alidade
nounUK /ˈælɪdeɪd/
US /ˈælɪdeɪd/
A small tool that helps you see and measure the direction of faraway things.
The surveyor used an alidade to line up the distant tower with the map.
RELATED WORDS
OTHER MEANINGS
2. The rotating pointer on a plane table used to draw lines toward distant objects.
He turned the alidade on the plane table to mark the angle to the hill.
3. A device on an astrolabe or quadrant that pivots to measure angles.
The old astrolabe's alidade swung freely to read the star's height.
4. A sighting bar with a slit and a bead used for aiming instruments.
She looked through the alidade's slit to aim the telescope.