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Instruments used for compass surveying - GTU e

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Instruments used for compass surveying - GTU e
Compass Surveying (1st Rank)
Prepared ByPatoliya Kaushik (131090119060)
• Shah Abhiskek (131090119068)
• Kaneriya Mohit (131090119034)
• Limbasiya Chirag (131090119041)
• Nadoda Kishan (131090119050)
•
Guided ByMr. Shirish G Bhalodia
Instruments used for compass
surveying:
The various instruments used in the compass
survey are :
 Prismatic compass
 Tape
 Ranging rods
 Tripod
 Arrows
Compass surveying:





The principle of compass surveying is traversing
In traversing .the framework consists of a number of
connected lines
The method of traversing is adopted when the area is
large
The ground is undulating and crowded with many
details
A compass is a small instrument essentially
consisting of magnetic needle . Graduated circle and a
line of sight
Types of compass


The prismatic compass
The surveyor’s compass
Prismatic compass 
Prismatic Compass
•
•
•
Prismatic Compass comprises of a magnetic
needle attached to the circular ring made up of
aluminium.
The needle is on the pivot and will orient itself in
the magnetic meridian Therefore the north and
south ends of the ring will be in this direction.
The line of sight is defined by the objective vane
and the eye slit, both attached to the compass
box.
There are two systems commonly used to
express the bearing.
WHOLE CIRCLE BEARING:
In this system the bearing of a line measured
with the magnetic north in clockwise direction.
The value of bearing thus varies from 0o to
360o.
QUADRANTAL SYSTEM:
In this system the bearing of a line is measured
E or W from N or S whichever is near. The
directions can be either clock wise or anti
clockwise depending upon the position of the
line.
Fore Bearing & Back Bearing:
Every line has two bearings one observed at
each end of the line.
 The bearing of the line in the direction of
progress of the survey is called Fore Bearing
(FB), while the bearing in the opposite
direction is called Back Bearing (BB).
 Therefore BB of a line differs from FB by
exactly 180o.

Errors in Compass observations:
The errors may be classified as
•
Instrumental errors
•
Personal errors
•
Errors due to natural causes
Care should be taken
All magnetic objects, such as belts, watches,
keys, and other metal objects can interfere
with the compass reading.
 Hold compass away from metal objects while
taking a reading.

BALAJI ENGHINEERING COLLAGE
JUNAGADH
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