Errors in Compass Surveying|Civil Easy Learning

Errors in Compass Surveying

Errors in compass surveying are classified as follows:
a) Natural Errors b) Instrumental Errors

a) Natural Errors: Natural errors are of two types:

1. Errors of manipulation and sighting
2. Errors due to external influences

1. Errors of manipulation and sighting

i) Inaccurate centering of the compass
ii) Inaccurate leveling of the compass box
iii) Imperfect bisection of the ranging rods at stations
iv) Carelessness in reading the graduations
v) Carelessness in recording the observed readings

2. Errors due to external influences

i) Magnetic changes in atmosphere on a cloudy or stormy day
ii) Variations in declinations
iii) Local attraction due to proximity of steel structures

b) Instrumental Errors:

i) The needle not being perfectly straight
ii) The pivot being bent
iii) The needle being sluggish
iv)The needle not moving freely.
v) The line of sight is not being vertical.
vi) The graduated circle not being horizontal.
vii) The line of sight not passing through the centre of the graduated ring
and
viii) The vertical hair being loose.