Basics of Chartwork

Universitatea Maritima din Constanta Terrestrial Navigation

Assist. Prof. Costel STANCA

BASIS OF CHARTWORK


2

PLOTTING THE DEPARTURE

Plotting using the nautical triangle

Example: Z1 (φ1 = 48°15’.4N ; λ1 = 033°19’.2E)

Latitude

• First, we should have a look on the chart in order to estabilish the area

of the nautical chart where the departure is falling into: left/right,

up/down.

• Lay off the first nautical triangle with the line from the middle of the

triangle such us to overlay the closest meridian to the left latitude scale;

• Using the second triangle hypotenuse fix one of the first nautical triangle

legs. Keeping the second triangle fixed on the nautical chart you should

now advance the first, until its hypotenuse reaches the latitude φ1 =

48°15’.4N;

• Mark this latitude with a short line using the pencil, in the area where it

should meet the longitude λ1 = 033°19’.2E.


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PLOTTING THE DEPARTURE (cont.)

Longitude

• Lay off the first triangle with the line from the middle of the triangle

such us to overlay the closest parallel line to the below longitude scale;

• Using the second triangle hypotenuse fix one of the first nautical triangle

legs. Keeping the second triangle fixed on the nautical chart you should

now advance the first, until its hypotenuse reaches the longitude λ1 =

033°19’.2E;

• Mark this longitude with a short line using the pencil, in the area where

it should meet the latitude φ1= 48°15’.4N.


4

Plotting the latitude

48

15’

20’

33 20’ 25’ 30’


5

Plotting the longitude

48

15’

20’

33 20’ 25’ 30’


6

Plotting using the parallel ruler

Latitude

• First, we should have a look on the chart in order to establish the area of

the nautical chart where the point is falling into, and also to identify the

closest meridian and the closest parallel to our point;

• Lay off the parallel ruler horizontally with one of the rulers aligned

with the closest parallel to the ship’s position; Ex: φ = 46°40’N;

• Keeping this aligned line fix you should advance the second line so that

to reach the latitude φ2 = 46°38’.2N;

• Mark this latitude with a short line using the pencil, in the area where it

should meet the longitude λ2 = 042°52’E


7

Plotting using the parallel ruler

Longitude

• Lay off the parallel ruler vertically, with one of the rulers aligned with

the closest meridian to the ship’s position; Ex: 042°50’E;

• Keeping this aligned line fix you should advance the second line so that

to reach the longitude λ2 = 042°52’E;

• Mark this longitude with a short line using the pencil, in the area where

it should meet the latitude φ2 = 46°38’.2N.


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Plot the ship’s position using the compas

Step 1

Example: φ3 = 41°11’.1N ;λ3 = 022°43’2E)

• First, we should have a look on the chart in order to establish the area of

the nautical chart where the point is falling into, and also to identify the

closest meridian and the closest parallel to our point;

• Open the first compass on the latitude scale, with one leg on the closest

parallel to the ship’s position and the second leg to reach the latitude φ3

= 41°11’.1N;

• Open the second compass on the longitude scale, with one leg on the

closest parallel to the ship’s position and the second leg to reach the

longitude λ3 = 022°43’2E;


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10’

13’

45’ 42’2241

4111’.1

2243’.2

1

2


10


Step 2

• Lay off the first compass, opened such was explained in step one, with

one leg on the intersection of the closest parallel with the closest

meridian to the ship’s position, and cross the meridian with the second

leg;

• Then fix one of the second compass legs, opened such was explained in

step one, with one leg on the intersection of the first compass with the

meridian, and draw a short circular arc, representing the longitude λ3 =

022°43’2E;


11


10’

13’

45’ 42’2241

4111’.1

2243’.2

1

2


12


Step 3

• Repet the procedure from the step one, just invers the instruments;

• Lay off the second compass, opened such was explained in step one,

with one leg on the intersection of the closest parallel with the closest

meridian to the ship’s position, and cross the parallel with the second

leg;

• Then fix one of the first compass legs, opened such was explained in

step one, with one leg on the intersection of the first compass with the

meridian, and draw a short circular arc – that intersect the first one

representing the latitude φ3 = 41°11’.1N;

• The intersection of the two small circular arcs represents the ship’s

position Z3.


13


10’

13’

45’ 42’2241

4111’.1

2243’.2

1

2


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READING THE COORDINATES FROM THE NAUTICAL CHARTS

• For reading the plotted ships’ position from the nautical charts you

should follow the above mentioned steps but in inverse sequences.

• The navigational tools that helps us to read the coordinates are: the

nautical triangles, the parallel rulers or the compass/dividers.


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LAYING OUT THE COURSE LINE

Using the nautical triangle

• Ex. The departure point is A (φ = 20°13’.5S; λ = 033°29’.3E). From this point

the vessel proceeds in TC = 060°

Steps:

• Draw the departure point A;

• Put the nautical triangle on the chart such us the center “zero” and the 60

degrees indication to overlay the closest meridian to the ship’s position;

• Fix one of its legs with the other triangle (or a ruler);

• Keep the second triangle (or the ruller) fix. Advance the first triangle

(maintaining all the time its leg on the second triangle hypotenuse, or on the

ruller), until its hypotenuse reaches the ship’s position A

• Draw a line on the first triangle hypotenuse from the point A towards the first

quadrant; the angle between the true north and this line (true course line)

represents the true course of the ship;

• Place an arrow above this course line and indicate its value using three digits,

Ex: 060°.


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A

20 15’S

033 30’E29’

14’

13’060


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Using the parallel ruler

Ex.The departure point is A (φ = 45°02’.3N; λ = 043°16’.3W). From this point the

vessel proceeds in TC = 241°.

Steps:

• Draw the departure point A;

• Put the parallel ruler on the chart such us one of the rulers to be aligned with the

center “zero” and the 241 degrees of the compass rose (the closest compass rose

to the ship’s position);

• Keep one of the two rulers fix. Advance the other ruler (maintaining all the time

one of the rulers in a fix position), until it reaches the ship’s position A

• Draw a line from the point A towards the third quadrant; the angle between the

true north and this line (true course line) represents the true course of the ship;

• Place an arrow above this course line (with the heat into the proceeding

direction) and indicate its value using three digits, Ex: 241°.


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A

241

4315’20’

45

2’


19



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LAYING OUT THE BEARING LINE

Steps: (Ex. TB = 140°)

• First you should identify on the nautical chart the Navigation Aid to which the

Bearing has been sight;

• Put the nautical triangle on the chart such us the center “zero” and the 140°

indication to overlay the closest meridian to the ship’s position;

• Fix one of its legs with the other triangle (or a ruler);

• Keep the second triangle (or the ruler) fix. Advance the first nautical triangle

(maintaining all the time its leg on the second triangle hypotenuse, or on the

ruler), until its hypotenuse reaches the ship’s position A;

• Draw a line on the first triangle hypotenuse from the Navigation Aid (not exact

from the Nav Aid in order not to overlap the mark form the chart) towards the

ship’s position; the angle between the true north and this line (towards the Nav

Aid) represents the true bearing;

• Place the time indicating the moment when the Nav Aid has been sight above

this true bearing line and below it indicate its value using three digits, Ex: 140°.


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LAYING OUT THE BEARING LINE

A

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Basics of Chartwork