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Acre = 10 square chains 10 chains = 660' 66' 660' x 66' = 43,560 sqft (acre) Figure 2: Surveyor’s Chain Other multiples of the chain are still in use today. in which Ct = the correction for temperature, in m. a = the coefficient of thermal expansion. It is the most Important line, fixes up the directions of all other lines. 3. The chain survey is the simplest method of surveying. 2. Correction per tape length = α ( (Tm – To)L, Sag correction per tape length = 0, Pull correction per tape length = (Pm - Po)L / AE. If l is the length of any one slope, and h the difference in height between the ends of the slope, = l – l (1 – h2 / 2l2 – h4 / 3l4 – etc..), =(h2 / 2l + h4 / 3l3 + etc.) Tm = the mean temperature during measurement. 3. It is given by the formula. 4. The R.L, of the point A which is on the floor is 100 m and back sight reading on A is 2.455 m. ~ The required correction = 0.82 / 2 x 30 = 0.0167 m. Hence the horizontal length = 30 – 0.0167. This measurement hence requires correction. Refraction correction a) completely eliminates curvature correction b) partially eliminates curvature correction c) adds to the curvature correction d) has no effect on curvature correction Ans: b. The temperature of the field is greater than the temperature at which the tape is standardised; Tm > To. The measurement of this linear horizontal distance between two points on the earth surface is known as linear measurement. iX0��X_g٪��*�5�������骺��10.#����:Z�biqxX����"� ��ܜ�'���WuqB���a�x"�Eu����*'�
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��#˽. After participating in this fieldwork students will become more comfortable with handling chain and ranging rods. in which l = the length of the slope : 0 = the angle of the slope. REFERENCES – Surveying Notes Pdf 1. This document is highly rated by Agricultural Engineering students and has been viewed 3538 times. This results in an increase in the tape length, making the measured length shorter. It is given by the formula. This is suitable for the survey of small areas with simple details and an area that is fairly flat. effects which act in a predictable manner and therefore can be corrected by mathematical methods. 58. If there are n equal spans per tape length, the sag corrections per tape length is given, by, Cs = nl1(mgl1)2 / 24P2 = l(mgl1)2 / 24P2 = l(mgl)2 / 24n2P2 ………….(4a). Ideal Conditions 1) A tape accurate to 0.00305m or 0.01 ft should be used. Since the accuracy of the whole survey work depends upon the accuracy of the base line, it should be laid off on the ground level as much as possible. This is suitable for the survey of small areas with simple details and an area that is fairly flat. m = the mass of the tape, in kilograms per metre. Where Cp = the correction for pull in metres. �"N5�e�@"���� What is the horizontal length? <>
Procedure for surveying the given open field (Closed Traverse): Note: This procedure is general procedure only. When a tape is stretched over points of support, it takes the form of a catenary. To = the temperature at which the tape is standardized. Take coefficient of expansion of the tape per oC=0.0000117. The correction for the measured length is given by the formula. LAB #3: SURVEY OF AN AREA BY CHAIN SURVEY (CLOSED TRAVERSE) Objective: To survey an open field by chain survey in order to calculate the area of the open field. MODULE-I-B. Surveying and leveling by R. Subramanian, Oxford university press, New Delhi. Chain surveying is the branch of surveying in which only linear measurements are made in the field. By the former is meant it’s designated length, e.g. Rods are commonly used in early highway right-of way descriptions. The tape may be standardized when supported horizontally throughout its full length or in catenary. in which Cs = the sag correction for a single span, in metres. In actual practice, however, the catenary curve is assumed to be a parabola. The following corrections are to be made for measurements taken with a tape because tape can never be practically used under specified standard conditions. Measuring distances for a variety of survey purposes, such as the length of a baseline between two survey stations. Normal Tension: - The normal tension is a tension at which the effects of pull and sag are neutralized, i.e. It is required only when the tape is suspended during measurement. no angular measurements are made. Before use it is desirable to ascertain its actual length (absolute length) by comparing it with the standard of known length, which can be done for a small fee by the Survey and Standards department. In this method the lengths of lines marked on the field are measured, while the details are measured by offsets and ties from these lines. Chain survey is the simplest method of surveying. 4) Measurement of bearings of sides of traverse with prismatic compass and computation of correct included angle. Linear measurement In engineering survey, the linear horizontal distance is to be measured to complete a survey. Arthur R Benton and Philip J Taety, Elements of Plane Surveying, McGraw Hill – 2000. If these conditions are not met we can have a huge variation in result. 2 • Surveying has to do with the determination of the relative spatial location of points on or near the surface of the earth. Eliminate or correct all systematic errors by frequent calibration and adjustment of the instruments Minimize the random errors by using good instrumentsandfieldprocedures. = the lengths of successive uniform slopes. Find the corrected length of the tape. in which Pn = the normal tension in newtons (N). It may be obtained by equating the corrections for pull and sag. Not correcting for these effects gives rise to systematic errors, i.e. The combined correction can be application two ways: (i) By decreasing each staff reading by the amount 0.0673 D 2 and then finding, the reduced levels and (ii) By first finding the reduced levels of the points in the usual way and then increasing them by the amount 0.0673 D 2. Tape Corrections: - Precise measurements of distance is made by means of a steel tape 30 m or 50 m in length. Surveying is a very important part of Civil Engineering.It is a basic course for all universities for civil engineers. stream
The longest chain line in chain surveying is often called the base line. The measurement type can be divided as, direct measurement method, optical … For surveying, we need to have some prerequisite conditions. Tape Correction, Sag Correction, Pull Correction and Temperature Correction. The expression that “a tape is standard at a certain temperature and under a certain pull” means that under these conditions the actual length of the tape is exactly equal to its nominal length. Surveying is often called the base line the correction is always subtractive from measured. A chain and Ranging rods met we can have a huge variation result... And eliminatealltheblunders of expansion for the survey of small areas with very few details, we need have. Or designated length, e.g than the temperature is above standard, then the tape =,! Out a chain measuring horizontal distances by Agricultural Engineering students and has been viewed 3538 times the nominal designated! 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