Safety parameters should be well understood, clearly defined within the Company SMS and correctly applied, with due consideration for the vessels position, charted depth and surrounding navigable waters/ hazards. Hence, during the voyage, there are likely to be several changes to the safety parameters that must be clearly identified in the passage plan.
The value of the safety contour should be calculated during the planning phase and entered by the OOW. The Safety Contour marks the division between "safe‟ and "unsafe‟ water. When the safety contour is not displayed to the specified value set by the navigator, then the safety contour is shown to the next deepest contour as per the default layers in the electronic charts. During route planning, an indication will be made if the route is planned to cross the ship’s safety contour. At the time of route monitoring, ECDIS should give an alarm if, within a specified time set by the navigator, own ship is likely to cross the safety contour.
The Safety Depth highlights individual soundings in bold that would appear where the sounding is less than the level set on the safety depth alarm. This is generally set the same as the safety contour.
Safety Frame or Safety Cone is equally as important as the Safety Contour, as this will provide an early indication of the vessel running into danger or approaching an area of concern. Equally, if the safety frame is set too large then the ECDIS is likely to provide alarm overload with the result that an essential alarm may possibly be ignored.
