What does the term height of collimation refer to?
Height of Collimation is the elevation of the optical axis of the telescope at the time of the setup. The line of collimation is the imaginary line at the elevation. Orders of levelling refer to the quality of the levelling, usually being defined by the expected. maximum closing error.
What is the height of collimation method?
Height of Collimation is the height of the horizontal plane through the telescope. 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.
What does Hi mean in surveying?
Height of instrument
Height of instrument (HI) – the elevation of the line of. sight of the telescope. Starting point.
What is mean by collimation method?
The collimation method is the height-of-instrument method of leveling whereby fore-and-aft readings are made on a leveling staff by an instrument placed intermediately so that the rise or fall between the fore station and the back station is shown by a change in the staff reading. See Also: rise and fall. ii.
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.
What does collimation mean in surveying?
The line of sight of the telescope of a surveying instrument, defined as the line through the rear nodal point of the objective lens of the telescope and the center of the reticle when they are in perfect alignment.
What is TBM elevation?
Temporary Bench Mark (TBM) = A point of known elevation. Turning Point (TP) = An intervening point between BMs or TBMs upon which a backsight and a foresight are taken.
What is height of instrument in Levelling?
Height of instrument: It is the elevation or reduced level of the line of sight with respect to the datum. The height of the instrument is not the height of the line of sight above the ground where the leveling instrument is set up. In stadia leveling, the height of the center of transit above the station stake.
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 HI and rise and fall method?
Line of Collimation or HI method Rise and fall method Rise and fall method. 1. It is more rapid and saves a considerable time and labour. It is laborious as the staff reading of each station is compared, to get a rise or fall. 2.
What is instrument height?
What is the difference between BM and TBM?
Bench Mark (BM) = A permanent point of known elevation. Temporary Bench Mark (TBM) = A point of known elevation.