Rise and Fall Method

What is Rise and Fall Method?

Rise and Fall method is one of the method of Dumpy level / Auto level Surveying. Rise and Fall of levels are main aspects in this method. 

The rise and fall method is the method of calculating the difference in elevation between consecutive points in levelling work. Some of the points you have to know before starting numerical are: 

Back sights: The first reading after seeing the instrument is called back sights.

Fore sights : The last reading of survey is called fore sights.

Intermediate Sights : The reading points between Back sights and Fore sights called as Intermediate sights.

Example:

The following staff readings were taken with a Dumpy Level and 4m staff. The first reading on a B.M. of R.L. 300m. Rule out a page of field book and calculate R.L.'s of all the points by Rise and Fall Method.

Readings are : 1.235, 2.005 , 1.875, 0.960, 0.380, 1.640, 2.840 , 1.750, 1.930, 2.150, 2.370, 2.460

The instrument was shifted after 4th, 7th, and 10th  reading.

Solution :

Arithmetic Check :

∑ B.S. - ∑ F.S                        = ∑ Rise - ∑ Fall                        = ∑ Last R.L. - ∑ First R.L.

= 5.735 - 8.41                        = 1.045 - 3.72                               = 297.325 - 300.00

= -2.675                                 = -2.675                                        = - 2.675

Answer is successfully verified.