Leveling Florence A. Galeon Assistant Professor U.P. College of Engineering 1 Outline I. II. III. IV. Introduction Definition of Leveling Terms Methods of Measuring Differences in Elevation Common Instruments and Accessories Used in Leveling V. Differential Leveling VI. Sample Problem 2 Leveling It is the process of finding the difference in elevation between two points by measuring the vertical distance between the level surfaces through the points. It is a relatively simple process but an important one in all construction work, in setting machinery and equipment, and in the fabrication of large objects such as ships and airplanes. 3 4 Definition of leveling terms Level Surface – is a curved surface every element at which is normal to the plumbline. Level Line – is a curved line in a level surface all parts of which is equidistant from the center of mass of the earth. 5 Definition of leveling terms Vertical Line – is a line in the direction of a plumb line. Horizontal Line – is a straight line tangent to a level line. It is perpendicular to the vertical or plumb line through the point of tangency. 6 Definition of leveling terms Elevation – is a vertical distance above or below some arbitrarily assumed level surface or datum. Mean Sea Level – is the surface of the sea exactly midway between high and low tides and is regarded as the reference surface to which all elevations are referred. 7 Definition of leveling terms Datum – is a surface of reference coincident or parallel with mean sea level to which all elevations of a given region are referred. Difference in Elevation – is the vertical distance between an imaginary level surface containing the high point and a similar surface containing the low point. 8 9 Methods of Measuring Differences in Elevation 1. Direct (Spirit) Leveling It is the operation of determining the elevation of points some distance apart by a series of set-ups of a leveling instrument along a designated route. 10 Direct Leveling Set-up 11 Methods of Measuring Differences in Elevation 2. Reciprocal Leveling It is the process of determining accurately the relative elevations of two intervisible points a considerable distance apart between which points levels cannot be run in the ordinary manner of leveling. 12 Reciprocal Leveling Set-up 13 Methods of Measuring Differences in Elevation 3. Profile Leveling It is the operation of determining the differences in elevation between points at designated short measured intervals along an established line to provide data from which a vertical section of the ground surface along a surveyed line can be plotted. 14 Sample Land Profile 15 Sample Land Profiles 16 Sample Land Profile 17 Methods of Measuring Differences in Elevation 4. Barometric Leveling It is an operation of determining differences in elevation by observing the atmospheric pressure at different stations by means of a barometer. 18 Different Types of Barometers 19 Different Types of Barometers 20 Methods of Measuring Differences in Elevation 5. Trigonometric Leveling It is a method of determining the difference in elevation between two points by measuring the horizontal or inclined distance between the points and determining the angle between a horizontal line and the inclined line that joins the points. h α d 21 Methods of Measuring Differences in Elevation 6. Borrow-Pit Leveling It is the process of determining the relative elevations of points in borrow-pit excavations for the purpose of calculating volumes of earthwork. 22 23 Natural Borrow-Pit & Profile 24 Common Instruments and Accessories Used in Leveling Engineer’s Level Tilting Level Automatic Level Hand Level Digital Level Leveling Rods 25 Engineer’s & Tilting Levels 26 Automatic Levels 27 Hand Levels 28 Digital Levels 29 Leveling Rods 30 Level & Rod 31 Differential Leveling n Definition: n It is the process of determining the difference in elevation between two points in which a line of level is run from BM₁ to BM₂. 32 Differential Leveling Illustration 33 Differential Leveling Terms Bench Mark (BM) – is a definite point on an object the elevation of which is known. Backsight (BS) – is a rod reading taken on a point of known elevation. 34 Differential Leveling Terms Foresight (FS) - is a rod reading taken on a point the elevation of which is to be determined. Backsight Distance (BSD) – is the horizontal distance from the center of the instrument to the rod on which a backsight is taken. 35 Differential Leveling Terms Foresight Distance (FSD) - is the horizontal distance from the center of the instrument to the rod on which a foresight is taken. Turning Point (TP) – is an intervening point between two bench marks upon which point foresight and backsight rod readings are taken. 36 Differential Leveling Terms Height of Instrument (HI) – is the elevation of the line of sight of the telescope when the instrument is leveled. 37 S A M P L E P R O B L E M 38 39