Transas has recently drawn the attention of ECDIS users to a warning published by UKHO in its Notices to Mariners, concerning an issue with the use of electronic navigation charts.

The warning reads: “Mariners are advised of a potentially serious issue that has come to light relating to the way ECDIS displays and operates with some shoal soundings.

 A very small proportion of shoal soundings, especially those marked as ‘reported’ on paper charts, will not be visible when operating in the base or standard display modes and may not trigger automatic grounding alarms in any display mode, even if their depth is less than the vessel safety depth set in the ECDIS. This is due to a specific manner of encoding these particular shoal soundings within S-57.”

UKHO is issuing corrections to ensure that its own ENCs will operate safely, and says that other ENC producing nations are urgently re-examining ENCs and taking corrective action as necessary.

Transas recommends ECDIS users to switch displays to ‘custom’ mode, with the ‘spot soundings’ layer switched on. The company stresses that its own Navi-Sailor ECDIS software generates automatic anti-grounding alarms in voyage planning (check route) and monitoring modes for (S)ENCs, in spite of the fact that such soundings are not shown in ECDIS standard and base display.

Furthermore, the warning should not affect Transas TX-97 charts produced from paper sources since such shoals are always depicted as obstructions and are always displayed. However, the problem could affect TX-97 charts converted from official ENCs.