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This reduces the need to set the instrument base truly level, as with a dumpy level. Self-levelling instruments are the preferred instrument on building sites, construction, and during surveying due to ease of use and rapid setup time. A digital electronic level is also set level on a tripod and reads a bar-coded staff using electronic laser ...
The level must be horizontal to get a valid measurement. Because of this, if the horizontal crosshair of the instrument is lower than the base of the rod, the surveyor will not be able to sight the rod and get a reading. The rod can usually be raised up to 25 feet high, allowing the level to be set much higher than the base of the rod.
A tubular spirit level A bull's eye spirit level mounted in a camera tripod. A spirit level, bubble level, or simply a level, is an instrument designed to indicate whether a surface is horizontal (level) or vertical . Two basic designs exist: tubular (or linear) and bull's eye (or circular).
Bring the level parallel to any two of the foot screws, by rotating the upper part of the instrument. The bubble is brought to the centre of the level tube by rotating both the foot screws either inward or outward. Rotate the upper part of the instrument through 180°, so the level is over the remaining foot screw.
A level staff, also called levelling rod, is a graduated wooden or aluminium rod, used with a levelling instrument to determine the difference in height between points or heights of points above a vertical datum. When used for stadiametric rangefinding, the level staff is called a stadia rod.
The first instrument to combine the essential features of the modern theodolite was built in 1725 by Jonathan Sisson. [14] This instrument had an altazimuth mount with a sighting telescope. The base plate had spirit levels, compass and adjusting screws. The circles were read with a vernier scale.
An Abney level and clinometer is an instrument used in surveying which consists of a fixed sighting tube, a movable spirit level that is connected to a pointing arm, and a protractor scale. An internal mirror allows the user to see the bubble in the level while sighting a distant target.
Another name for a bull's eye level is a "circular bubble" which is the name used by surveyors in the United Kingdom. Surveying instruments such as theodolites (transits) and total stations often have a circular bubble as well as a tubular level or "plate level". The circular bubble is used to roughly level the instrument in two dimensions.