Chapter 5 



THE INFLUENCE OF DISTURBING ACCELERATIONS 



WHEN MEASURING THE FORCE OF GRAVITY AT SEA 



USING A STATIC GRAVIMETER 



K. Ye, Veselov and V. L. Panteleyev 



Gravitational force measurements at sea are of great scientific and practi- 

 cal importance. The perfecting of a method for measuring the force of grav- 

 ity at sea is therefore a pressing problem. 



Up till now the principal method for measuring the force of gravity at 

 sea has been the fictitious pendulum method, the theory of which was put for- 

 ward by Vening Meinesz <^) and other authors. It has been established 

 that to obtain satisfactory results at sea with a pendulum device it is abso- 

 lutely essential to measure the value of the vertical and horizontal accelera- 

 tions in addition to the inclination of the base. 



The static method of measuring gravity at sea has been studied for some 

 fe^v years in the Gravimetric Laboratory of the All -Union Research Institute 

 for Geophysical Methods of Prospecting : in particular, they have constructed 

 prototype instruments and tested them at sea. The results of these tests 

 show that gravity can be measured by marine pendulum devices to an accuracy 

 of the order of a few milligals. 



Some of the basic points in the theory of measurements of this type are 

 examined in paper (1). In the present paper the authors have set themselves 

 the further task of maldng a theoretical examination of certain other points, 

 such as the determination of the equilibrium position of the gravimeter bar 

 from observations taken during its motion, definition of the dynamic coeffi- 

 cient of gravimeters, the effect of inclinations and accelerations on readings, 

 and ways of reducing and compensating these effects. 



The essence of the static method for measuring gravity lies in the crea- 

 tion of a very powerful damping — several hundred times greater than the 

 critical— in the moving part of the gravimeter, as a result of which high 

 frequency accelerations are filtered off (accelerations due to the vessel's 

 motion) and low frequency accelerations (change of gravity accelerations) 

 remain unaltered. 



The equation of motion for a system of this type is solved in Veselov's 



123 



