The effect of topographical masses on geoid height determination is described by three terms : the direct topographical effect on gravity, the primary indirect topographical effect on potential and the secondary indirect topographical effect on gravity. Martinec (1998), Sjoeberg and Nahavandchi (1999) and Nahavandchi (2000a) derived different equations to compute these effects. These different approaches for computing the effects over a rugged terrain area (Rocky Mountains) are compared.