Understanding a Nautical Chart by Paul Boissier

Author:Paul Boissier [Boissier, Paul]
Language: eng
Format: epub
Tags: TRANSPORTATION / Navigation
Publisher: Fernhurst Books Limited
Published: 2018-01-08T21:00:00+00:00

Wrecks

Multi-beam sonar image of the wreck of a Norwegian freighter sunk in the Dover Strait

On any chart in general use, a wreck will be annotated with the cartographer’s most accurate information of the least depth of water over it. Some, depending on the depth of water, will be classified as ‘dangerous to surface navigation’. The criterion of ‘dangerous’ has increased over the years (see Chapter 3), but any chart drawn after 1968 categorises any wreck with less than 28 metres of clearance as ‘dangerous to surface navigation’ – and it will be drawn on the chart with a dotted ‘necklace’ around it.

Any semi-competent mariner needs to be able recognise the different wreck symbols that are shown on his chart, and explained in Section K of Chart 5011 (page 156 of this book). These aren’t particularly difficult to learn – more significant is the message that they are giving you over the level of risk. In general, information on a wreck which has been surveyed by modern surveying techniques (since about 1973) is likely to be accurate, as will the information on a chart that has been swept by wire. A wreck that has only been surveyed by echo sounder in a survey pre-dating the advent of sidescan sonar may, however, be less accurate.

It goes without saying that the depth of the wreck, if less than 5 or 10 metres (depending on the convention of that particular chart) will be shaded blue as an additional caution to the mariner.

If you look at this chart of the north-east coast of Brittany, you will see a number of relatively ugly obstructions scattered across the approaches to Saint-Quay-Portrieux.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.