What is collimation error in theodolite?
If the line of collimation of the telescope is not truly perpendicular to the trunnion axis, it generates a cone when it is rotated about the horizontal axis. This introduces errors in horizontal angles measured between stations at diļ¬erent elevations.
What is meant by collimation error?
Collimation error is due to the line of sight of a survey instrument not coinciding with traversing gear, scales, or leveling devices. The collimation line is the line of sight, passing through the intersection of the crosshairs of the reticule.
What is line of collimation in theodolite?
Line of collimation : Line joining the intersection of the cross-hairs to the optical center of the objective and its continuation. It is also know as Line of sight. Line of sight : is defined as the intersection of the cross hairs and the optical centre of the objective lens. It is tangent to a Horizontal line .
What type of error is collimation error?
The error of Collimation or simply the collimation error is a common type of error in reciprocal levelling. This type of error occurs when the axis of collimation is not truly horizontal when the instrument is level. The axis of collimation is tilted concerning the horizontal by a certain angle.
How do you fix a collimation error?
The collimation error is compensated by multiplying the correction by the BS and FS length difference and adding it to the elevation difference. This requires the length of each sight be captured as the readings are taken.
How do I fix collimation error?
In differential leveling, the effect of a level’s collimation error can be almost entirely eliminated by carefully balancing the foresight length with the backsight length. However, in some settlement monitoring studies, the sheer number of points (or their close spacing) makes such balancing impractical.
How do you use collimation error?
What is the difference between line of sight and line of collimation?
The key difference between the line of collimation and the line of sight is that the former is characterized as ‘the intersection point of cross-hairs and the optical center associated with the objective as well as its continuity’ while the latter is described as the ‘intersection point of center and cross-hairs of the …
How can error levels be reduced?
How to eliminate error due to Curvature and Refraction
- Proper field procedures (taking shorter shots and balancing shots) can practically reduce errors.
- Wherever possible, staff readings should be kept at least 0.5 m above the ground,
- Using short observation distances (25 m) equalized for backsight and foresight.
How do you calculate collimation error?
Aim at rod A and press MEAS (4/4). The measurement displays; press ENTER to accept/confirm. The new “collimation error” is displayed in seconds of angle and corresponding dH vertical error in mm at that distance. To accept the correction, press the ENTER key.
Why is collimation error important?
Collimation error is much more significant than the other errors. It should be kept as small as possible so that one need not be too precise in ensuring that fore and back sights are of equal length. It is possible to determine the collimation error and reduce its size using Two-peg test.