|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.
|gunner's folding rule: a folding rule carrying tables or scales specially adapted for the use of gunners.
|gunner's gauge scales: scales which provide the weight of a sphere (the shot) from a measurement of its diameter; in gunnery these scales were traditionally provided for iron, lead and stone.
|gunner's level: instrument used to set the elevation of a large gun, see article on the gunner's sight and level.
|gunner's rule: see rule.
|gunner's sight: instrument used to elevate and aim a large gun, see article on the gunner's sight and level.
|gunner's sight and level: instrument used to set a large gun to the horizontal, or to elevate and aim it on a target, see article on the gunner's sight and level.
|gunnery instrument: see gunner's compendium.
|hodometer: device for measuring distance by means of a wheel, pushed along the ground, attached to a geared movement with a dial or other form of distance register.
|horary quadrant: quadrant used to tell the time, usually from a measure of solar altitude, see article on the quadrant.
|horizon obliquus: line denoting the local horizon on an astrolabe latitude plate, see article on the astrolabe.
|horizon rectus: east-west line on an astrolabe latitude plate, see article on the astrolabe.
|horizontal dial: sundial where the hour lines are marked on a horizontal surface, see article on the sundial.
|hour lines: the time divisions on a sundial or other astronomical instrument.
|hour ring: the part of a sundial marked with the time divisions, where this part is in the form of a ring or broken ring.
|inclining dial: type of sundial projected as a horizontal dial for a particular latitude, but which can be inclined for use in a range of other latitudes.
|Italian hours: system of hour reckoning, see article on time and date.
|Jacob's staff: name for a cross-staff, especially when used for surveying, see article on the cross-staff.