Types of charts and Mercator Chart projection

Mercator Chart. This is a type of navigational chart. Navigational charts are different from maps in that they are used for navigating ships safely from one place to another. These charts depict the earth's surface which is part of an oblate spheroid tin a flattened two dimensional manner. Various types of projections are used to create various types of chart. One such chart is the mercator chart. These charts are widely used by sea farers in navigating ships.

1. Chart Work

2. CHARTWORK

3. An observed position,otherwise known as a fix, is a reliable position obtained from a minimum of two observed position lines which intersect at a reasonable angle (minimum 30 ) Such position lines could be :- Positions

4. Visual bearings Celestial observation Co-ordinates from navigational aids systems Soundings/depth contours Position circles (ranges) from:- Radar range Dipping range ( will explain later but has to do with lights) Horizontal angles Or any combination of the above Positions

5. A DR (dead reckoning) position is obtained using course and distance run The distance can either be from the log or calculated from engine revolutions Please refer to your handout for a definition Positions

6. An estimated position, EP is the best possible approximation of a present or future position It is based on course and distance since the last known position with an estimation made for set and drift (i.e. tidal/current effect) Please refer to your handout for a definition Positions

7. A small circle should only be used to indicate an observed position, otherwise known as a fix Marking Of Positions A small cross is used to indicate a dead reckoning, DR position A small triangle is used to indicate an estimated position, EP. Except for a fix, always mark positions with the appropriate abbreviation i.e. DR / EP, For all positions insert the time and the log reading, if given

8. Position of Lighthouse This is indicated by the white dot in the centre of the light star

9. Position of Floating Lights The position of a light vessel, light-float, buoy, or beacon is the centre of the base indicated by a small circle :-

10. Position of a Mountain or Peak The position is indicated by a small dot beside the height of the mountain or peak thus:- 495

11. Bearings Unless stated otherwise, any visual bearing or azimuth is named as the direction from the observer towards the object or body being observed Always written in three figure notation

12. Bearings may be given:- relative to True North :- 027 T relative to Compass North :- 319 C relative to Magnetic North :- 243 M relative to Gyro North :- 137 G Bearings may also be given relative to the ship’s head from 0 to 359 Relative (R) In which case relative bearings are always added to the Ship’s Head to obtain True bearing relative bearings are always measured Clockwise from the Ship’s Head Bearings

13. On charts, position lines should be indicated as follows:- Azimuth (bearing of a celestial body) Position Lines OR Transferred Position Lines Marking of Position Lines

14. Bearings of The Needles Light & Poole Harbour Light

15. Bearings of The Needles Light & Poole Harbour Light

16. Radar Ranges of Anvil Point Light and Hengistbury Head

17. The marking of Tracks on a chart A Track is the path followed by a ship between one position and another This track may be the track over the ground, known as the Ground Track , OR The track through the water, known as the Water Track

18. The marking of Tracks on a chart On charts, tracks should be indicated as follows:- Water Track Ground Track Tidal Set So, as an example:-

19. Assuming YOU are leaving Poole Harbour