Furuno FMD-3100 Manual page 23

ii. Workaround #2
Two colour pattern is used.
Safety contour is set to the previous shallower depth contour than the safe draft. For example if the safe depth
is 13 metres and the available depth contours are 10m and 20m then the safety contour is set at 10m.
Safety depth is set equal to safe draft and No-Go Areas are drawn manually by the navigator.
Advantages
• Image clear even in dusk and night time setting.
• Applicable isolated dangers will be shown up to the safety contour depth setting.
• Vessel will sail through 'safe' waters. This might be considered as a disadvantage as more water will be
portrayed as safe than what is actually safe but the advantage will be that the navigators are getting
accustomed to how the display should look.
• Safety contour alarm will not sound without it being actually applicable.
Disadvantages
• Procedure for setting depth alarm settings (safety depth, safety contour) is more complicated than the
procedure in Workaround #1
• Area portrayed as safe (area outside the safety contour) does not correspond to the reality.
• Safety contour alarm will not sound at the proper depth but will sound at a later stage.
Fig 11: Safety contour=10m, Safety depth=13m, two color depth selected and No-Go Areas
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are drawn manually by the navigator
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