Theodolite and its working mechanism
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The document summarizes the key components and operation of a theodolite surveying instrument. It describes the history of the theodolite's development from its early invention in the 18th century to modern digital versions. The main parts of a theodolite including its horizontal and vertical circles are explained. The document also outlines how theodolite measurements are taken and discusses potential sources of error.
Theodolite and its working mechanism
- 1. 1 Theodolite And Its Working Mechanism Binabh Devkota binabhdevkota@gmail.com Course: Control Surveying (GEOM 202) Teacher: Er. Shangharsha Thapa
- 2. 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 2
- 3. 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 3
- 4. Parts of Theodolite(Vernier) 4 S N Parts S N 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 Illuminating Mirror 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
- 5. Additional Parts (Digital Theodolite) 5 1. On Board Battery 2. Keypad 3. LCD Screen -measured value displayed on screen(no need of reading eyepiece) -may have storage capacity
- 6. 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 6
- 7. 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 7
- 8. 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 8
- 9. 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 9
- 10. 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 10
- 11. 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. 11
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