What does a graphometer measure?
A graphometer is a topographical instrument used to measure horizontal angles. It is made up of a circle graduated in 360° degrees.
Who invented the graphometer?
Philippe Danfrie
Graphometer/Inventors
Philippe Danfrie was an engraver, printer, and inventor, best known for the invention of the graphometer, which is a surveying instrument operated on the principles of the theodelite. It became the standard surveyer’s tool and remained in widespread use well into the 19th century.
What is an Alidade used for?
NMAH | Surveying & Geodesy | Alidade. The term alidade can refer to the sighting mechanism of any instrument used for surveying or navigation. In this catalog the term refers to the sighting mechanism used with a plane table for topographical work—that is, for mapping the surface features of the earth.
How does a Groma work?
The groma or gruma was a Roman surveying instrument. It comprised a vertical staff with horizontal cross-pieces mounted at right angles on a bracket. Each cross piece had a plumb line hanging vertically at each end. It was used to survey straight lines and right angles, thence squares or rectangles.
What is the use of plane table surveying?
A plane table (plain table prior to 1830) is a device used in surveying site mapping, exploration mapping, coastal navigation mapping, and related disciplines to provide a solid and level surface on which to make field drawings, charts and maps.
Why horse hair is used in alidade?
Two types of alidade are used-Simple and Telescopic alidade. rule with two vertical vanes at the ends. horse hair. Both the slits, thus provide a definite line of sight which can be made to pass through the object.
What are alidade spirit levels?
While the plane alidade only took horizontal sights, this telescopic alidade is used to take inclined sights. It is used to increase the accuracy of the sight taken. A small spirit level tube is provided with the telescope so that the alidade can be leveled with the working station.
What is a groma made of?
use in ancient Egypt originated the use of the groma, a device used to establish right angles, but Roman surveyors made it a standard tool. It was made of a horizontal wooden cross pivoted at the middle and supported from above.
What is a dioptra used for?
The dioptra is the original survey instrument developed by Greek Astronomers for use in measuring angles.
What are the advantages of plane tabling?
Advantages of Plane Table Surveying
- The observations and plotting are done simultaneously, hence there is no risk of omitting necessary details.
- The errors and mistakes in plotting can be checked by drawing check lines.
- Irregular objects can be plotted accurately as the lay of land is in view.
What is the principle of plane table?
parallelism
The principle of plane tabling is parallelism means “All the rays drawn through various details should pass through the survey station”. Introduction: Plane table surveying is a graphical method of survey in which the field observations and plotting are done simultaneously.
What is telescopic alidade?
[¦tel·ə¦skäp·ik ′al·ə‚dād] (engineering) An alidade used with a plane table, consisting of a telescope mounted on a straightedge ruler, fitted with a level bubble, scale, and vernier to measure angles, and calibrated to measure distances.
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