TOPOGRAPHIC SURVEYING 115 



in elevation between B and D. Since the elevation of point 

 C is not desired, its location is not recorded. The distance 

 from B to D is found to be 52 ft., and the second slope is 



recorded . 



52 



The topographer moves forwards to the point D, and the 

 rodman holds the rod at E, the foot of the slope. The top 

 of the rod is below the level line of sight from the topographer's 

 eye, so the rodman "shins the rod," holding it against his 

 body sufficiently high to be intersected by the level line of 

 sight. The rod reading is found to be 11.5 ft. The rodman 

 then measures with the rod the distance from the ground to 

 the point on his body to which the bottom of the rod was 

 raised. This distance, 4.1 ft., is called out to the topographer, 

 who adds it to the rod reading and then deducts the height of 

 the eye. The distance from D to E is found to be 97 ft. This 



slope is recorded . 



97 



STADIA METHOD 



In the stadia method, points are located by means of a 

 transit for the azimuths. The transit is equipped with a level 

 on the telescope, a vertical arc or circle, and stadia wires. The 

 distances and the differences of elevation are determined by 

 stadia measurement. This method is adapted to all kinds of 

 surveys in which a great degree of accuracy is not required. 

 It is the best method of making a general topographical sur- 

 vey of considerable extent, and is especially convenient for 

 preliminary railroad location surveys. The stadia method 

 was officially adopted by the United States Lake Survey in 

 1864. 



PLANE-TABLE METHOD 



In the plane-table method, points located by the plane 

 table are at once platted on the map, which is. thus prepared 

 in the field without the intermediate process of reading ^nd 

 recording angles and distances. This method is well adapted 

 to mapping, especially for filling in the details after the prin- 

 <uoal lines of a survey have been determined by other means. 



