ANGULAR SURVEYING 



37 



the end of the line, or also at the intermediate point, in which 

 event the bearing of the line must be corrected by determining 

 the angle by which the needle is deflected by the disturbing 

 influences. This can be done by taking the foresight and 

 backsight of a line formed by joining an outside point having 

 no local attraction with the beginning or end of the line whose 

 bearing is required. 



Form for Compass Field Notes. In Fig. 4 is shown a con- 

 venient form for keeping the notes of a compass survey. The 

 left-hand half of the diagram represents the left-hand page of. 



FIG. 5 



the notebook; the right-hand half, the right-hand page. The 

 notes are supposed to apply to the field ABCDE, Fig. 5. The 

 corner, or station, A is the starting point of the survey, the 

 courses being run from A to B, from B to C, etc. The notes 

 read from bottom to top. Opposite the letter denoting a cor- 

 ner is given the bearing of the course running from that corner 

 to the following one, in the order in which the survey was 

 made. For instance, the bearing N 43 20' E horizontally 

 opposite A denotes the bearing of the course AB. The num- 

 ber opposite a corner in the column of distances is the distance 

 of this corner from the preceding one. 



