6. Write station and plus for Pi, PCi, PTi, PC, 

 PT, and PC,. 



7. Find preliminary station and plus, and loca- 

 tion station and plus, for check point A, thus: (a) 

 Compute angles of triangle PiPzA; (b) From the 

 known side and angles of this triangle compute 

 the sides PiA and PaA; (c) The preliminary sta- 

 tion and plus for A is PiPs + PzA; and the loca- 

 tion station and plus for A is PiA. 



8. Having drawn on the map the check line 

 PCsP?, compute the length and bearing of this 

 line. This is done by treating PCdP? as the "miss- 

 ing side" of the closed figure APsPtPePftPrPCs- 

 V.ViA. 



9. Write the alinement notes in the field book. 

 The work of finding the "missing side" in Step 8, 



Just above, involves practically all the operations 

 required to compute the co-ordinates of the chief 

 points of our map from the field notes of the pre- 

 liminary survey. 



Computing from the field notes the rectangular 

 co-ordinates of the chief points of a survey is 

 analogous to computing from the level notes the 

 elevations of the stations on a profile, and hag 

 similar advantages. 



18 



