Depth Contours In Enc In Relation To Safety Contour And Safety Depth Function - Furuno FMD-3100 Manual

Depth Contours in ENCs in Relation to Safety
Contour and Safety Depth Function
1) Introduction
In the era of paper charts the colours defining different depth areas were permanently set. The mariner's only
option to clearly distinguish between areas where he could safely navigate and areas he could not (No Go
Areas) was to manually draw the outline of the No Go Areas and clearly mark them. By doing that the OOW
had a clear picture which waters were safe to navigate through when monitoring the passage of the vessel.
The arrival of ECDIS has changed that. ENCs give the Navigator the option to change the colours of the various
depth areas. He can effect this change by simply inputting in metres the safety contour (safety contour=depth
boundary between 'safe' and 'unsafe' waters).
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Fig 4: Safety Depth 14 metres, Safety contour 10 metres, Isolated dangers with a depth equal to or below
10m shown
The safety contour as explained above intends to provide a visible boundary between 'safe' and 'unsafe'
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water with respect to depth, and is highlighted on the display to enable easy identification, however, to date
and because of the limitation of available depth contours, the safety contour usually cannot perform this
function. This is described at length in para 2) of this chapter.
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