What is 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.

How is collimation Height calculated?

To find the Height of Collimation (Instrument Height) add the staff reading to the level of the Bench Mark. The survey station is below the horizontal plane through the instrument, so to find reduced level, or ground height, take the staff reading away from Height of Collimation.

How do you calculate horizontal collimation error?

To test for horizontal collimation error, point to a target in face one then point back to the same target in face two; the difference in horizontal circle readings should be 180 degrees. Horizontal collimation error can always be corrected for by meaning the face one and face two pointings of the instrument.

What is Rise and Fall method?

Introduction. The rise and fall method is the method of calculating the difference in elevation between consecutive points in levelling work. Some of the points you have to know before starting numerical are: Back sights: The first reading after seeing the instrument is called back sights.

How do you fix a 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.

What is HI method?

Height of Instrument Method. In any particular set up of an instrument height of instrument, which is the elevation of the line of sight, is constant. The elevation of unknown points can be obtained by subtracting the staff readings at the desired points from the height of instrument.

What is the difference between height of collimation and rise and fall?

Answer: The difference between Height of Collimation Method (HCM) and Rise and Fall Method (RFM) are as follows: HCM :It is more rapid and saves a considerable time and labour. RFM : It is laborious as the staff reading of each station is compared to get a rise or fall.

How do you find the collimation error in reciprocal leveling?

Error in observation = 0.924 – 0.801= 0.123 m. Error due to curvature and refraction is 0.069 mts. Therefore error in collimation is 0.123 + 0.069 = 0.192 m. If ∆ is the inclination of line of the site then tan∆ = 0.192/1010 = 0.000190.

How do you adjust collimation errors?

What is horizontal collimation error?

Horizontal collimation or line of sight error is when the line of sight is not perpendicular to the tilting axis of the instrument. This is an axial error. Line of sight error effects the horizontal angle readings and increases with steep sightings. The error can be overcome or eliminated by observing on two faces.