CHAPTER VIII 



LEVELING PRACTICE 



Differential Leveling. Differential leveling is the name 

 given to the process of finding the difference of elevation of 

 two or more points at some distance from each other, with- 

 out reference to intermediate points except those required 

 temporarily in carrying a line of levels between the points 

 whose difference of elevation is required. Differential 

 leveling is like profile leveling, except that elevations are 

 not taken at regular intervals on the surface. It is desir- 

 able, however, to make the .sights or the distances between 

 the instrument and rod of equal length, as this tends to equal- 

 ize errors which may exist in the adjustment of the instru- 

 ment. 



Profile Leveling. Profile leveling is for the purpose of 

 obtaining the elevations of the surface of the ground. It is 

 especially important in this connection, as profile leveling 

 is required in the laying out of land drainage systems. 



Leveling. The process of leveling, or in other words the 

 performance of the field work in determining the elevation 

 of points on the surface of the ground, is comparatively 

 simple, yet it is highly important that the work be done 

 accurately and that a full record be made of the work. 



To run a line of levels, a bench mark, or a permanent point 

 of reference, should be chosen from which a start is made. 

 The importance of the bench mark is all the more magnified 

 with an increase in the size of the system of levels. If the 

 elevation of the bench mark is not known, it must be assumed. 

 For convenience it is usually taken as 10, 20, or 100 feet, 



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