An algorithm is presented for the computation of gravity terrain corre
ctions from a digitized grid representing topography. Different approx
imations for topography at various distances from the gravity station
are used to make the computation more efficient. For the distant zone
(30 < r < 50 km) topography is approximated using a vertical line mass
distribution. In the intermediate zone (2 < r < 30 km) a segment of a
hollow vertical cylinder is used. The near zone (0.5 < r < 2 km) is a
pproximated using vertical rectangular prisms with sloping upper faces
. A new method is used to compute the correction for the inner zone wh
ich is the digitized square where the gravity station is located. The
gravity effect of topography in the inner zone is calculated from four
triangular prisms with vertices made of the station location and the
comers of the square. The computer program has been tested comprehensi
vely with a regional gravity database from the Southern Uplands of Sco
tland in which all terrain corrections were carried out originally usi
ng the Hammer chart method.