here is some theory information about levelling used in surveying for elevations or profile drawing etc.

1. LEVELING —THEORY AND
METHODS, AND EQUIPMENT
Dr. Mahmood Arshad
Assistant Professor,
Dept. of Mining Engineering,
Faculty of Earth Sciences and
Engineering,
University of Engineering & Technology,
Lahore.
smarshad@uet.edu.pk
Min-E-240 Surveying
Lecture 6 – Week 4

2. INTRODUCTION
 Leveling is the general term applied to any of the various
processes by which elevations of points or differences in
elevation are determined.
 Leveling results are used to:
 Design highways, railroads, canals, sewers, water supply
systems, and other facilities having grade lines that best
conform to existing topography;
 Lay out construction projects according to planned elevations;
 Calculate volumes of earthwork and other materials;
 Investigate drainage characteristics of an area; (5) develop
maps showing general ground configurations; and
 Study earth subsidence and crustal motion.

3. Terminologies
 Vertical line
 Level surface or equipotential surfaces
 Level line
 Horizontal plane
 Horizontal line
 Vertical datum
 Elevation
 Geoid
 Mean sea level
 Tidal datum (MHW, MHHW, MLW, MLLW
 Benchmark
 Leveling
 Vertical control.

4. Illustration

5. CURVATURE AND REFRACTION
 Horizontal plane departs from a level surface because of
curvature of the Earth.
 Cm = 0.0785K2

6. Dusk and Dawn
 Why sun is red at dusk and dawn??
 Refraction, Rm = 0.011K2
 The combined effect of curvature and refraction,
hm = 0.0675 K2

7. DETERMINING DIFFERENCES IN ELEVATION
 Taping,
 Differential leveling,
 Barometric leveling, and
 Trigonometric leveling (indirect method)
 Electronic measurement of vertical distances (EDM)

8. Differential Leveling
 HI = elev + BS => elev = HI - FS

9. Barometric Leveling
 A change of approximately 1000 ft in elevation will
correspond to a change of about 1 in. of mercury (Hg) in
atmospheric pressure
 Diurnal range
 control barometer, roving instrument

10. Trigonometric Leveling
 The difference in elevation between two points can be
determined by measuring:
 The inclined or horizontal distance between them and (2) the
zenith angle or
 The altitude angle to one point from the other.

11. Trigonometric Leveling – Cont’d
 Take the curvature and refraction into account.
 Homework Exercise. Solve Examples 4.1 and 4.2.

12. CATEGORIES OF LEVELS
 Four categories:
 Dumpy levels,
 Tilting levels,
 Automatic levels, and
 Digital levels
 Two common components:
 A telescope to create a line of sight and enable a reading to
be taken on a graduated rod and
 A system to orient the line of sight in a horizontal plane
 Other types of levels:
 Hand levels,
 Total station instruments
 Electronic laser levels

13. TELESCOPES
 Components:
 Objective Lens
 Negative Lens
 Reticle
 Eyepiece
 Focusing
 Parallex

14. Level Vials
 There are two basic types:
 The tube vial
 Axis of the level vial
 Sensitivity:
• The angle, in seconds, subtended by one division on the
scale and
• The radius of the tube’s curvature
 Coincidence-type tube level
 The circular or so-called “bull’s-eye” version

15. TILTING LEVELS

16. AUTOMATIC LEVELS

17. DIGITAL LEVELS

18. TRIPODS AND HAND LEVEL

19. LEVEL RODS

20. TESTING AND ADJUSTING LEVELS
 Requirements for Testing and Adjusting Instruments
 Nearly level terrain, 200 ft sights in opposite directions.
 Good atmospheric conditions, preferably on cloudy days free of heat
waves.
 No sight line should pass through alternate sun and shadow.
 Place the instrument in shade, or shield it from direct rays of the
sun.
 Tripod shoes are tight and the instrument is screwed firmly.
 Tripod legs well apart and position so that the tripod plate is nearly
level.
 Press the shoes into the ground firmly.
 Adjusting for Parallax
 Testing and Adjusting Level Vials
 Preliminary Adjustment of the Horizontal Crosshair
 Testing and Adjusting the Line of Sight (collimation error)

22. Homework
 Exercise questions in Chapter 4.
 4.15.5 Testing and Adjusting the Line of Sight