98 STADIA AND PLANE-TABLE SURVEYING 



Form of Stadia Notes. A regular transit book is used for 

 keeping notes in stadia surveying, its arrangement being shown 

 herewith. The letters A and B in the first column signify 

 the points where stadia readings were taken, and the marks 

 designate instrument stations. The vertical angles are 

 prefixed with + or , according as they are angles of elevation 

 or depression. The columns headed Hor. Dist. and Elev. are 

 filled out in the office. The notes to the right of the double 

 line are made on the right-hand page of the actual notebook. 



Stadia Reduction Tables. The work of reducing the notes 

 in stadia surveying is conveniently done by means of the accorrf- 

 panying tables. In these tables are shown the horizontal 

 distances and differences of elevation for various vertical 

 angles, for the stadia constant 100 and for the rod reading 1. 

 Thus, in the column headed Hor. Dist. is given the value of 

 100 cos 2 V or d\, and at the bottom of the page the value 

 * cos V or id for i= .75, 1.00 or 1.25 may be found. From this, 



Similarly in the column headed Diff. Elev. are given values 



100 sin 2V 



of - , or w, and at the bottom are found values of 

 2 



sin V or i v . From this, 



EXAMPLE. The stadia rod reading is 3.96 ft., the vertical 

 angle is 10 26'; 5 = 100, and i= 1.00. Find d and v. 



SOLUTION. From the table dj. for 10 26' = 96.72, and 

 rf = .98. Hence, d = 96.72X3.96 +.98 = 383.99 ft. Likewise, 

 n = 17.81 and ^ = .18. Finally, = 17.81X3.96+. 18 = 70.71. 



