Repetition method: Difference between revisions
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In [[surveying[]], the '''repetition method''' is used to improve precision and accuracy of measurements of horizontal angles. The same angle is measured multiple times, with the survey instrument rotated so that systematic errors tend to cancel. The [[arithmetic mean]] of these observations gives true value of an angle. The precision of the measurement can exceed the [[least count]] of the instrument. used.<ref name="NPTEL">{{cite web | url=http://nptel.ac.in/courses/105107122/modules/module6/html/73.htm | title=National Programme of Technology Enhanced Learning | accessdate=6 September 2014}}</ref> |
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| ⚫ | The repetition method is used when high accuracy is required. For rough or approximate survey work, the ordinary method of measuring horizontal angles is less time consuming.<ref>Surveying Volume 1 by Dr. B.C Punmia, Dr. Ashok Kumar Jain and Dr. Arun Kumar Jain. published by Laxmi publications New Delhi. Retrieved on 6 September 2014</ref> |
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==Example== |
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Consider horizontal angle AOB, where '''O''' is the station point.The steps followed to determine horizontal angle AOB by repetition method can be summarized in below mentioned steps: |
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==Procedure== |
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* Firstly the [[theodolite]] is mounted on tripod stand with its proper adjustments. |
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* The theodolite is then centered over the selected station '''O''' and is properly levelled using its foot screws and the plate bubble is brought to the centre of the run. Then using its focusing screws the points '''A''' and '''B''' are properly sighted by telescope. Centering, levelling and focusing of theodolite are called as [[temporary adjustments of theodolite]]. |
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*The theodolite is set on the face left mode and vernier A is set on 0 by making it coincide with 0 of main scale with the help of upper clamp and its tangent screw and station A is sighted by using lower clamp and its tangent screw.<ref name="RM">{{cite web | url=http://www.civilengineeringnews.tk | title=Civil engineering hub | accessdate=6 September 2014}}</ref> Also check whether vernier A still reads 0.<ref>A text book of surveying by Dr. C L Kochher. Retrieved in August 2014</ref> |
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*Now unclamp the upper clamp and rotate the instrument towards B in clockwise manner until it is accurately bisected with the help of upper tangent screw. Note the readings of verniers A and B to get the value of angle AOB. Vernier A gives value of angle AOB directly while Vernier B gives value of angle by deducing its reading by 180. |
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*Tight the upper clamp so that the vernier reading does not change and loose the lower clamp and turn the [[telescope]] clockwise to sight A again. Bisect A accurately by using lower tangent screw. Tight the lower clamp and unclamp the upper clamp, turn the telescope clockwise and sight B. Bisect B accurately using upper tangent screw. |
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*Repeat the process until angle is measured required number of times usually 3.The average angle will be the arthemetic mean of total angle measured. |
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*Same procedure can be used while computing values for face right mode. |
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*The true value of horizontal angle is then computed by taking average of the angles obtained with face left and face right.<ref>{{cite book | title=Surveying | publisher=Laxmi publications New Delhi | author=B.C. Punmai| authorlink=Measuring Horizontal Angles | year=2014}}</ref> |
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==Conclusion== |
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==See also== |
==See also== |
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Revision as of 15:44, 5 December 2014
In [[surveying[]], the repetition method is used to improve precision and accuracy of measurements of horizontal angles. The same angle is measured multiple times, with the survey instrument rotated so that systematic errors tend to cancel. The arithmetic mean of these observations gives true value of an angle. The precision of the measurement can exceed the least count of the instrument. used.[1]
The repetition method is used when high accuracy is required. For rough or approximate survey work, the ordinary method of measuring horizontal angles is less time consuming.[2]
See also
References
- ^ "National Programme of Technology Enhanced Learning". Retrieved 6 September 2014.
- ^ Surveying Volume 1 by Dr. B.C Punmia, Dr. Ashok Kumar Jain and Dr. Arun Kumar Jain. published by Laxmi publications New Delhi. Retrieved on 6 September 2014