**19. Some facts about gravity field**

	- A. The measuring apparatus must be sufficiently sensitive to detect the effect of geology on (g).
	- B. Effective methods must be used to compensate the data for all sources of variation other than the local geology. These corrections will includes chiefly the effect of changing elevation and of crustal heterogeneity on abroad scale.

The interpretation of gravity field is done mainly in two parts:

First solution is sought to the (inverse) potential problem, which Consists in deducing the shape of the source from its potential field these solutions are never unique.

Second, The solutions deduced from (potential field theory) are interpreted in geological terms. This requires some knowledge of the factors which determines the densities of rocks.
