THE TOPOGRAPHICAL SURVEY 



31 



All angles should be " doubled " and checked by the needle, 

 and all distances should be checked by stadia. Side 

 shots are obtained by angles and stadia distances. This 

 method of survey is not as accurate as the gridiron method, 

 but the latter in its simplest form is not adapted to park- 



1.L 



V 



1 L 



2 +R 



7 + 00 



+ 00 IB 



jjh + 



Modified Gridiron System of Surueg for Parkways* 



FIG. 8. 



way work. A modified girdiron system, however, may 

 be used when the base-line instead of being one straight 

 line is the broken line of traverse. 



General Remark. In making topographical surveys 

 it is sometimes advantageous to sketch in field. Work of 

 this kind is usually much more accurate, especially when 



