Influence the value of g 

Shape of the earth :
(a) At poles : Generally 'g' value is inversely proportional to the radius of the earth ' r' . Due to flattening of the earth at poles ' r' value is minimum and hence 'g' value is maximum.
(b) At equator: Generally 'g' value is inversely proportional to the radius of the earth 'r'. Due to bulging of the earth at equator 'r' value is maximum and hence 'g' value is minimum.

Height: As we move upwards from the surface of the earth, the distance from the centre of the earth increases. Hence 'g' value decreases. 

 

Depth: As we go deep inside the earth, the 'g' value decreases due to effective mass of the earth decreases.

 

Local Conditions: The value of 'g' at a given location is slightly affected by geological deposits, massive concrete ;buildings and topography.