Classification of leveling
1. Different leveling:
It is the operation of leveling to determine the elevations of points. Some distance a part or to establish bench marks.
2. Check leveling:
It is the operation of running levels for the purpose of checking the series of levels, which have been previously fixed. At the end of each day’s work, a line of level is run, returning to the starting point of that day with a view to check the work done on that day.
3. Profile leveling:
It is the operation in which the object is to determine the elevation of points at known distance apart along a given line, and thus to obtain the accurate out line of the surface of the ground. It is called the longitudinal leveling or sectioning.
4. Cross sectioning:
It is the operation of leveling to determine the surface undulation or outline of the ground transverse to the given line and on either side of it.
5. Reciprocal leveling:
It is then method of leveling in which the difference in elevation between two points, accurately determined by two sets of observation when it is not possible to set up the level midway between the two points.
6. Barometric leveling:
It is the method of leveling in which the altitudes of points are determined by means of a barometer, which measures atmospheric pressure.
7. Hypsometry:
It is the method of leveling in which the heights of mountains are found by observing the temperature at which water boils.
8. Trigonometric leveling:
It is then process of leveling in which the elevations of points are computed from the vertical, angles and horizontal distance measured in the field.
Steps in Leveling:
When the level is set up and correctly leveled, the lines of collimation will be horizontal. When the telescope is rotated about its vertical axis, it will revolve in a horizontal plane known as the plane of collimation. Therefore all staff readings taken with the telescope will be vertical measurements made downwards from this plane. There are two essentials steps in leveling.
- To find the elevation or R.L. of the plane of collimation (H.I) of the level by taking a back sight on a bench mark.
- To find the levitation of R.L. of any other point by taking a reading on the staff held at the point.
Height of Instrument (H. I.) = R.L. of the plane of collimation
= R.L. of B.M. + B.S.
R. L. of point = H.I.-F.S.
= H. I. – I.S.
= R.L. of B.M. + B.S.
R. L. of point = H.I.-F.S.
= H. I. – I.S.
It is the necessary that after every back side. [However many intermediate sight may be], there must be a foresight. Leveling should always commence from a permanent common bench mark and end on a permanent bench mark.