Development of Surveying Instruments Flashcards
is considered to be one of the best known of the measuring instruments that have come down from ancient times. It was developed sometime in 140 B.C., and further improved by Ptolemy.
Astrolabe
Invented in 1607, the _________ is used for astronomical observations.
Telescope
Invented by Young and Draper back in 1830, it is also known as the universal surveying instrument.
Transit
An early surveying instrument which was used to measure and layoff angles, and establish lines of sight by employing peep sights.
Semicircumferentor
One of the oldest types of surveying instruments used in field mapping. It consists of a board attached to a tripod in such a way that it can be leveled or rotated to any desired direction.
Plane Table
Used in leveling and for measuring horizontal and vertical angles. It consists es-sentially of a copper tube supported on a standard and could be rotated in either a horizontal or vertical plane. For measuring horizontal angles, a flat circular disc with graduations in degrees is used. An arm containing sighting apertures at either end could be rotated to any desired position on the disc.
Dioptra
Instrument for aligning· or sighting as an points. It consisted basically of cross arms fixed at right angles and pivoted eccentrically upon a vertical staff. Plumb lines were suspended from the ends of the arms. By employing the groma two lines at right angles to each other could be established on the ground where it is set up.
Roman Groma
The instrument had an a frame with a plumb line suspended from its apex and was used to determine the horizontal. Archeologists are of the belief that the horizontal foundations of the great pyramids of Egypt were probably defined by this device.
Libella
Is a short auxiliary scale placed alongside the graduated scale of an instrument, by means of which fractional parts of the smallest or least division of the main scale can be determined precisely without having to interpolate. It was invented in 1631 by a Frenchman name Pierre Vernier.
Vernier
An instrument developed by the Greeks sometime in 130 B.C., and known to be their most famous surveying instrument. The __________ was used for leveling, laying off right angles, and for measuring horizontal and vertical angles. Since the telescope was not yet invented during the time the __________ was used, peep sights were employed for sighting and in aligning the device.
Diopter
Used for determining the direction of lines and in calculating angles between lines. It was first introduced for use in navigation. The _____________ consists of a magnetized steel needle mounted on a pivot at the center of a graduated circle. The needle continues to point toward magnetic north and gives a reading which is dependent upon the position of the graduated circle.
Compass
Is invented by Sir Edmund Gunter in 1620, was the forerunner of instruments used for taping distances. It is 66 ft long and contains 100 links, so that distances may be recorded in chains and in decimal parts of the chain. Each part, called a link, is 0.66 ft or 7.92 inches long.
Gunter’s Chain
This instrument was designed for le¬veling work. It consisted of a horizontal straight-edge about 6 meters long with supporting legs, and a groove 2.5 cm deep and, 1.5m long on top. Water is poured into the groove and when the bar is leveled so that water stood evenly in the groove without spilling, a horizontal line is established.
Chorobates
was a device for measuring time and meridian. It was first used by the Chaldeans in about 4,000 B.C. It consisted of a slotted palm leaf through which to sight and a bracket from which a plumb bob was suspended. -By sighting through the ‘slot and past the plumb bob string, a straight line could be projected.
Merchet
the process of determining the extent, size or dimensions of a particular quantity in comparison to a given standard.
Measurement
