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After the instrument is centered within a few cm over the mark, the plumb bob is removed and a viewer (using a prism) in the instrument is used to exactly center it. The top is typically threaded with a 5/8" x 11 tpi screw thread. The mounting screw is held to the underside of the tripod head by a movable arm.
It is also known as a surveyor's level, builder's level, dumpy level or the historic "Y" level. It operates on the principle of establishing a visual level relationship between two or more points, for which an inbuilt optical telescope and a highly accurate bubble level are used to achieve the necessary accuracy. Traditionally the instrument ...
The pibal theodolite uses a prism to bend the optical path by 90 degrees so the operator's eye position does not change as the elevation is changed through a complete 180 degrees. The theodolite is typically mounted on a rugged steel stand, set up so it is level and pointed north, with the altitude and azimuth scales reading zero degrees.
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American soldiers using a coincidence rangefinder with its distinctive single eyepiece during army maneuvers in the 1940s. A coincidence rangefinder or coincidence telemeter is a type of rangefinder that uses the principle of triangulation and an optical device to allow an operator to determine the distance to a visible object.
Davis quadrant, made in 1765 by Johannes Van Keulen. On display at the Musée national de la Marine in Paris. Captain John Davis invented a version of the backstaff in 1594. Davis was a navigator who was quite familiar with the instruments of the day such as the mariner's astrolabe, the quadrant and the cross-staff.
With January rapidly approaching, nearly half of our top 50 free agents have agreed to new contracts, ranging in magnitude from Juan Soto’s $765 million mega-deal with the Mets to Danny Jansen ...
The Specter was developed by Raytheon Six Sigma Product Development Team under Raytheon ELCAN Optical Technologies for the United States Naval Surface Warfare Center to fill the requirement for the "SOPMOD rifle kit SU-230/PVS Articulated Telescope NSN 1240-01-533-09039", development was started in 2003 with the goal to fix the general issue of transition between long-range engagements ...