(v) The error due to dishevelment of the bubble can be minimised by taking precautions in levelling. If not, the discrepancy is equally distributed among all the measured angles. [gravityform id="1" title="false" description="false" ajax="true"]. (v) Loosen the upper clamp and turn the telescope clockwise until the line of sight is set nearly on the right hand object (B).

Account Disable 12. Report a Violation 11. (b) Error due to the unequal graduations. The mean of the two vernier readings gives the second value of the angle ABC which should be approximately or exactly equal to the previous value. This method is used for very accurate work. Bisect it accurately by using the lower clamp and its tangent screw.

(Suppose the mean reading is 50°4′). This website uses cookies to improve your experience while you navigate through the website. The final reading of the vernier A should be the same as its initial reading. 2. Content Filtration 6. (xi) Again measure the angles in the same manner by turning the telescope this time in the counter-clockwise direction to compensate or slip and errors due to twisting of the instrument. Huge Collection of Essays, Research Papers and Articles on Business Management shared by visitors and users like you. are introduced. (vii) The vernier A should now read 360°. (iv) Loosen the upper clamp, turn the telescope clock-wise and bisect the right hand object (B) exactly by using the upper clamp and its tangent screw. This site uses cookies.

Such procedure (closing the horizon) can be applied even when only one angle is measured. Ordinary Method. If you do not agree to the use of cookies, you should not navigate (viii) The mean of the two values of the angle AOB, one with the face left and the other with the face right, gives the required angle free from all instrumental errors. this website. Content Guidelines 2.

(iii) Direct the telescope to some well-defined object (P) or say, the station point A, which is known as the ‘Reference object’. All Rights Reserved BNP Media. In this method; the same angle is added several times mechanically and the correct value of the angle is obtained by dividing the accumulated reading by the number of repetitions. The mean of the two vernier readings (after deducting 180° from the reading at vernier B) will give the value of the angle AOB. Disclaimer 8. By visiting this website, certain cookies have already been set, which you may delete and block. This is done to detect the error caused by turning the wrong tangent screw. The method provides an easy way for a beginner to test instrument readings and pointings. Three repetitions with face left and three repetitions with face right are quite sufficient except in cases of very precise work.

These cookies will be stored in your browser only with your consent. Bring the point A into exact coincidence with the point of intersection of the cross-hairs at diagram by using the vertical circle clamp and tangent screws. (The face of the instrument should be left.). (vii) Loosen the upper clamp, turn the telescope clock-wise and again sight towards B. Bisect B accurately by using the upper tangent screw. Alternatively bring the vertical cross-hair exactly on the lowest visible portion of the arrow or the ranging rod representing the point A in order to minimise the error due to non- verticality of the object. The reading of the vernier A which was initially set at zero gives the value of the angle AOB directly and that of the other venier B by deducting 180°. Bisect A accurately using the lower tangent screw. Copyright 10.

The observations are recorded in the tabular form as given in Table 9.1. This website requires certain cookies to work and uses other cookies to

9.6.) and cookie policy to learn more about the cookies we use and how we use your Visit our updated, This website requires certain cookies to work and uses other cookies to help you have the best experience. But opting out of some of these cookies may affect your browsing experience. The verniers will now read twice the value of the angle (It should he approximately 100 °8′). Closing the Horizon - A technique in traversing control for horizontal measurements. Read both verniers. Then tighten the upper clamp and by turning its tangent screw, bisect B exactly. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. Lovingly crafted and maintained by. Repeat exactly in the same manner and find another value of the angle AOB. This method consists in measuring the several angles successively, and finally closing the horizon at the starting point. Design, CMS, Hosting & Web Development :: ePublishing, This website requires certain cookies to work and uses other cookies to help you have the best experience.

(v) Read both verniers- The object of reading the verniers is to obtain the approximate value of the angle. In this operation, the lower clamp and its tangent screws should not be touched. The vernier A is initially set to zero for convenience only. this website, certain cookies have already been set, which you may delete and Turn the instrument and direct the telescope approximately to the left hand object (A) by sighting over the top of the telescope. To measure the horizontal angle AOB by repetition: (i) Set up the theodolite at station -point O and level it accurately.

Problems in Ranging and Chaining of a Line | Chain Surveying | Surveying, Unconventional Machining Processes: AJM, EBM, LBM & PAM | Manufacturing, Material Properties: Alloying, Heat Treatment, Mechanical Working and Recrystallization, Design of Gating System | Casting | Manufacturing Science, Forming Process: Forming Operations of Materials | Manufacturing Science, Generative Manufacturing Process and its Types | Manufacturing Science. (v) Similarly bisect C and D successively, read both verniers at each bisection, find the values of the angles BOC and COD. (viii) Repeat the process until the angle is repeated the required number of times (usually 3). (xii) Close the horizon and apply the necessary correction to all the angles as before. It may be set at any other reading, and the difference between the initial and the final readings of the vernier A will give the value of the angle AOB. Check the reading at vernier A which should still be 0 or 360° and note the reading at vernier B. In this way, angles can be measured to a finer degree of accuracy than that obtainable with the least count of the vernier. Closing the horizon is good for spur points, to show that a mistake wasn't made.

If large, the readings should be discarded and a new set of readings be taken.

(iv) Loosen the upper clamp and turn the telescope clockwise until the point B is exactly sighted by using the upper tangent screw. (vii) Change the face of the instrument and repeat the whole process.

Repetition Method. Tighten the upper clamp and turn its tangent screw to bring the two zeros into exact coincidence. It is generally preferred when several angles are to be measured at a particular station. Reiteration is another precise and comparatively less tedious method of measuring the horizontal angles. Read the vernier B and record both vernier readings. Then to measure these angles by reiteration method: (i) Set up the instrument over station point O and level it accurately. Divide the sum by the number of repetitions and the result thus obtained gives the correct value of the angle AOB. Plagiarism Prevention 5. (vi) Loosen the lower clamp and turn the telescope clock-wise until the object (A) is sighted again. If not, note down the error. Prohibited Content 3.

(vi) Finally, close the horizon by sighting towards the reference object (P) or the station-point A. The mean of the two vernier readings (after deducting 180° from the reading on vernier B gives the value of the required angle AOB.). data. Check the vernier readings which must be the same as before. : To measure horizontal angle AOB: (i) Set up the theodolite at station … Suppose it is required to measure the angles AOB, BOC and COD.

Ordinary Method (Fig.

This is done to avoid errors of graduation. (c) Error due to the line of collimation not coinciding with the axis of the telescope. (iv) Having sighted the object A, see whether the vernier A still reads zero. By closing this message or continuing to use our site, you agree to the use of cookies. (ii) Set the vernier A to 0 or 360° by using the upper clamp and its tangent screw. (x) The average of the two values of the angle thus obtained gives the required precise value of the angle (AOB). Read both verniers.

Terms of Service 7. Doubling angles on a traverse takes insignificantly more time than just turning single angles, and it's definitely worth doing. Tighten the lower clamp and bisect A exactly by turning the lower tangent screw. Image Guidelines 4. (ii) Set the vernier A to the zero or 360° of the horizontal circle so do this, loosen the upper clamp and tum the upper plate until the zero of vernier A nearly coincides with the zero of the horizontal circle. Privacy Policy 9. Before uploading and sharing your knowledge on this site, please read the following pages: 1.