gnomon: the part of a sundial that casts the shadow for indicating the time.
golden numbers: numbers denoting the positions of years in the lunar cycle, see article on time and date.
graphometer: type of surveying instrument, see article on the graphometer.
gunner's caliper: a instrument used to take dimensions in gunnery, such as the diameter of cannons and projectiles.
gunner's compendium: an instrument combining several functions required by the gunner, often incorporating the gunner's sight and gunner's level, along with additional elements.