Compass surveying involves measuring directions with a compass and distances with a chain or tape. It is used when the area is large, undulating, or has many details. There are two types of compasses used - the prismatic compass and surveyor's compass. The prismatic compass measures bearings in degrees from 0-360 while the surveyor's compass measures in quadrants from 0-90. Traversing involves connecting lines and measuring bearings and distances to determine positions without triangulation. Bearings can be true, magnetic, grid, or arbitrary and are expressed using the whole circle bearing or quadrantal bearing systems. Examples are provided to demonstrate converting between systems and calculating interior angles of traverses.
7. • In traversing , the frame work consist of connected lines.
• The length are measured by a chain or a tape and the
direction measured by angle measuring instruments.
• Hence in compass surveying direction of survey lines
are determined with a compass and the length of the
lines are measured with a tape or a chain. This process is
known as compass traversing.
Traversing
8. TypesofBearing:-
The bearing of a line is the horizontal angle which it makes
with a reference line(meridian).
there are four type of bearings :-
1) True Bearing: The true bearing of a line is the horizontal
angle between the true meridian and the survey line.The
true bearing is measured from the true north in the
clockwise direction.
2)Magnetic Bearing: the magnetic bearing of a line is the
horizontal angle which the line makes with the magnetic north.
3)Grid Bearing: The grid bearing of a line is the horizontal
angle which the line makes with the grid meridian.
4)Arbitrary Bearing: The arbitrary baring of a line is the
horizontal angle which the line makes with the arbitrary
meridian.
10. The bearing are designated in the following two system:-
1) Whole Circle Bearing System.(W.C.B)
2) Quadrantal Bearing System.(Q.B)
Measurement of Bearings:
11. Whole Circle Bearing System.(W.C.B)
•The bearing of a line measured with respect to magnetic meridian
in clockwise direction is called magnetic bearing and its value
varies between 0ᴼto 360ᴼ.
•The quadrant start from north an progress in a clockwise direction
as the first quadrant is 0ᴼto 90ᴼin clockwise direction , 2nd 90ᴼto
180ᴼ, 3rd 180ᴼto 270ᴼ,and up to 360ᴼis 4th one.
Quadrantal bearing system(Q.B.)
•In this system, the bearing of survey lines are
measured wrt to north line or south line which ever
is the nearest to the given survey line and either in
clockwise direction or in anti clockwise direction
23. Station Line FB Line BB DiffofFB&
BB
Exterio
r
Angle
Interior
Angle
A AB 45°00’ DA 109°00’ 64°00’ 64°00’
B BC 123°3’ AB 225°00’ 101°00’ 101°30’
C CD 181°0’ BC 303°30’ 122°30’ 122°30’
D DA 289°0’ CD 1°00’ 288° 288° 72°00’
I
nterior angle A =BB of DA – FB of AB
Interior angle B =BB of AB – FB of BC
Interior angle C =BB of BC – FB of CD
ExteriorangleD=FBofDA– BBofCD
SotheInteriorangleD=360°– InteriorangleD
Sumofangles=64°+101°30’+122°30’+72°
=360°
Check=(2N– 4)* 90°
=(2*4– 4)*90°
=360°
25. Station Line FB Lin
e
BB Diff.ofFB
&BB
Exterior
Angle
Interior
Angle
A AB 20°30’ DA 106°0’ 85°30’ 85°30’
B BC 110°00’ AB 200°00’ 90°00’ 90°00’
C CD 195°00’ BC 290°30’ 95°30’ 95°30’
D DA 286°30’ CD 15°00’ 271°30’ 271°30’ 88°30’
Sum=359°30’
Interior angle A =BB of DA – FB of AB
Interior angle B =BB of AB – FB of BC
Interior angle C =BB of BC – FB of CD
ExteriorangleD=FBofDA– BBofCD
SotheInteriorangleD=360°– InteriorangleD
Sumofangles=85°30’+90°00’+95°30’+88°30’=359°30’
Check=(2N– 4)* 90°
=(2*4– 4)*90°
=360°
∴TotalError=359°30’– 360°=–30°