The following are some of the errors that are associated with a total station survey work. Vertical collimation error, Centering error, Horizontal collimation error, Eccentricity error. Categorize the given errors as those due to temporary adjustments (T) and permanent adjustments (P).
Introduction Horizontal angles can be measured by a compass. But to get precise readings and to measure horizontal and vertical angles another instrument called theodolite is used. It can be used for laying off horizontal angles, locating points on line, prolong- ing survey lines, establishing grades, determining differences in elevation, setting out curves, etc.
There are two types of adjustment necessary, these being the station or temporary adjustments and the permanent adjustments.
Temporary Adjustments of Theodolite
Setting: The instrument to be set over the station, centering by a plumb bob and approximate levelling with the help of tripod legs.
Levelling: Done using leveling screws or foot screws to make the vertical axis truly vertical.
Elimination of parallax: Parallax is a condition arising when the image formed by the objective is not in the plane of the cross hairs. It is done in two steps:
Permanent Adjustments of Theodolite
Adjustment of plate level: To make the axis of the plate bubble perpendicular to the vertical axis when the bubble is central.
Adjustment of line of sight: Line of sight should coincide with the optical axis of the telescope.
Adjustment of horizontal axis: Horizontal axis should be perpendicular to the vertical axis. The spire test is done.
Adjustment of altitude level and vertical index frame: Clip and tangent screws are used for adjusting vertical frame and leveling of altitude.
Error in Theodolite
Temporary Error:- Centering, leveling, and making images and reticles together are the temporary adjustment in the total station.
Permanent Error:- Permanent adjustment of total station consists of.