theodolite and its working mechanism
TRANSCRIPT
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Theodolite And Its Working Mechanism
Binabh Devkota
Course: Control Surveying (GEOM 202)Teacher: Er. Shangharsha Thapa
Introduction
• Theodolite
-Optical instrument
-Angle measurement (horizontal and vertical)
-One of the most used instruments
• Theodolite Survey
-Survey using theodolite
-Traversing, triangulation, trilateration
-Contouring and detail mapping
-Setting out on ground
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History Of Theodolite
• First made in 1831 by Philadelphian William J. Young
• Adaptation of the theodolite invented in 1720 by John Sisson of England
-telescope (invented circa 1608)
-Vernier
-device for subdividing measurements by 10ths (1631)
-spirit level (1704)
• Improved versions of Young's transit were still in use for land surveying in the 1950s
• Are still broadly used
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Parts of Theodolite(Vernier)
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SN
Parts SN
Parts
1 Vertical Circle 10 Horizontal Clamp
2 Gun Sight 11 Foot Screw
3 Eye piece (telescope)
12 Objective
4 Eye piece (Reading)
13 Micrometer Screw
5 IlluminatingMirror
14 Vertical Clamp
6 Plate bubble 15 Vertical slow motion
7 Reading Slow Motion
16 Optical plummet
8 Reading Clamp 17 Horizontal circle
9 Horizontal Slow Motion
18 Circular bubble
Additional Parts (Digital Theodolite)
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1. On Board Battery2. Keypad3. LCD Screen
-measured value displayed on screen(no need of reading eyepiece)-may have storage capacity
Terms Used In Theodolite Survey
• Vertical axis: axis about which instrument can be rotated in horizontal plane
• Horizontal(trunnion) axis: axis about which instrument can be rotated in vertical plane
• Line of sight or line of collimation: line through intersection of cross hairs, optical center of object glass and continued
• Swinging: rotating 180⁰ in horizontal plane about vertical axis
• Transiting: rotating 180⁰ in vertical plane about horizontal axis
• Face left observation: observation done when vertical circle is left to observer
• Face right observation: observation done when vertical circle is right to observer
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Adjustments Of Theodolite• Temporary adjustments
-Centering: process in which the vertical axis of the instrument is coincided with the plumb line
-Levelling: making the vertical axis of instrument truly vertical
-Focusing: adjustment of telescope to obtain clear visibility of image through eyepiece and objective lens
• Permanent adjustments
-Horizontal axis adjustment: it must be perpendicular to the vertical axis
-Vertical circle index adjustment: it must read zero when the line of collimation is horizontal
-Adjustment of altitude level axis: it must be parallel to the line of collimation
-Collimation adjustment: line of collimation/line of sight should coincide with axis of the telescope
-Adjustment of horizontal plate level axis: it must be perpendicular to the vertical axis
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Reading The Angles
• Reading horizontal angle
-the horizontal angle reading is set zero
-the signal(ranging rod) is bisected
(opening horizontal clamp)
-horizontal clamp closed, reading clamp open
and bisected to another signal
-angle noted looking at reading eyepiece, exactly adjusted using micrometer screw
• Reading vertical/zenithal angle
-Vertical/zenithal angle can be read simply by intersecting
the point and adjusting the micrometer screw
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Sources of errors in Theodolite Survey
• Instrument Errors
-Non-adjustment of plate bubble
-Line of collimation not being perpendicular to horizontal axis .
-Horizontal axis not being perpendicular to vertical axis.
-Eccentricity of Inner and Outer axes
-Graduation not being Uniform.
• Personal Errors
• Natural Errors
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Inside the theodolite
• Horizontal circle(In horizontal plane)
-graduated from 0⁰ to 360⁰
-can be adjusted
-viewed by reflection to reading eyepiece
• Vertical circle(In vertical plane)
-graduated from 0⁰ to 360⁰
-can’t be adjusted
-viewed by reflection to reading eyepiece
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References
• Geodetic Survey, L. (n.d.). Retrieved January 19, 2017, from History of Surveying - Chicago Area Land Surveying: http://gslandsurveying.com/history-of-surveying
• surveyhistory.org. (n.d.). The Surveyor's Basic Tools. Retrieved January 20, 2017, from Survey History: http://www.surveyhistory.org/the_surveyor's_basic_tools.htm
• Punimia, D. B., Jain, K. A., & Jain, K. A. (2005). SURVEYING VOL. I. Jodhpur: Laxmi Publications (P) LTD.
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