Surveying annai mathammal sheela engineering college. A traverse is developed by measuring the distance and. Fore bearing and back bearing the bearing of a line, whether expressed in wcb system or in q. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Problem 3 enter the field book according to the following field notes. What is fore bearing and back bearing in surveying is discussed with examples. Both bearings and azimuths refer to the relationship of the given line to a reference meridian, usually one of many interpretations of north.
Chain surveying is the type of surveying in which only linear measurements are made in the field. Bearing surveying traverse latitudes and departures example. Magnetic bearing of a survey line at any place a remains constant b changes systematically. The angle measured in the direction of survey line from starting survey station to the next station is called fore bearing. Add 180 degrees to the compass bearing to your destination if the bearing is less than 180 degrees. Fore bearing is the bearing of the line in the forward direction of surveying. The name prismatic compass is given to it because it essentially consists of a prism which is used for taking observations more accurately.
Below are the bearings observed in a traverse survey problems on. It starts at a point of known position and terminates at a point of unknown position. For each survey line in the traverse, surveyors take two bearings that is fore bearing and back bearing which should exactly differ by 180 if local attraction is negligible. A prismatic compass is a navigation and surveying instrument which is extensively used to find. It is the angle which is measured directly from the survey station point and other station in the same path of conduct of survey. The magnetic bearing of a line measured clockwise from the north. The first compass bearing we need to take at the lake is from our unknown location to our cabin on the far shore. The bearing of a line measured in direction backward to the direction of the progress of survey is called the back bearing b. Surveying traverse almost all surveying requires some calculations to reduce measurements into a more useful form for determining distance, earthwork volumes, land areas, etc. Classification of bearings surveying civil engineering. Traverse surveying is a popular method of surveying. Rule out a page of level book and enter the readings. Reduced bearing rb or quadrantal bearing qb fore bearing fb or forward bearing fb back bearing or backward bearing bb calculated bearing.
Then two bearings of least discrepancy is selected in such a way that the difference of them is closest to 180 the mean value is obtained by adding half of the correction to fore bearing value and half to back bearing. More specifically, surveying is the science of making measurements, relative to known or assumed datums and standards, and. Survey records and computations such as field notes, level books, field books. It is a point on which fore sights and back sight are taken.
Some important things to remember about the use and care of the equipment are as follows. The formula used to calculate the back bearing of line b. Back bearing of previous line fore bearing of next line. Fore bearing and back bearing the bearing of a line measured in the forward direction of the survey lines is called the fore bearing f. Also, local attraction is explained which often is asked in exams. If the bearing of line ab is measured from a towards b, it is known as forward.
Civil engineering surveying and leveling 362 important mcq pdf. The magnetic bearings of the lines are measured by prismatic compass and the distances of the lines are measured by chain. Book and calculate horizontal and vertical angles from theodolites readings. Definition of surveying in general, surveying is performed to determine the relative location or positioning of points on or near the earths surface. This concept is applicable in surveying field of study. What is fore bearing and back bearing in surveying with. Your field book shall be kept neat and orderly as it will be collected. In many applications, including descriptions, plats, and maps, the direction of a given line is expressed as a bearing or azimuth. After finding that line we apply the correction to the bearings of the other lines. Temporary adjustments in compass survey using a prismatic compass. In my previous article, i discussed different types of bearings in compass surveying.
Fore and back bearing a line may be expressed by two bearings observed from the either end of the line. Fore bearings and back bearings between the traverse. For example, if the bearing to your destination is 50. For example, if the bearing to your destination is 200 degrees, the back bearing is 20 degrees 200 180 20.
This article includes the definition of traverse surveying along with its classification, errors in traversing, checks, the completed method of traversing and plotting of traverse survey. In civil engineering surveying, bearing is very important to get the direction of a survey line. For example, if the bearings of the lines ba and ac are given, then to find angle at a, the bearings of ab must be obtained. Traverse surveying definition, types, methods, checks. Then, starting from this adjusted line, the fore and back bearing of other lines are corrected. Calculation of angles from bearings compass surveying. Surveying lab manual dronacharya group of institutions. Fore bearing and back bearing is explained with solved examples from previous year competitive exams like gate, ies. Basic static load basic static load, cor, is given in the bearings catalogues for every size and it is taken in consideration when the bearing is stationary, has slow oscillations, low speed n fore bearing is the bearing of the line in the forward direction of surveying. Also, if the traverse closes back on itself the sum of all the calculated differences easting must sum to zero and the sum of all the differences. This book, produced for use by skf distributors and customers, should prove of practical value to mechanics, maintenance superintendents and anyone.
Direction of survey and location of the north however guides the relation between back bearing and fore bearing based on the reference point. The bearing of a line is its orientation with respect to grid north. The bearing we end up with represents the angle between a line from magnetic north to our location, and a. Compass surveying abhilashaps free download as powerpoint presentation. Below are the bearings observed in a traverse survey conducted with a prismatic compass at a. Fore bearing and back bearing confusion, please help. The use of levels and total stations is illustrated by a series of practical examples. This type of survey can be used to measure large areas with. If we find such line then that means the two end stations of that line are free from any local attraction. What is fore bearing and back bearing in surveying with examples. It is the angle measured from the next station point to the previous station point from which the fore bearing is determined.
A surveying operation carried out to determined the elevation of points or to find. B system, differs according as the observation is made from one end of the line or from the other. The bearing we end up with represents the angle between a line from magnetic north to our location, and a line from our. Aait, department of civil engineering 2 lecture note.
Civil engineeringsurveying and leveling 362 important mcq pdf. Surveying is an art of determining the relative positions of various points on, above or below. Difference of fore bearing and back bearing is always is equal to 180 degree which. The principle of compass surveying is traversing, which involves a series of connected lines. The fore bearing and back bearing conducted on a line ab. 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.
Express both the bearings as if they are measured from the point where the lines intersect and then apply the above rule. In this article, we will discuss in brief different designations given to the bearings depending on measurement of angles. The branch of surveying in which direction of survey line are determine by a compass and their length by a chain or tape is called compass surveying. Reduced bearing rb or quadrantal bearing qb fore bearing fb or forward bearing fb. Introduction to cogo also used in the basic surveying class history of cogo, cogo languages, seven prominent cogo functions. The angle made by the survey line with reference to arbitrary meridian is known as arbitrary bearing. Surveying has to do with the determination of the relative spatial location of points on or near the surface of the earth. So, whatever the way we have recorded these in our field book field book was. Understanding forward and back bearings taking a forward bearing. In this section, we will examine the back and fore bearing. To measure bearings of a closed traverse by prismatic compass and to adjust. Learning objectives at the end of this chapter, students will be able to.
As shown in fig4 above, the bearing taken in the direction of ab is called as fore bearing and the measurement taken in the direction of ba forms the back bearing as shown in the figure4. The definition of the whole circle bearing along with the measuring formula and example is discussed below. It is the bearing of the survey line taken from the forward. Bearing self study guide expanding your knowledge of bearings and related components.