INSTKUCTIONS FOR MAKING PILOT BALLOON OBSERVATIONS 53 



Figure 10.— Plan of tiiangulation of two-theodolite observations where balloon, P, is in a vertical plane 

 through base line, and stations not at the same elevation. 



In triangle APB, angle ABP=e'±d and angle APB=e±e' 

 AP 



h' Ar, h' sin (e± 



-^ or AP= 



sin e'±d sin ie±e') 

 therefore 



d=AP cos e = 

 and 



h=AP sin e 



(sin e±e') 



h' sin {e' :td) cos e 

 sin {e±e') 



h' sin {e' ±d) sin e 



sin {e±e') 



(11) 

 (12) 



Figure 17. — Plan of triangulation for formulas 11 and 12 where balloon P is in a vertical plane through base 

 line and stations are not at the same elevation. 



