Electronic Chart Systems.
Charts may be classified as.
Harbor plans and Physical charts.
However, to get the most form your charts you need to understand the abbreviations and symbols which are used.
Marine charts have been honed over the centuries to contain all the information needed by the navigator at sea.
There is such a wealth of information that it would be impossible show it without resorting to a form or shorthand.
And as sea travel is such an international occupation this short hand has become fairly well standardized world wide.
Many of the charts published, especially for the leisure boater have a guide to the symbols and abbreviations printed on the reverse side and there are various publications with quick guides.
However, most of the symbols and abbreviations are fairly self explanatory once you begin to understand the shorthand and develop an understanding of boat navigation.
Of course it will depend
on the scale of the
chart as to how much information it can show.
The first thing to remember is that the top of the marine chart is always true north, rather than magnetic north.
But it will also include compass roses depicting the variation between magnetic and true north at that location and at the time of publication.
The next thing to be aware of is that although some charts may display a distance scale, distances should be taken from the latitude scale on the side of the chart.
Distances at sea are measured in nautical miles, one nautical mile is one minute of latitude.
Because of the projection, any distance must be measured from the scale adjacent to the area being measured.
To get the best pilotage information from your chart you need to have an understanding of how your particular chart displays the information.
Depths for instance are shown on most charts in meters.
However, some old charts and those published by the United States Government may use feet or fathoms.
And how they are displayed will depend on the chart datum used.
This will be indicated on the chart.
The most commonly used datums are ‘lowest astronomical tide’ and ‘mean lower low water’.
Most marine charts will also show such things as the nature of the seabed, navigational hazards, symbols for lights, lighthouses, buoys and land structures and features, and a host of other aids to navigation.
Tidal information, such as tidal races and other strong currents are also displayed using symbols.
tidal flow information
can be found by reference to tidal diamonds and their accompanying
Buy Portland course plotter and dividers kit at the RYA Shop
As comprehensive as the
information on marine
charts is, the prudent navigator can supplement this knowledge with
books, sailing directions, tide tables, lists of lights and
Any marine chart can only be correct at the time of its publication.
There are areas where the profile of the seabed changes due to erosion shifting sand banks etc and artificial navigation aids may be moved or altered for various reasons.
It is therefore unwise to use old, uncorrected charts for navigation.
Any changes to the position of lights and buoys will be issued as "Notices to Mariners".
These corrections should be added to your charts as soon as practicable.
All publishers of marine charts provide a system to inform you of any changes.
Government and coast guard agencies also issue notifications of chart corrections by way of Notice to Mariners, Local Notice to Mariners, Summary of Corrections, and Broadcast Notice to Mariners, and radio broadcasts of any urgent corrections.
Corrections to paper charts should be done as neatly as possible and in waterproof ink.
Electronic navigational marine charts have a variety of methods for inserting corrections.