Local attraction in compass surveying may exist due to a incorrect levelling of the magnetic needle b loss of magnetism of the needle c friction of the needle at the pivot d presence of magnetic substances near the instrument ans. Oct 30, 2011 local attraction methods for correcting the bearings affected by local attraction. As already stated in the last section, surveying which involves a series of connected lines is known as. Local attraction methods for correcting the bearings affected by local attraction. Surveying to find local attraction and correct bearing in hindi. The routine of chaining and offsetting is the same as in chain survey compass surveying is not recommended for areas where local attraction is suspected due to the presence of magnetic substances.
Earth is the largest magnetic field and while compass surveying local attractions like electric wires, iron, steel etc. Dip inclination of the needle with the horizontal is called dip of the needle. Compass surveying is recommended when the area is large, undulating and crowded with many details. If the surveying area is large, chain surveying is not adopted for surveying rather compass surveying. Local attraction method of correction for traverse first method sum of the from civil. It may be noted that the included angle is not influenced by local attraction as both readings are equally affected. While compass surveying, the magnetic needle is sometimes disturbed from its normal position under the influence of external attractive forces. Methods for correcting the bearings affected by local attraction. Compass surveying magnetic declination the angle that a magnetic meridian makes with the true meridian. Advantages of compass surveying equipment used are light and easy to carry observations are made comparatively fast bearings taken at one station are independent of those taken in another station. Feb 04, 2018 if no line has the difference of 180 then watch this.
Introduction to compass traversing, surveying and levelling. To find out this we have to look for a line where the difference between the fore bearing and the back bearing is exactly equal to 180 degrees. Line or plane passing through geographical north pole and geographical south pole magnetic meridian. Local attraction when a magnetic needle is disturbed from its normal position due to influence of external forces such as electric current or magnetic substances, local attraction is said to have occurred. Local attraction in compass surveying may exist due to. Nov 06, 2017 local attraction in compass surveying may exist due to a incorrect levelling of the magnetic needle b loss of magnetism of the needle c friction of the needle at the pivot d presence of magnetic substances near the instrument ans. This is because that these magnetic compass is influenced by other magnetic objects at that locality such as wires carrying electric current, rails, steel and iron. Unless the local attraction at a place is found out and corrected, the bearings. Civil engineering surveying important mcq pdf all exam. Magnetic dip the vertical angle which the magnetic needle makes with the horizontal due to uneven magnetic attraction form the magnetic poles. Local attraction in compass surveying may exist due to a incorrect levelling of the magnetic needle b loss of magnetism of.
Compass surveying surveying is concerned with the relative location of points on, above or below the surface of the earth. Local attraction affects all bearings observed at a point by equal. If the difference of the two differ by 180o then there is no local attraction and if not then exist local attractive forces and either of the two will be affected by local attractive forces. Cross staff is an instrument used for a measuring approximate horizontal angles b setting out right angles c measuring bearings of the lines d none of the above ans. Calculation of angles from bearings compass surveying. Local attraction method of correction for traverse first method sum. Surveying and levelling multiple choice questions and answers.
Below are the bearings observed in a traverse conducted with a prismatic compass at a place where local attraction was suspected. Disadvantages accuracy of angular observations is low. Local attraction in compass surveying may exist due to a. The deflection of a magnetic needle from its true position due to the presence of magnetic influencing material such as iron ore, magnetic rock, underground pipeline, electric cables, iron pipes, electric poles in its vicinity is called local attraction.
Each topic introduced is thoroughly described, the theory is rigorously developed, and a large number of numerical. Compass surveying is not recommended for areas where local attraction is suspected due to the presence of magnetic substances like steel structures, iron ore deposits, electric cables conveying currents, and so on. It is not possible to check the consistence of angles and distance measurement. The magnetic needle is disturbed from its normal position if it is under the influence of external attractive forces called the sources of local attraction. If local attraction is detected in a compass survey observed bearings may be corrected by any one of the following two methods. Essential features of compass sight vanes which defines the line of sight in the direction of the sn points of the compass box.
Dec 30, 2017 compass surveying is the branch of surveying in which the position of an object is located using angular measurements determined by a compass and linear measurements using a chain or tape. Local attraction is the phenomenon by which the magnetic needle is constantly prevented to point. Such a disturbing influence is known as local attraction. Sep 08, 2012 1 in first method we have to find out the stations where no local attraction exists. Compass surveying is used in following circumstances. Compass surveying is a type of surveying in which the directions of surveying lines are determined with a magnetic compass, and the length of the surveying lines are measured with a tape or chain or laser range finder. Local attraction in compass surveying may exist due to a incorrect levelling of the magnetic needle b loss of magnetism of the needle c friction of the needle at the pivot. The external forces are produced by sources of local attraction which may be current carrying wire magnetic materials or metal objects. Land surveyor interview questions and answers pdf surveying. A freely suspended and properly balanced magnetic needle is expected to show magnetic meridian.
This can be used for surveying the land area with undulations which is crowded and large. Introduction to compass surveying and their components, types of compass, errors in compass, corrections for local attraction, principles and procedures. It starts at a point of known position and terminates at a point of unknown position. Local attraction in compass surveying elimination methods. Local attraction with remedies compass surveying surveying. Let a be the interior angle required at a station, p be the f. The imaginary level surface with reference to which vertical distance of the points above or below are measured, is called datum surface. Line ab bc cd da fb n66015e s50015e s38030w n53015w bb s 640 w n 470 w n 370 30e s 530 15e. This is because that these magnetic compass is influenced by other magnetic objects at that locality such as wires carrying electric current, rails, steel and iron structures, steel tapes etc. The magnetic bearings of the lines are measured by prismatic compass and the distances of the lines i. Professionals, teachers, students and kids trivia quizzes to test your knowledge on the subject.
The compass calculates bearings of lines with respect to magnetic needle. Local attraction affects all bearings observed at a point. Aline or plane passing through geographical north pole and geographical south pole magnetic meridian. If we find such line then that means the two end stations of that line are free from any local attraction.
This volume is one of the two which offer a comprehensive course in those parts of theory and practice of plane and geodetic surveying that are most commonly used by civil engineers. Local attraction in compass surveying may exist due to, options are. Local attraction method of correction for traverse first. Compass traversing surveying notes, advanced surveying. When the magnetic needle is suspended freely and balanced properly. Methods for correcting the bearings affected by local. Hence errors in angular measurement do not accumulate. Also indicate the stations free from local attraction. A incorrect levelling of the magnetic needle, b loss of magnetism of the needle, c friction of the needle at the pivot, d presence of magnetic substances near the instrument, e, leave your comments or download question paper. Engineering interview questions,mcqs,objective questions,class lecture notes,seminor topics,lab viva pdf. A compass shows the direction of the magnetic meridian on the principle of magnetism. However, local objects like electric wires and objects of. In the quadrantal bearing system, a whole circle bearing of 293 30.
Civil engineering surveying questions and answers pdf. Components and functions compass box a box in which all the components of compass are housed pivot a pointed support for the magnetic needle, prepared from hard steel magnetic needle a thin magnetic plate, indicates north direction. These sample surveying objective type questions are framed by experts. However, local objects like electric wires and objects of steel attract. Compass surveying principles use of prismatic compass, measurement of bearings, conversion of bearings, local attraction, correction of compass traverse. Local attraction at any particular place can be detected by observing both fore and back bearing of the survey line. The compass is generally used to run a traverse line.
Compass surveying is a type of surveying in which the directions of surveying lines are determined with a magnetic compass, and the length of the surveying lines are measured with. The branch of surveying in which direction of survey line are. If the location of two points is known, a third point may be located by. Keuntungan menggunakan metode compass survey ini yaitu alat yang digunakan ringan dan mudah dibawa, pengukurannya lebih cepat, dan setiap bearing tidak terganggu pengukuran sebelumnya. Sep 18, 20 compass surveying is recommended when the area is large, undulating and crowded with many details. This article provides a note on local attraction along with its remedies and examples.
May 11, 2020 introduction to compass traversing, surveying and levelling agricultural engineering notes edurev is made by best teachers of agricultural engineering. Prismatic compass surveying pdf notes download compass surveying prismatic compass compass traversing important definition true meridian. Normal tension is that pull which a is used at the time of standardising the tape b neutralizes the effect due to pull and sag c makes the correction due to sag equal to zero d makes the correction due to pull. Local attraction compass surveying hello, local attraction. It therefore becomes necessary to start from known points on a line. Dec 15, 2017 compass surveying is mainly employed in areas that is free from local attraction. Prismatic compass surveying pdf notes expert civil. Surveying and levelling multiple choice questions and. There may be local attraction due to the presence of magnetic substances near the station. Compass surveying is not recommended for areas where local attraction is suspected due to the presence of magnetic substances like steel structures, iron ore deposits, electric cables. Compass surveying is mainly employed in areas that is free from local attraction. Watch easy method to find the value of corrected angle free from local attraction as well as bearing also.
The first volume covers in 24 chapters, the most common surveying operations. Professionals, teachers, students and kids trivia quizzes to. Local attraction method of correction for traverse. Such a disturbing influence is called as local attraction. Compass surveying is not recommended for areas where local attraction is suspected due to the presence of magnetic substances like steel structures, iron ore deposits, electric cables conveying current, and so on. In such a situation magnetic needle does not point towards north south. The surveyors compass was formerly much used in land surveying, but now it is. Compass surveying is used in following circumstances,traverse surveying definition, types, methods, checks,compass traversing,compass traversing practical,compass traverse survey pdf,principle of compass surveying,local attraction,traverse surveying pdf,plane table. May 10, 2015 also indicate the stations free from local attraction. Sep 05, 2016 compass surveying is not recommended for areas where local attraction is suspected due to the presence of magnetic substances like steel structures, iron ore deposits, electric cables, and so on. Mcq quiz on surveying and levelling multiple choice questions and answers on surveying and levelling mcq questions quiz on surveying and levelling objectives questions with answer test pdf for civil engineering. Any magnet attracting material, when is brought near to the compass needle, needle will deflect from the true magnetic north. Oct 22, 2016 there may be local attraction due to the presence of magnetic substances near the station. Detecting local attraction of construction civil engineering.
Local attraction in compass surveying quantity takeoff. When the magnetic needle is suspended freely and balanced properly, unaffected by magnetic substances, it indicates a direction. What are the factors affecting selection of contour interval. Every bearing at each of station can be observed by conducting the compass survey by letting the needle to float. Land surveyor interview questions and answers pdf 41. In a closed traverse, where local attraction is not suspected i. Advantages of compass surveying equipment used are light and easy to carry observations are made comparatively fast bearings taken at one station are. A incorrect levelling of the magnetic needle, b loss of magnetism of the needle, c friction of the needle at the pivot, d presence of magnetic substances near the instrument, e. Sources of error in compass civil surveyor course in. Sources of error in compass civil surveyor course in islamabad. Kelemahan metode ini yaitu pembacaan tidak teliti dan adanya pengaruh medan magnet setempat atau local attraction.
This inclination of the needle with the horizontal is known as dip of the magnetic needle. Isogonic lines an imaginary lines passing through places having the same magnetic. Local attraction affects all bearings observed at a point by. Easiest method to find local attraction and find correct. We are committed to serving our clients by always presenting a professional, responsive approach and by maintaining the highest level of integrity and customer satisfaction.
We know that even if the local attraction is present at every. Aait, department of civil engineering 2 lecture note. Introduction to compass traversing, surveying and levelling agricultural engineering notes edurev notes for agricultural engineering is made by best teachers who have written some of the best books of agricultural engineering. Such survey does not require the formation of a network of triangles.
Plane table survey principles, advantages and disadvantages, equipment, accessories and their uses. This document is highly rated by agricultural engineering students and has been viewed 229 times. A prismatic compass is a navigation and surveying instrument which is extensively used to find out the bearing of the traversing and included angles between them, waypoints an endpoint of the lcourse and direction. Surveying is the art of determining the relative positions of distinctive features on the surface of the earth or beneath the surface of the earth by means of measurements of distances, directions and elevations.
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