Safety Contour doesn't help!? Insufficient depth soundings data in ECDIS on approaches to Chesapeake Bay

Nowadays mariners are well aware of the importance of anti-grounding function in ECDIS. It is well clear that any alarm emerged while route checking should be addressed seriously, especially if such alarm is relevant to the anti-grounding assessment. Here we wish to discuss one of such alarm occasions, which you may experience approaching the Chesapeake Bay in North America while heading to such ports as Baltimore or Norfolk.

Approximately in 30 nm from Chesapeake Bay Entrance Whistle Buoy (Lat. 36-56.1N; Long. 075-57.4W) true bearing 120° (ENC US3DE01M), there are some areas with isolated soundings of 146 m and deeper surrounded with 182 m contour. But if your route is laid through those areas you may notice an anti-grounding alarm on the ECDIS. You will see that those areas are marked as Shallow Water even if your Shallow and Safety Contours are set well below 182 m. Why does it happen? 

It happens because information on the chart is insufficient. Within the contour depth values may be anywhere from 0 to 182m, which means that something there may be reaching up to the water level!

Basically, because there is only one distinctive contour on the chart, any Safety Contour setting below 182 m (even 1 m) will highlight this contour (182) and fill the area within it with blue color. In our case Safety Countour = Safety Depth = 10 m. Also, note that ENC compilation scale is 1:350 000 and ZOC category is "C" (part of the display to the right on the picture below).

Read more about ZOC categories in this article. 


Why did we come to the conclusion that information on this chart is insufficient? 

Because, if you have a look on the ENC US4NC32M (left part of the display) with compilation scale 1:80 000 and ZOC A1 Safety Contour is not highlighted at all.

This means that in this area there is no depth less than 10 m (at least on the larger scale chart) as it shown on the screenshot below.


Also, the raster chart for this area gives the same information:

The appropriate hydrographic office will be informed via contracted Chart Supplier about those findings. Meanwhile, it is recommended to perform Passage Planning in this area with particular attention, carefully checking chart information with relevant ECDIS tool.   

Learn more about ECDIS Safety Settings with our ECDIS Awareness course. 
4542 views

Our courses

Seafarers' Rights

Ship's Cook Refresher Course

High Voltage Equipment

Time Management

Comments

Related articles

INMARSAT is not the only GMDSS satellite service! New amendments to SOLAS Chapter IV on GMDSS

INMARSAT is not the only GMDSS satellite service! New amendments to SOLAS Chapter IV on GMDSS

The International Maritime Organization (IMO) has revised the SOLAS Chapter IV requirements for the Global Maritime Distress and Safety System (GMDSS) to reflect advancements in technology and to...

17 January 2024
1552 views
E-mail etiquette in maritime industry: best practices

E-mail etiquette in maritime industry: best practices

Email is one of the most common and important forms of communication in the modern world, especially for businesses that operate across borders and oceans. However, email etiquette can vary depending...

24 July 2023
1514 views
STCW Maritime Security Training - which one do you need?

STCW Maritime Security Training - which one do you need?

Maritime security is a vital aspect of the shipping industry, as it protects the lives and property of seafarers, passengers, cargo, and port facilities from various threats and risks. To ensure...

24 May 2023
1545 views