Title SURVEY.PDF ✅

Madan Mohan Malaviya University of Technology, Gorakhpur (U.P.) India Department of Civil Engineering Basic Surveying (BCE -12) Submitted by- Name- ANKIT KUMAR YADAV Course - B.Tech - II (Lateral) Semester - IIIrd Roll. No. -2020012004
Question 1 - What do you understand by chaining and give the name of instruments which are used for chaining. Answer - Chaining :- The process of measuring linear distance with the help of a chain is known as chaining. . The instrument which are used in chaining:- Chain or Tape - For measuring Distance. Pegs - To mark or locate Definite point. Arrow - To mark end point of chain length. Ranging Rod - For stablization of intermediate point between chain length. Cross Staff - To use for perpendicular offset. Optical Square - For perpendicular offset. French Cross Staff - For offset of 450 , 900 , 1350 . Question 2 - Write short notes on the following- Metric Chain, Gunter Chain, Engineer’s Chain, Revenue Chain. Answer - Metric Chain - This is made of galvenised mild steel. The dia. of the wire is 4mm and its length is 20 m or 30 m. Metric chain have 100 or 150 link and the length of one link is 20 cm. The standard pull force of metric chain is 8 kg or 80 N . Standard temp. is 200C. Tolerence limit for metric chain: 10 m Chain ± 2 mm 20 m Chain ± 5 mm 30 m Chain ± 8 mm Gunter Chain:- Gunter's chain (also known as Gunter’s measurement) is a distance measuring device used for surveying. Gunter developed an actual measuring chain of 100 links. The 66-foot (20.1 m) chain is divided into 100 links, usually marked off into groups of 10 by brass rings or tags which simplify intermediate measurement. Each link is thus 7.92 inches (201 mm) long. A quarter chain, or 25 links, measures 16 feet 6 inches (5.03 m) and thus measures a rod (or pole). Ten chains measure a furlong and 80 chains measure a statute miles. Engineer's Chain:- This chain having 100 feet of length and the no. of link is 100. One link length is 1 feet. Mainly this chain is using in Engineer's work. Revenue Chain :- The Revenue chain is 33 ft long and consists of 16 links, each link being 2 1/16 ft long. This chain is mainly used for measuring fields in cadastral survey. Steel band or Band chain. Steel band or Band chain consists of a long narrow strip of blue steel of uniform width of 12 to 16 mm and thickness of 0.3 to 0.6mm. Question 3 - A 20m. chain was found to be 10cm too long after chaining a distance of 1500m. It was found to be 18 cm too long at the end of days work after chaining a total distance of 2900 m. Find the true distance if the chain was correct before the commencement of the work. Solution : For first 1500 metres :- Average error (e) = 0+10 2 = 5 cm = 0.05 cm L' = 20 + 0.05 = 20.05 cm l1 = 20.05 20 × 1500 = 1503.75 m
For next 1400 metres :- Average error (e) = 10 + 18 2 = 14 cm = 0.14 m L' = 20 + 0.14 m l2 = 20.14 20 × 1400 = 1409.80 m Total length (l) = l1 + l2 (l) = 1503.75 + 1409.80 = 2913.55 m Question 4 - The length of a line measured with a 20 m. chain was found to be 250 m. Calculate the true length of the line if the chain was 10 cm. too long. Solution : Incorrect length of the chain (L') = 20 + 10 100 = 20.1 m Measured length (l') = 250 m Hence true length of the line = l' ( L ′ L ) = 250 × 20.1 20 = 251.25 metres Question 5 - The length of an offset is 16 m. and is measured with maximum error of 0.2 m. Find the maximum permissible error in laying off the direction of the offset so that the maximum displacement does not exceed 0.25 mm on the plan to a scale of 1 cm = 50m. Solution : Given : scale (s) → 1cm = 40 cm maximum error (e) = 0.2 m Length of offset = 16 m maximum displacement ≤ 0.25 mm Sin2α = 1 l 2 ( 6.25 1002 s 2 − e 2) Sin α = 1 16 √ 6.25 1002 (502) − (0.2 2) = 1 16 √0.999975 = 0.06245 α = 3.58° Question 6 - Explain the Plans and Maps. Answer - Plans and Map:-As stated in the definition of surveying the objective of measurements is to show relative positions of various objects on paper. Such representations on paper is called plan or map. A plan may be defined as the graphical representation of the features on, near or below the surface of the earth as projected on a horizontal plane to a suitable scale. However, since the surface of the earth is curved and that of the paper is plane, no part of the earth can be represented on such maps without distortion. If the area to be represented is small, the distortion is less and large scale can be used. Such representations are called plans. If the area to be represented is large, small, scales are to be used and distortion is large. Representation of larger areas are called maps. Representation of a particular locality in a municipal area is a plan while representation of a state/country is a map. There is no exact demarcation between a plan and map. We can understand this by considering that the map of a country is made to a very small scale. So that information represented should not exceed to the paper. While the plan of the building is made large and large scale is chosen for that. Therefore the basic difference between plan and a map is that of scale.
Only horizontal distances are shown on a plan or a map. Question 7 - What are the sources of errors in surveying? Explain in brief. Answer - While dealing with any kind of measurements, it is important to identify the possible sources of error. It helps to maintain the accuracy of physical measurement in both fields and labs. There are mainly three possible sources of errors. Instrumental error :-The imperfection or faulty adjustment of the measurement instrument may cause errors. Such errors, produced from the equipment, is known as instrumental error. Example: a long or short tape, an angle measurement instrument without proper adjustment. Personal error :- Error may also arise due to imperfection of human sight in observation and of touch in manipulating instruments. These man made errors are known as personal error. Example: Taking wrong level reading, taking wrong reading of an angle of circle of a theodolite. Natural error :- Variation in natural phenomena is also a possible source of error. Variation of temperature, humidity, gravity, wind, refraction etc. are most common natural phenomena which may cause measurement errors. If they are not properly observed while taking measurements, the results will be incorrect. Example : Length error of tape or chain due to temperature change. Question 8 - What are the sources of errors in measurements with a chain? Identify them as cumulative or compensating. Answer - Sources of errors :- Errors may arise from three sources : (1) Instrumental Error :-Error may arise due to imperfection or faulty adjustment of the instrument with which measurement is being taken. For example, a tape may be too long or an angle measuring instrument may be out of adjustment. Such errors are known as instrumental errors. (2) Personal Error :- Error may also arise due to want of perfection of human sight in observing and of touch in manipulating instruments. For example. an error may be there in taking the level reading or reading an angle on the circle of a theodolite. Such errors are known as personal errors. (3) Natural Error :- Error may also be due to variations in natural phenomena such as temperature. humidity, gravity, wind, refraction and magnetic declination. If they are not properly observed while taking measurements, the results will be Incorrect For example, a tape may be 20 metres at 20'C but its length will change if the field temperature is difference. Systematic errors (Cumulative errors):- A systematic error or cumulative error is an error that, under the same conditions, will always be of the same size and sign. A systematic error always follows some definite mathematical or physical law. and a correction can be determined and applied. Such errors are of constant character and are regarded as positive or negative according as they make the result too great or too small. Their effect is, therefore, cumulative. For example. if a tape is P cm short and if it is stretched. N times. the total error in the measurement of the length will be P.N cm.If undetected, systematic errors are very serious. Therefore : (1) all surveying equipment must be designed and used so that whenever possible systematic errors will be automatically eliminated. (2) All systematic errors that cannot be surely eliminated by this means must be evaluated and their relationship to the conditions that cause them It must be determined. For example, in ordinary levelling, the levelling instrument must first be adjusted so that the line of sight is as nearly horizontal as possible when bubble is centered. Also, the horizontal lengths for back-sight and fore-sight from each instrument position should be kept as nearly equal as possible. In precise levelling, every day the actual error of the instrument must be determined by careful peg test, the length of each sight is measured by stadia and a correction to the result is applied. Accidental Errors (Compensating Errors):- Accidental errors or compensating errors are those which remain after mistakes and systematic errors have been eliminated and are caused by a combination of reasons beyond the ability of the observer to control. They rend sometimes in one direction and sometimes in the other. i.e. they are equally likely