Chap. 7] 



GRAVITATIONAL METHODS 



S23 



rounding terrain exceed the height of the center of gravity of the instru- 

 ment above ground. Then the first two terms in the series of formula 



Table 32 



TERRAIN CORRECTION A 



4b = 0.707(A, + ;i4 - ^« - hs) + h» - h ^d = hi - h^ + hs - hi 

 4c = 0.707(^2 - hi - ht + hs) + hi - h^ 4e = hi - h + h^ - h 



Density: 2.0 Plate = 22.5 Instrument = 125 cm 



+2.0 

 +4.8 



times 



2.36 



0.643 



0.239 



0.082 



0.0186 



3.302 



1.962 1.343| 0.844 



I I 



0.357 



equals 



+ 1.4 

 -3.5 



+0.7 

 -3.1 



+0.1 

 +0.1 



+0.3 

 -0.1 



-0.1 

 



Kxr = Sum c' X - = +2.4 

 K„, = Sum b' X ^ = -6.6 



e' 

 d' 



+0.7 

 +4.6 



-2.7 

 -3.3 



+2.2 +2.1 

 -4.4 +0.6 



Ka = Sum e' X 

 2Kx« = Sum d' X 



= -3.0 

 = -0.8 



+0.7 

 + 1.7 



(7-686) are used, which leads to formula (7-69). As shown in (7-70), it is 

 then more convenient to use the squares of the differences, (h — ^) = H^. 



