Presentation on theme: "Surveying Chain Surveying"— Presentation transcript:
1Surveying Chain Surveying Faculty of Applied Engineering and Urban PlanningCivil Engineering DepartmentSurveying2nd Semester 2007/2008Chain Surveying
2Types of Distance Measurement Measurement Methods ContentsTypes of Distance MeasurementMeasurement MethodsDirect (tapes)Indirect: (EDM, Stadia)Errors and Corrections for Tape MeasurementEDM
3IntroductionOne of the fundamentals of surveying is the need to measure distance. Distances are not necessarily linear, especially if they occur on the spherical earth. In the present subject we will deal with distances in Euclidean (geometric) space, which we can consider a straight line from one point or feature to another.
4Common Methods for Measuring Distances PacingTapingTachometry (required theodolite, and graduated rod)EDM (Electronic Distance Measurement)
5Equipment Used in Chain Surveying Measurement of LinesChainTapesInvar Tapes (more accurate, 65% steel, 35 Nicke)Making Right AnglesOptical PrismOthersRanging RodsArrowsPegsPlumb bobs
9Examples: When use which 1. If you are intending to draw a map or area, horizontal distance and height difference (vertical distance) should be used to enable plan and height information to be drawn.2. If you are to locate points such as a corner of a building or centre line of a road, slope distance and vertical distance are required to enable pigs be located at correct points on site (Layinging Out).
10Methods of Measurement PacingAccuracy 1 : 100TapingAccuracy 1 : 10,000Electronic Distance Measurement (EDM)Accuracy 1 : 10,000 to 1:100,000
11Pacing Practical measure of distance. Don't try to pace out one meter with every step. Walk casually over 100 m counting the number of steps. Work out the length of a casual step and use this instead.Varies with uphill, downhill, and your age.Low accuracyNo equipment needed
12Taping (or chaining)Chaining is applied to measurement with a steel tape or synthetic tape (plastic or fiberglass).All standard in lengths100 m, 50m, 30 m, 20 m.It is fairly quick, easy and cheap, and hence is the most common form of distance measurement.Unfortunately, Chaining is prone to errors and mistakes.For high accuracy, steel tape should be used which is graduated in mm and calibrated under standard temp (20 degree) and tension (5kg). Be careful, easily break.Synthetic tape is more flexible graduated in 10mm
15Some Taping Instruments Measuring wheelsTapes in lengths up to 100 ft
16Taping Procedures ranging rods set up between points A and B from A to B, set zero of tape at Atape unwound towards BA third range rod is “ranged” in at CTape straightened, held tight and read at rod CC marked with a pinfor next bay, tape moved from A and zero set at C and so on
39Setting Out a Line at Right Angles Method 35 m3 m4 m
40Mapping Details Methods of Locating Ground Details Method of Ties: a point is located by measuring two reasonable distance called ties between this point and two points on the chain line (a)Method of Offsets :a point is projected on he chain line and then the distance between the points and its projection (called offset) as well as the distance from the beginning point of the line to the projected point are measured. (b)
50Begin with fresh pageAll measurement should be recordedProceed with booking from the bottom of the page to the top, the records should be recorded in the direction of chainingAll details must be sketched neatly and roughly to scaleAll other chain lines which meet the chain line being measured should be recorded in appropriate place