|surveying instrument: surveyors used instruments to take bearings, elevations, distances and other associated measures, as well as, for example, laying out plans and drawing topographical surveys. Included are such instruments as the surveying compass, surveying quadrant, surveying rod, surveying staff, surveyor's cross, surveyor's line, surveyor's square and theodolite. Surveying instruments also include compound instruments embodying several such functions.
|surveying instruments: see surveying instrument.
|surveying quadrant: quadrant used for land surveying, usually for measuring altitude and azimuth.
|surveying rod: an instrument used by surveyors for taking distances and other associated measurements.
|surveying staff: an instrument used in surveying to measure elevations.
|surveying staffs: see surveying staff.
|surveyor's cross: instrument for establishing right-angled lines of sight, by means either of open sights set at the ends of an equal-arm cross or slits in a cylinder.
|surveyor's line: a long string or rope used to measure distances for surveying.
|surveyor's square: another name for a surveyor's cross.
|theodolite: surveying instrument for measuring horizontal angles, and perhaps vertical angles, see article on the theodolite.
|theodolite and sundial: an instrument combining the functions of a sundial and a theodolite.
|throne: part of an astrolabe, connecting the instrument to the suspension shackle, see article on the astrolabe.
|triangulation: surveying technique involving the measurement of a baseline, the location of other stations by taking angles from either end, and perhaps the extension of the survey through the addition of further triangles.
|triangulation instrument: instrument with three jointed arms with scales for surveying or range-finding, see article on the triangulation instrument.
|trigonus: triangular element in the type of altitude dial known as the 'organum Ptolemai'.
|tripod base: base of a tripod (three-legged support) on which to stand an instrument.
|tripod legs: legs of a tripod (three-legged support) on which to stand an instrument.
|tropic of Capricorn: line of geographical latitude and corresponding line of declination coinciding with the sun's position at the autumnal equinox, its most southerly position in the sky.
|tympanum: Latin name (plural tympana) for a latitude plate of an astrolabe.
|unequal hours: system of hour reckoning, see article on time and date.