Their is still a lot of confusion between the Safety Contour and the Safety Depth found from the inspections.

Safety Contour

The Safety Contour  distinguishes between safe and unsafe water and to generate alarms against your planned and monitored route. By default on an ECDIS system the Safety Contour is set at 30 m. The Safety Contour is highlighted on the screen with a bold line.

Three contours can be set for vector charts only together with a means of accentuating spot depths.
If the values you enter do not correspond to a contour available in the chart, the next contour up will be used.

e.g. If the chart on display has 5m and 10m contours and you have set your safety contour at 6m, then the 10m contour will be used as the safety cont

The Safety Contour parameter cannot be larger than the Safety Depth parameter. If the operator sets a larger value, the same value is automatically assigned
to the Safety Depth parameter, and vice versa, if the operator sets a smaller value for the Safety Depth parameter, the same value is automatically assigned
to the Safety Contour parameter.

If, with a change of chart under the ship position the previously selected safety contour becomes unavailable, the Safety Contour alarm is generated. In this case, the safety contour is automatically set as equal to a deeper available depth contour.

Safety Depth
This is a value set by the operator that serves to detect depths that are a danger to navigation. By default, the Safety Depth is set to 30m. A depth equal to or less
than the Safety Depth is highlighted on the ECDIS task screen in bold type when the display of spot soundings is turned on. If such danger is detected, the Nav Danger alarm is triggered.

It could be set, for example, to the ship’s draught plus under keel clearance.

e.g. If you told the system that your safety depth was 2m it wouldn’t alarm on a 5m shoal.

It is recommended that Safety Depth be likened to an LDL and set as follows:

LDL = Squat + Draught + Safety – HoT

Don’t forget height of tide as you may have to subtract Height if tide if you don’t have integrated total tide.