The image presents different water depth limitations when navigating with an ENC in ECDIS. Mariners can set an advance time warning to indicate when the vessel is approaching the set limits. The following limits can be set:
Safety depth:The depth defined by the mariner, e.g. the ship's draft plus underkeel clearance, to be used by the ECDIS to emphasize soundings on the display equal to or less than this value.
Safety contour:The contour related to the own ship selected by the mariner from the contours provided for in the SENC, to be used by ECDIS to distinguish on the display between the safe and the unsafe water, and for generating anti-grounding alarm.
If an ENC does not offer a depth for the selected water depth, the next deeper option will be selected instead.