140 



GRAVITATIONAL METHODS 



rcHAP. 7 



7-39 for each of these areas and multiplied by the element number. The 

 sum of these figures is taken and multiplied by the density, provided the 

 latter is uniform around the station. This product is multiplied by the 

 factor given above, which includes the unit effect, gravitational constant, 



Fig. 7-39. Functions of terrain angles ^ (up to 10°) : (1) Vp = tan ^; (2) g (gravity 

 terrain effect) oc i — cos ^; (3) C (curvature terrain effect) a 3 sin ^ — sin'^f-; 

 (4) G (gradient terrain effect) « l — cos^ ^. (After Jung.) 



and scale factor. The terrain effect is always negative. Different types 

 of diagrams which apply to the vertical section through the station and 

 for which, therefore, the elevations may be used directly, have been con- 

 structed by Haalck.^ 



«» Ov. at., 4, 161-178 (1928). 



