A navigation chart is one among the most basic and evitable tools available to the seafarers for navigation. It can be considered a map that depicts the entire configuration of the shorelines , seafloors and details of the water ways and areas that are taken into consideration while navigating . It provides minute details such as water depths, naval and submarine exercise areas that are treacherous for vessels along with the areas that are aid for navigation, anchorages and various other features.
The nautical chart is very necessary and essential for safe and sound navigation. Charts are used in the planning of voyages , understanding the area of sea waters to avoid treacherous sea water,and it helps in the safe navigation and it helps to explore more economical routes and voyages.
Difference between Navigation Chart and Map.
A nautical chart usually provides the data including the hydrography of the places and it provides every minute details of water depth, information like tidal predictions and etc. whereas, the term “map,” focuses and highlights landforms and depicts the overall geographic and cartographic details. Some prominent examples of maps are road maps or atlases, etc. A map generally represents topographical details.
Basic Requirements and Procedure
The basic requirements for Chartwork and the procedure for chart work and proper usage of Chart are mentioned below.
These points must be considered while doing chart work.
1.Scale of the Chart
The Scale of the chart is the initial and the foremost thing to check before starting the Chart work. The chart scale is mentioned below the title or name of the Chart. The graduations of latitude and longitude should also be checked along with depth scale.
2. Notes of the Chart
After familiarizing with the chart scales, the notes which are mentioned below the chart name should be read as they provide necessary information regarding the navigation through that area. The information includes naval exercise area, anchoring, traffic separation, tidal information etc.
3. Chart Symbols
A proper knowledge of chart symbol is a must. Without the proper understanding of the correct symbols and it’s meaning, the reliability of the chart work will fade and there will be more chances of errors .
4. Chart Corrections
All the charts are to be kept updated with the permanent and temporary corrections that are received. The permanent ones are marked using magenta ink and temporary corrections are marked using pencils. Plotting of course lines near or above any corrections should be avoided. One should always check the if the corrections are up to date as the temporary corrections may fade out time to time.
5. GPS Positions
GPS positions allow the direct plotting directly on all new BA Charts as they remain in the WGS-84 Datum. GPS positions provide an accuracy of around 50 meters. One should avoid the plotting of GPS positions in coastal areas and restricted waters as such margins are treacherous.
6. Radar Fixes
One of the most reliable fixes in Coastal waters are the radar fixes. Radar fixes functions the best when they are fixed along with Radar conspicuous objects such as Racon or Ramark. These two are marked on the charts by a magenta Circle. One should notice them on charts and use it for position plotting.
7. Visual Fixes
Visual fixes also help in getting reliable positions while one is navigating near land. They are generally taken from the light houses and other navigation aids. Azimuth rings can be utilised to obtain the bearings from the objects and the bearings should be carefully plotted for the fixes.
8. Position Circle and Position Line
Position Circle is a circle drawn from an object with the object at its centre and the vessel distance from the object as its radius . And the line drawn from the object along its bearing from the ship is called position Line , the ship’s position is to be in that line. Using any two parameters A fix can be obtained. A ie, two lines/ two circles/ one line and position circle. Using more parameters provides greater accuracy.
Navigation charts and the chart work is a very essential part of a safe voyage so utmost care should be taken with proper functioning of each and every equipment involved in these activities as the mere change in bearings compromise the vessel’s safety.