Brief overview of bearing systems in land surveying

In this useful civil engineering video tutorial, the renowned engineer S.L. Khan briefly explains the definition of bearing in surveying and it’s system of reading.

The bearing of a point refers to the number of degrees in the angle that is calculated in a clockwise direction from the north line to the line linking the centre of the compass with the point. The bearing of a line stands for horizontal angle that it creates with a reference line (meridian). Based on the meridian, four types of bearings are found :-

True bearing: The true bearing of a line belongs to the horizontal angle among the true meridian and the survey line. The true bearing is calculated from the true north in the clockwise direction.

Magnetic bearing: The magnetic bearing of a line belongs to the horizontal angle that the line creates with the magnetic north.

Grid bearing: The grid bearing of a line refers to the horizontal angle that the line creates with the grid meridian.

Arbitrary bearing: The arbitrary bearing of a line belongs to the horizontal angle that the line creates with the arbitrary meridian.

Designation of bearing - The bearing is designated on the basis of following two systems :-

a. Whole circle bearing system alias W.C.B
b. Quadrantal Bearing System (Q.B.)
c. Whole circle bearing system alias W.C.B

The bearing of a line that is calculated with reference to magnetic meridian in clockwise direction is defined as magnetic bearing and its value fluctuates among 0 degree to 360 degree.

The Quadrants commence from North and proceed in a clockwise direction since the first quadrant remains at 0 degree to 90 degree in clockwise direction, 2nd 90 degree to 180 degree, 3rd 180 degree to 270 degree and up to 360 degree is 4th one.

Quadrantal Bearing System (Q.B.): Under this system, the bearing of survey lines are calculated with reference to north line or south line either is close to the provided survey line and either in clockwise direction or in anticlockwise direction.

The bearing of lines, which belong to 1st and fourth quadrant are calculated with reference to north line is closer as compared to south line and bearing of lines belong to 2nd and third quadrants are calculated from south line as south is the closer line. The surveyor’s compass calculates the bearing of lines in the quadrant system.

Reduced Bearing: If the whole circle bearing of a line is transformed to quadrantal bearing it is called as Reduced Bearing. In this way, the reduced bearing is equivalent to the quadrantal bearing. It’s value remains among 0 degree to 90 degree, but the quadrants should be expressed for perfect designation.

Go through the following video tutorial to get more clear ideas with graphical presentation.

Video Source: SL Khan