Tiêu đề NOTES BCEM (U-3).pdf ✅

RUNGTA COLLEGE OF ENGINEERING AND TECHNOLOGY, BHILAI Department of Civil Engineering 1 CIVIL DARSHAN Unit-03 (Surveying & Levelling) SURVEYING-  Definition- Surveying is the art of and science of determining the relative positions of various points or stations on the surface of the earth by measuring the horizontal and vertical distances, angles, and taking the details of these points and by preparing a map or plan to any suitable scale.  Basic principles of surveying- 1. Always work from whole to the part. 2. To locate a new station by at least two measurements (Linear or angular) from a fixed reference points. The area is first enclosed by main stations (i.e. Control stations) and main survey lines. 1. Always work from whole to the part-  According to the first principle, the whole survey area is first enclosed by main stations (i.e.. Control stations) and main survey lines. The area is then divided into a number of divisions by forming well conditioned triangles.  The main survey lines are measured very accurately with precise survey instruments. The remaining sides of the triangle are measured. The purpose of this method of working is to control accumulation of errors. During measurement, if there is any error, then it will not affect the whole work, but if the reverse process is followed then the minor error in measurement will be magnified. 2. To locate a new station by at least two measurements ( Linear or angular) from fixed reference points-  According to the second principle the points are located by linear or angular measurement or by both in surveying. If two control points are established first, then a new station can be located by linear measurement.
RUNGTA COLLEGE OF ENGINEERING AND TECHNOLOGY, BHILAI Department of Civil Engineering 2 CIVIL DARSHAN a. Let A & B are control points, a new point C can be established. b. Following are the methods of locating point C from such reference points A & B. c. The distance AB can be measured accurately and the relative positions of the point can be then plotted on the sheet to some scale. d. Taking linear measurement from A and B for C. e. Taking linear measurement of perpendicular from D to C. f. Taking one linear measurement from B and one angular measurement as∕ ABC g. Taking two angular measurement at A & B as angles / CAB and / ABC. h. Taking one angle at B as / ABC and one linear measurement from A as AC. Diagram of Principle 1 Diagramof Principle 2

RUNGTA COLLEGE OF ENGINEERING AND TECHNOLOGY, BHILAI Department of Civil Engineering 4 CIVIL DARSHAN 3. Compass Surveying- In this type of surveying, a compass is used to determine the direction of survey lines, and the length of survey lines is measured by a chain or tape, or laser range finder. 4. Tacheometric Surveying- Tacheometric surveying is a method of surveying in which the horizontal and vertical distances of relative points are determined without using any sophisticated instruments such as chains, tape, etc. 5. Theodolite Surveying- The theodolite is an instrument that is used to measure horizontal and vertical angles. 6. Photographic and Aerial Surveying- These types of surveying are done by taking photographs from elevated ground stations. 5. Classification based on the methods of Survey- 1. Triangulation Surveying- Triangulation is a method of surveying that measures the angles in a triangle formed by three survey control points. 2. Traverse Surveying- It is also a well-known method of surveying. A traverse is a series of connected lines whose lengths and directions are measured with the help of an angle measuring instrument and tape or chain, respectively. LEVELLING-  Definition- The technique of determining the relative altitude of a point on the earth's surface below the earth's surface is called levelling.  Principle Of Levelling- The principle of levelling is to obtain a horizontal line of sight at which the vertical distance of a point above or below this line of sight is found.  The Purpose of Levelling- 1. Find the heights of the given points in relation to the given data. 2. Establishing points at given heights or at different heights in relation to given or considered data.  Technical Terms- 1. Station- Any points where the staff is held and the reading taken during the process of levelling is called stations. 2. Datum- It is an arbitrary level surface from which elevation of points may be referred. In India mean sea level is considered as datum of zero elevation, which is situated at Karachi.