|gauging rod: measuring stick, usually with a scale to provide a direct reading of volume, such as the liquid content of a barrel, or the weight of a cannonball.
|geographical astrolabe: form of astrolabe, where the lower plate is projected for the earth, while the rete includes the ecliptic.
|geographical planisphere: map of the earth, produced by geometrical projection of a sphere on to a flat surface. Included as the more prominent part of the geographical astrolabe.
|geometrical square: form of quadrant, with sides divided equally and having an alidade at one corner, used for measuring angles in terms of ratios in the manner of a shadow square on the back of an astrolabe.
|globe dial: form of sundial, where the hour lines are on the outer surface of a sphere.
|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.