We analyze gravitational effects of distant topographic and bathymetric relief beyond the (earth-centered) angular distance of [Formula: see text] (i.e., beyond the outer limit of the Hayford-Bowie zone O, or approximately [Formula: see text]) using a spherical earth model. Our results support current procedures that neglect distant relief effects for most local gravity surveys but show their potential importance for continental- and global-scale surveys. The distant relief can produce horizontal gradients as large as [Formula: see text] [Formula: see text]. In mountainous areas, the gravitational effect of the distant relief is significant, even for local surveys, although the vertical gradient of the distant relief effect never exceeds [Formula: see text] [Formula: see text] on the earth’s surface.

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