What is the difference between a sextant and a theodolite?
A sextant measures angles on one sixth of a circle. In general, a simple navigator’s sextant can measure with limited accuracy of about one-fifth of a degree. A theodolite is a more sophisticated instrument that will simultaneously measure both a horizontal and a vertical angle through a full 360°.
How accurate is a theodolite?
A number of investigators reported results of similar tests using theodolites, not levels. For distances less than 150 m, almost all investigators reported accuracy values in the range from 1/600 to 1/2100.
What is a theodolite used for?
theodolite, basic surveying instrument of unknown origin but going back to the 16th-century English mathematician Leonard Digges; it is used to measure horizontal and vertical angles. In its modern form it consists of a telescope mounted to swivel both horizontally and vertically.
Why is it called a theodolite?
The portable surveying instrument that we call a theodolite was invented in the middle of the sixteenth century by Leonard Digges of Kent, who gave it a name that was expressed in the common Latinate form of the time: theodelitus. The suspicion is that he was a better surveyor and inventor than he was a scholar.
What is a digital theodolite?
Digital theodolites consist of a telescope that is mounted on a base, as well as an electronic readout screen that is used to display horizontal and vertical angles. Digital theodolites are convenient because the digital readouts take the place of traditional graduated circles and this creates more accurate readings.
Do surveyors still use theodolites?
The theodolite is an instrument that can measure both horizontal and vertical angles, which allows surveyors to “triangulate” the position of objects in a specific area. While the digital and transit theodolite have been used by land surveyors and engineers, they can be used for other purposes as well.
How do surveyors use theodolites?
A theodolite works by combining optical plummets (or plumb bobs), a spirit (bubble level), and graduated circles to find vertical and horizontal angles in surveying. An optical plummet ensures the theodolite is placed as close to exactly vertical above the survey point.
Who uses theodolite?
Which theodolite are commonly used?
Vernier type theodolites are commonly used . A theodolite is designated by diameter of the graduated circle on the lower plate. The common sizes are 8cm to 12 cm while 14 cm to 25 cm instrument are used for triangulation work.
What is modern theodolite?
A modern theodolite consists of a movable telescope mounted within two perpendicular axes the horizontal or trunnion axis, and the vertical axis. When the telescope is pointed at a target object, the angle of each of these axes can be measured with great precision.
What is digital theodolite?
What do you need to know about the theodolite?
Measure the height between the ground and the instrument. This will be used a reference to other stations. Level the theodolite by adjusting the tripod legs and using the bulls-eye level. You can make slight tunings with the leveling knobs to get it just right. Adjust the small sight (the vertical plummet)…
How are theodolites used to measure horizontal angles?
Record the horizontal and vertical angles using the viewing scope found on the theodolite’s side. A theodolite is a precision instrument used for measuring angles both horizontally and vertically. Theodolites can rotate along their horizontal axis as well as their vertical axis. Theodolites have a lot in common with transits.
How does an optical plummet work on a theodolite?
An optical plummet ensures the theodolite is placed as close to exactly vertical above the survey point. The internal spirit level makes sure the device is level to to the horizon. The graduated circles, one vertical and one horizontal, allow the user to actually survey for angles.
Is there a horizontal axis error in a theodolite?
Horizontal axis error. The horizontal and vertical axes of a theodolite must be perpendicular; if not then a horizontal axis error exists. This can be tested by aligning the tubular spirit bubble parallel to a line between two footscrews and setting the bubble central.