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CHaPTER, , , , , , , , , , , , , , , , , , , , , , , , , , B, From the fundamental principle of surveying we know_that on, any area of land to be surveyed, it is always possible to chose two 0 c, points and to measure distance between them. Other points can, be located relative to the 1st line by taking two other, measurements. A, , , , , , , , ¢ The line AB is called base line and all measurements are taken from this line., * Inchain surveying point ‘C’ was located by taking only distance measurements., , * However in compass surveying point ‘C’ is located by taking measurement of angle between BA, & AC & measurement of length AC or angle between AB & BC, BA & AC., , « When the whole area to be surveyed cannot be seen from this one, line, additional lines have to be defined relative to the Ist, using, again two measurements. The points of the junctions of these, lines are called Control Points, and together with the lines, they constitute a framework or control. This method of, , » establishing the control points is called control surveying., , , , , , ¢ In chain surveying the control network consisted of series of, triangles of survey lines., , , , , , , , ¢ In compass surveying points C, D, E, F are established by measuring lengths AC, CD, DE, EF, etc & angles 6,,0,,0,,0, etc., , ¢ This method of establishing points C, D, E, F etc successively by taking linear & angular, measurments is called traversing., , e Where lines AB, BC, CD, DE, EF etc are called traverse lines., , « In traverse surveying the frame work consists of a series of connected lines forming an open, or closed polygon. Accordingly, the traverse is called open traverse or closed traverse., , , , 1. Closed traverse, , ¢ Acclosed traverse starts from a station and closes either on the same station or another station, whose location is already known., , * As shown below in figure (a), the traverse starts from the station A and closes on the same, ~ station. It forms a closed polygon. This type of closed traverse is called as a ldop traverse., , , , DOWNLOADED FROM www.CivilEnggForAll.com

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CIVIL_ ENGINEERING Compass Surveying 47, , ¢ In fig. (b), the traverse starts from the station A and closes at the station E whose location, is also known or established. This type of closed traverse is called a link traverse or connecting, , , , , , , , , , traverse., - E, ™~ E Known Location, D, A®, \ : A \ 7 D, c, \ i, (a) Loop Traverse (b) Link Traverse, Closed Traverse *, Note;, , , , Anerror in a closed traverse can be easily detected and the traverse can be adjusted: and, balanced. me, , , , 2. Open traverse, , e . An open traverse starts from a station A and closés at another station F whose location is, neither known nor established., , ¢ It consists of a series of connected lines., , « An open traverse is generally used in surveying of the area for a road, railway line, canal, etc., , , , , , , , , , , , , , C, , , , Open Traverse:, , , , Note;, , , , An open traverse cannot be properly checked and adjusted. As far as possible, it should be avoided., , , , , , , , Chain Surveying, , , , , , , , , versé Surveying, , , , , , Requires only linear measurements, [hence relatively easier, , , , Requires both nd angular measurements, Hence, requires trained personnel. . :, , , , '2.|The frame work consists of triangles, , Frame.work.consists-of a series of connected lines froming, an open or closed polygon. As the directions of lines are, measured, the polygon can be plotted without constructing, triangles. , , , -| Check lines are required in chain, Surveying, , Check lines are not required because accuracy of the, framework can be checked by the methods of adjustments., , , , 4.)Used when area to be surveyed is, (small, ground is flat and-accuracy, Tequired is low, , , , , , , , Used when area involved is large, and better accuracy is!, required., , , , , , , , tlie lor Emineess, JESIGATE/PSUS,, , are | ‘S MASTER, , , , ‘DOWNLOADED FROM www. CivilEnggForAll.com, , Office: F-126. Katwaria Sarai, New Delhi - 110016, Website: www-iesmaster.org. E-mail: ies_ [email protected], Phone: 011-41013406, 7838813406. 9711853908

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48, , Surveying ~_ CIVIL ENGINEERING, , Note:, , , , Traversing can be done by various methods like compass traverse, plane table traverse,, stadia traverse, theodolite traverse. ee, , , , , , In compass traverse, a magnetic compass is used to determine the angles of the traverse. The, sides of the traverse (called traverse lines) are measured with a chain or a tape., , , , The direction of a line is defined by the horizontal angle which the line makes with a reference line., The fixed line of reference is called a meridian. There are 4 types of meridians used in surveying., , J. True meridian 2. Magnetic meridian, , 3. Grid meridian 4. Arbitrary meridian: ., True Meridian, , The true meridian passing through a point on the earth surface is the line in which a plane, , -passing through a given point and the geographical north and south poles, intersects the, , surface of the earth., It represents the true north-south direction at the place., True meridian at a point can be determined by astronomical observations to the sun or stars., , The true meridians through various stations are not parallel, but converge at the poles., However for small surveys, they aré assumed to be parallel to each other., , True meridian at a point is fixed,, , , , , , A - Rotation axis of earth, Bearing of, line OY | oe] North Pole, , , , , , peey., Observer's °, station, ‘True «> \ Equator, meridan ., Ps, South Pole 1, , , , , , 2., , , , Magnetic Meridian, , Magnetic meridian at.a point is the direction indicated by a freely suspended, balanced magnetic, needle (or a magnetic bar) at that point. This magnetic needle should not be affected by, magnetic forces other than that of the earth for determining the correct direction of the, magnetic meridian., , , , , , ES MASTER x Office: F-126. Katwaria Sarai, New Delhi - 110 016, esata cane Website: www..esmaster.org. E-mail: [email protected] in, IESIGATE/PSUs _ Phone: 011-4101 3406, 7838813406, 9711853908, , , , , , DOWNLOADED FROM www. CivilEnggForAll.com, , sane

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“CIVIL ENGINEERING Compass Surveying 49, , «The freely suspended magnetic needle comes to rest in a position parallel to the line passing, , , , , , , , , , , , , , through the magnetic north and south poles, and-therefore it indicates the direction of the, magnetic meridian at that place., , * The magnetic poles are not fixed in position on the earth. They changé thee positions continually, due to some unknown reasons., , « Hence, magnetic meridian at a point is not fixed it varies with time., , 8. Grid Meridian, , « For survey of a,country, the true meridian passing through the central place is sometimes, taken as a reference meridian for the whole country. Such a reference meridian is known as, , grid meridian. The meridians of all other places in that state are assumed to be parallel to, the grid meridian. =, , « Aline parallel to the grid meridian and passing through the point indicates the directions of, the grid north and south. Like this rectangular grids are plotted on the map., , , Arbitrary Meridian, , ° Arbitrary meridian is the meridian which is.taken in any convenient, arbitrary direction. Any, reference line may be taken as arbitrary-meridian. But usually it is taken in the direction from, a traverse station to a well-defined, permanent point such as a church spire, the chimney, etc., Sometimes, even the first traverse line is also taken as an arbitrary meridian., , ¢ The arbitrary meridian is used for determine the relative directions of various lines in a small, traverse., , , , Bearing of a line is the horizontal angle which it makes with a reference line (meridian)., , Depending upon the meridian, there are 4 types of bearings., , 1. True Bearing, , * The true bearing of a line is the horizontal angle between the true meridian and the line. As, the true bearing of a line does not change with time and can be re-established even after, hundreds of years, hence it is a general practice to use the true bearings for all important, surveys., , , , True-North . — “Magaetic North, , , , ‘True Bearing Magnetic Bearing, of AB: of AB, , », , - (a) B B, , , , , , , , ¢ The true bearing of a line is also called as Azimuth., + Inplane surveying, the true bearing is ineasured from the true north in the clockwise direction., , * The true bearing of a line can be determined by astronomical observations., , = Office: F126. Katwaria Sarai, New Delhi- 110016, wae Website: www.iesmaster.org. E-mail: ies_masterdiyahoo.co.in, seis Eee Phone: 011-41013406, 7838823406, 9711853908, , , , , , , , "DOWNLOADED FROM www. CivilEnggForAll.com

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i. DOWNLOADED FROM www.CivilEnggForAll.com, , 50. Surveying CIVIL ENGINEERING, , 2. Magnetic Bearing, , * Magnetic bearing of a line is the horizontal angle which the line makes with the magnetic, north as shown in the fig(b)., , , , + As the magnetic meridian changes slowly with time, the magnetic bearing of a line also, changes with time. Hence the magnetic bearings are used for small, less important surveys., , * The magnetic bearings are determined with the help of a prismatic compass as a whole circle, bearing and with a surveyor’s compass as a quadrantal bearing., , 3. Grid Bearing, , The grid bearing of a line is the horizontal angle which the line makes with the grid meridian,, of the state., , 4. Arbitrary Bearing, , The arbitrary bearing of a line is the horizontal angle which the line makes with the arbitrary., meridian., , Coe Trt, , , , The bearing of a line is designated in the following systems., , 1. Whole Circle Bearing System, 2. Quadrantal Bearing System, , 1. Whole circle bearing (W.C.B) System, , * The whole circle bearing (W.C.B.) of a line is the horizontal angle. between the line and the, north end of the reference meridian in the clockwise direction. ‘The direction of the line is, indicated by an arrow. The reference meridian is generally represented as a vertical line with, its north end towards the top of the paper., , * The whole circle bearing of a line may vary from 0° to 360°., , ¢ In fig, the whole circle bearings of the line OA, OB, OC and OD are 45°, 150°, 240° and 330°, respectively., , « The whole circle bearing is also called azimuth, and is represented by A., , , , ¢ The whole circle bearing is measured with a prismatic compass., , , , , , , , Whole-circle Bearing, , , , , , E.S MASTER Office: F-126. Ratwaria Sarai, New Delhi - 110016, , Sanat Website: www.iesmaster.org. E-mail: [email protected], , JESIGATE/PSUs. Phone: 011-41013406, 7838813406, 9711853908