The different types of leveling
I ) Direct Leveling : Direct measurement, precise, most commonly used;
(1) Simple leveling : One set up of level. To find elevation of points. When the difference of level between two points is determined by setting the leveling instrument midway between the points , the process is called simple leveling.
2. Differential leveling :
Differential leveling is adopted when : (i) the points are at a great difference apart, (ii) the difference of elevation between the points is large, (iii) there are obstacles between the points. To find elevation of non-intervisible points.
This method is called compound leveling or
3. Fly leveling :
When differential leveling is done in order to connect a bench mark to the starting point of the alignment of any project, it is called fly leveling. Fly leveling is done to connect the BM to any intermediate point of the alignment for checking the accuracy of the work. Only back sight and fore sight readings are taken at every set up of the level and no distances are measured along the direction of leveling.
Low precision, to find/check approximate level,
generally used during reconnaissance survey.
4. Precise leveling : Precise form of differential leveling.
5. Profile leveling : Finding of elevation along a line and its cross section.
6. Reciprocal leveling : Along a river or pond. Two level simultaneously used, one at either end.
7. Check leveling
The fly leveling is done at the end of day's
work starting point on that particular day si known as check leveling.
(II) Indirect or Trigonometric Leveling : By measuring vertical angles and horizontal distance; Less precise.
(III) Stadia Leveling : Using tacheometric principles.
(IV) Barometric Leveling : Based on atmospheric pressure difference; Using altimeter; Very rough estimation