Sources of errors in theodolite surveying:-
i) Instrumental errors1) Non adjustment of plate bubble.
2) Line of collimation not being perpendicular to horizontal axis.
3) Line of collimation not being parallel to axis of telescope.
4) Horizontal axis not being perpendicular to vertical axis.
5) Eccentricity of inner and outer axes
6) Graduations not being uniform.
7) Verniers being eccentric.
ii) Personal errors1) Imperfect centering and leveling.
2) Improper fixing of clamps.
3) Improper use of tangent screws.
4) No parallax removing.
5) No accurate bisecting.
6) Verniers may not set in proper place.
7) Over sighting in reading vernier.
iii) Natural errors1) High temperature causes error due to irregular refraction.
2) High winds cause vibration in instrument.