Engi 3703 surveying and geomatics topic instructor. It is the exercise of physically measuring horizontal distances. Correction for standardization, correction for slope, correction of pull, correction for temperature, correction for sag, normal tension, correction for misalignment and reduction of length to mean sea level. Incorrect length sources of error bad repair poor standardization cl ltruel determining add correction establishing subtract the correction incorrect length determining your task. This chain method is performed by a use of tape and it is expected to have errors due to incorrect tape measurements. In surveying, tape correction s refers to correcting measurements for the effect of slope angle, expansion or contraction due to temperature, and the tape s sag, which varies with the applied tension. Without taking a survey of the plot where the construction is to be carried out, the work cannot begin 2.
A correction is said to be plus or positive when the uncorrected length is to be increased, and minus or negative when it is to be decreased in order to obtain true. They are used in taping to permit the surveyor to hold the tape horizontal when the. Earth surface is considered a plane of xy dimensions. Find the centre of the line ab and mark it with point q. Survey field procedures manual prepared by the division of. Basic surveying manual michigan technological university. Chapter 2 tape correction examples slope measurement. Correction for temperature let t0 temperature at which tape is standardised. We will now move on with different numerical problems on the concept of errors in chain surveying. Tape corrections l surveying l civil engineering l gate. A 50m tape weighs 2kg and is supported at its end points and at the 8m and 25m marks. Chapter 2 tape correction examples slope measurement scribd. Above this temperature, the tape elongates and provides distances that are shorter then actual. With the free end of the tape zero reading at point p, form an arc with the tape.
For example temperature correction for a steel tape. Five ways to solve proportion problems understanding ratios and using. If the temperature is above standard, then the tape is too long, and a measured distance will be too short. 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. The primary object of surveying is to prepare a plan or map to show the relative position of the objects on the surface of the earth.
In an ordinary chaining survey, the errors are neglected. This is one of the important subjects of civil engineering. The quality of the end results, however, can only be appreciated by an understanding of the errors involved. A 30m tape is used with a 100n force instead of the standard tension of 50n. But for crucial and precise survey works in construction, accurate tape corrections are provided. A 30m tape is supported only at its ends and under a steady pull of 8 kg. This is the volume obtained by the prismoidal formula. The prismoidal correction is l w1 60 w2 100 c1 10 c2 20 3 60. Precise measurements of distance is made by means of a steel tape 30 m or 50. Pdf surveying problem solving saied albayya academia. However, in highly sophisticated works accurate tape correction are provided. Correction for absolute length, ii correction for temperature, iii correction for tension or pull, iv correction for sag, and v correction for slope or vertical alignment.
Numerical examples for chain surveying errors in surveying. A steel tape 20 m long standardized at 55 f with a pull of 10 kg find the correction per tape length if the temperature at the time of measurement was 80 f and pull was 16 kg wt. As per plan, the distance between two telephone poles is 356. Survey data is portrayed graphically by the construction of maps, profiles, cross sections, and diagrams.
Random error accidental error occurs in every surveying. What is the corrected horizontal length of a recorded distance ab for the conditions. In any local chaining works, the errors are ignored. Tape correction, sag correction and pull correction. Operator s manual supported torque calibration beam part number. Going through these numericals will actually give you an idea as to how the calculations are done inspite of errors occurring in the chain surveying correction due to incorrect length of chain. Topographic surveying chain and tape survey introduction. First determine if the tape uses metric or english units. In surveying, tape correction refer to correcting measurements for the effect of slope angle, expansion or contraction due to temperature, and the tape s sag, which varies with the applied tension. Tape corrections in chain surveying the constructor.
Surveying is the art of making suitable measurements in horizontal or vertical planes. Latitude departure degree minutes ab s 77 10 e 651. When the vertical angle is used, the formula for slope correction is as follows. Follow techniques that will help detect and eliminatealltheblunders. Surveying problems and solutions manual engineers edge. Operator s manual supported torque calibration beam part. Entering the correct instrument heights, targets heights, and prism offset in the data collector. Factors which influence the use of stylon tape measured distances are limited to the length of the tape, usually. The most common surveying tape will have gradations in feet and hundredths of a foot. These surveys are of high precision and extend over large areas.
What are the errors in taping taping in surve ying methods of measuring with a tape have been dealt with, although it must be said that training in the methods is best undertaken in the field. Applying corrections to the measured length of a line surveying. The shape of the tape will take is known as sag and can be determined mathematically. As per plan, the distance between two telephone poles is. Oct 18, 2004 highway surveying manual page 151 january 2005 chapter 15 construction survey procedures 1501 general in performing construction surveying, preparation is a major part of the operation.
Part number 34320 issue 4 original instructions english. Tension applied to the ends angle of slope weight of tape per unit length combined errors. Setting out a chain line as part of a chain and offset survey to carry out, for example, detail mapping. Jun 28, 2019 for determination of correction for sag, the shape is assumed to be parabolic, instead of catenary. This is the horizontal distance from station k to station l. Solving surveying problems by tape before the modern instruments used to measure angles directly in the field were devised, the tape or rather, its equivalent, the gunters chain was often used. Ken snelgrove lect 7 sept 2407 slide 3 of 7 taping distance errors quanti. For 100ft tapes, from 20 to 30 lb angle, a, or the difference in elevation h between the taped stations. Tapes the metallic tape is a ribbon of waterproof fabric into which small brass or bronze wires are woven to prevent stretching. Entering the appropriate environmental correction factors in the data collector.
The absolute length of a tape is expressed as its standard length. Surveying traverse group example problem 1 b a d c s 77 10 e 651. For 150ft tapes, from 25 to 30 lb for 200ft tapes, from 30 to 40 lb generally, for a heavy 100ft tape weighing about 3 lb that was standardized. The type of surveying that takes into account the true shape of the earth.
Sample problem 5 a heavy 50 m tape having a cross sectional area of 0. Chapter 2 tape correction examples free download as pdf file. Applying corrections to the measured length of a line. Most engineering and property survey are plane survey correction to curvature is made for long strips e. When you take a measurement with a tape along an inclined plane along the natural slope of the ground, obviously, the taped distance is greater than the horizontal distance. Tape correction, sag correction, pull correction and temperature correction. Sag correction zif the tape cannot be supported for its length then it will hang freely under the influence of gravity.
The tape correction used in surveying are as follows. Zdimension height referenced to the mass spherical surface of the earth mean sea level. C p is the tape correction m e is the youngs modulus pa a is the tape area m2 p 1 is the tape tension during measurement n p is the standard pull n example. In practice, this formula correction is rarely used and the field procedure is tailored to accord with the end. Those more commonly used are the heavy steel tape, sometimes called the engineers tape or the highway drag tape, and the metallic tape. During field measurements, the tape was subjected to a tension of 45 n, and was supported at the end points, midpoint, and quarter points, find the correction per tape length due to sag. The correction is positive when the actual length is greater than the nominal length and vice versa. If tape is actually shorter than nominal length then error will be positive because. Let, p0 standard pull p pull applied in the field a crosssectional area of the tape l measured length of line. Not correcting for these effects gives rise to systematic errors, i. Going through these numericals will actually give you an idea as to how the calculations are done inspite of errors occurring in the chain surveying. The length of the traverse legs are measured by chain tape or by stadia method plane table traversing.
Tapes may have several types of scales and gradations. The chain surveying performed by a tape is expected to have some errors due to incorrect tape measurements. Cs l w2 24 n2p2 where, cs tape correction per tape length. Examples on tape corrections errors in chain surveying. Pdf example problems in elementary surveying mouaz. Correction for temperature let t0 temperature at which tape is. It is necessary to apply this correction, since the length of a tape is increased as its temperature is raised, and consequently, the measured distance is too small. When a line is measured with a tape that is too long. Sample problem 6 a 50m steel tape is of standard length under a pull of 5. For chain surveying, at least two men are required, but frequently three people are employed. Plane table survey principles, advantages and disadvantages, equipment, accessories and their uses. Jul 01, 2020 the chain surveying performed by tape is expected to have some errors because of incorrect tape measurements. Properly leveling the survey instrument and targets.
Study the contract plans, special provisions, standard plans, standard specifications, the. The correction, which is difference between the length of catenary and true length is given by. This tape was used in the field to measure a distance that was determined to be. Strength of figures the strength of figure is a factor to be considered in establishing a triangulation system to maintain the. Prior to determining a correction, the surveyor computes. The above expression takes care of sign of the correction also. Proper care in the use, storage, transportation and adjustment of the equipment is a major factor in the successful completion of a survey. During traversing the sides of the traverse are plotted according to any suitable scale. It is given by the formula, c t a t m t ol2 in which c t the correction for temperature, in m. This video explains the corrections that has to be applied to counteract the errors that occur during chaining. Plane table is set at every traverse station in clockwise and anticlockwise direction and the circuit is finally closed.
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