has to pass the safety contour area to enter channel

ECDIS Contour Settings

When the vessel first crosses the safety contour, the safety contour alarm will be generated to alert the navigator to a potential violation of the NO GO area.

ECDIS Contour Settings

However no further Anti-grounding warnings will be generated, if for any reason, the vessel deviates off her planned route.

ECDIS Contour Settings

Why ECDIS has this issue

The ECDIS ENCs like the earlier paper charts, have sounding contour layers of 5/10/15 or 05/10/20 / 30 or 100/200/300 etc.

ECDIS Contour Settings
ECDIS Contour Settings

Hence, when we set the safety contour setting as 14 mtrs, the ECDIS defaults to the next available contour which is 20 mtrs.

ECDIS Contour Settings

So though the light blue area is a No-GO area as per the ECDIS display, technically we can navigate in waters with depths> the safety contour setting of 14 mtrs (highlighted as NAVIGABLE )

Depths <=14 mtrs (highlighted as NO GO and cross hatched with red lines ) are still No-Go depths as the vessel will likely be violating the UKC policy of the company.

The risk associated with navigation in these safer areas within the light blue zones are:

ECDIS Contour Settings

⦁ Availaible sea room inside light blue area is generally confined or restricted for safe navigation
⦁ Soundings are not easily visible, more so in the night mode
⦁ No more alarms are generated once the vessel crosses the safety contour

Configuring the ECDIS for crossing the safety contour

As per above the safety depth setting is set at 14m , so all depths <=14 m will appear bold.

ECDIS Contour Settings

Spot soundings with depth <= safety depth will appear bold.

Note

These are not required to generate any alarms as per the IMO performance standards

Lets make some modification on ECDIS for more safe passage planning

Using user maps (mariner info overlays), demark the no-go areas within the light blue zone. (only usermap lines with danger attribute will generate alarms when interrogated by the safety cone)

ECDIS Contour Settings

Use warning lines to follow the virtual 14 mtrs (safety depth setting) contour indicated by the darker safety depths.

ECDIS Contour Settings

Note:

These warning lines will generate an alarm when interrogated by the vessel’s look ahead (danger detection) cone

ECDIS Contour Settings

Navigate within the light blue zone with the vessel look ahead (danger detection) cone activate.

(Ensure that look ahead cone time or distance setting is carefully set to meet the particular circumstances.

Note:

If set too long it will create numerous alerts that may distract the navigator.

Obstructions (dangerous to navigation)

ECDIS Obstructions

All obstructions (dangerous to navigation) with an attribute equal to or lesser than the safety contour setting will be highlighted with a Magenta Cross Head Symbol.

ECDIS Obstructions

Any obstructions (dangerous to navigation) with an attribute more than the safety contour setting will not be highlighted with a Magenta cross head symbol.

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