Application

The Theory and History of Gyro-theodolite

In surveying, a gyro-theodolite (also: surveying gyro) is an instrument composed of a gyroscope mounted to a theodolite. It is used to determine the orientation of true north.  It uses the physical characteristics of the gyroscope itself (fixed axis and precession), the sensitive part of the gyroscope with the center of gravity moved down is used to sensitive the horizontal component of the earth's rotation angular velocity, and under the action of gravity, a northward precession moment is generated, so that the gyroscope spindle swings around the Earth's meridian plane, so as to determine the true north azimuth.It is the main instrument for orientation in mine surveying and in tunnel engineering, where astronomical star sights are not visible and GPS does not work.

History of gyro theodolite

The gyro theodolite is composed of two parts: gyroscope and theodolite. Theodolite was invented by the British in 1730, after a long process of metal theodolite, developed into an optical theodolite in the 1920s, and entered the electronic theodolite stage since the 1960s, and is now quite advanced and developing in the direction of intelligence. Gyro is the main body of gyro theodolite, which leads the development process of the whole machine.

In 1852, the French physicist Léon Foucault discovered that a gyro with two degrees of freedom points north. This principle was adapted by Max Schuler in 1921 to build the first surveying gyro. In 1949, the gyro-theodolite – at that time called a "meridian pointer" or "meridian indicator”– was first used by the Clausthal Mining Academy underground. Several years later it was improved with the addition of autocollimation telescopes. In 1960, the Fennel Kassel company produced the first of the KT1 series of gyro-theodolites. Fennel Kassel and others later produced gyro attachments that can be mounted on normal theodolites.

The gyrotheodolite can be divided into engineering class (orientation accuracy beyond 10 ") and precision class (orientation accuracy within 10 ") according to orientation accuracy. The ER-GT-02 orientation accuracy ≤3.6 "belongs to the precision level, the use of integrated fuselage design (built-in battery) not only has low locking, automatic zero observation, automatic north finding, automatic limit position, wide temperature compensation and other functions, but also has strong anti-interference ability, high stability. In addition to the speed type once used by the United Kingdom and the United States, the orientation principle is generally used pendulum. The gyroscope and theodolite are used as a whole, and there are two types of combination methods: underhanging and overhead.

Mode of use

The use of gyro theodolite is related to its structural characteristics. Generally, manual measurement method is used for overhead instruments, and automatic measurement method is used for underhung instruments. Automatic measuring instrument mainly adopts automatic tracking method, multi-point photoelectric timing method and photoelectric integration method. Among them, photoelectric integration method is the most advanced. The manual measurement method mainly adopts tracking reversal point method, transit time method, timing swing method and multi-point timing method.

Application

Tunnelling

In tunnels and other excavation projects, the measurement of the center line in the pit generally adopts a long distance wire which is difficult to guarantee the accuracy, especially in the case of shield excavation. Starting from the short reference center line of the pit, there must be a high accuracy of Angle measurement and station shifting. In the measurement, the corresponding inspection of the ground and underground should be often carried out to ensure the measurement accuracy. Especially in dense urban areas, inspection conditions are difficult and it is impossible to carry out excessive inspection operations. If the gyrotheodolite can be used to obtain an absolutely high precision bearing datum, and can reduce the cost of very high detection operations (minimum checkpoints), it is a very efficient centerline measurement method.

For more information, please feel free to contact info@ericcointernational.com

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