Spinning theodolite

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Wild GAK as an attachment to Wild T16
Horizontally tied rotor as a prototype of a surveying top. Instead of the hook, the suspension on a torsion thread could be thought of.

A gyro theodolite or surveying gyro is a special geodetic measuring and gyro instrument that is used to determine precise direction underground.

In the case of the gyro theodolite, a gyroscope instrument is / is integrated into the theodolite to determine the absolute direction . This top and its suspension are under the alidade of the theodolite. The surveying gyro is an additional gyroscopic instrument that is placed on the frame of the theodolite. Surveying gyros are no longer in use.

construction

The gyro mounted in the substructure - which, like all gyroscopes, is a sensitive, fine-mechanical device - has a smaller ground clearance than the other measuring units, which helps to reduce mechanical disturbances (shocks, vibrations, etc.). Due to this construction, most of the gyroscopic theodolites have a compact shape and require special tripods with a large tripod plate in whose hole the gyro cylinder hangs.

A very rapidly rotating, cylindrical gyro with a horizontal axis, which is suspended from a torsion band, serves as the measuring sensor . Such a horizontally tied top has the property of looking north and becomes a torsional pendulum : the rotation axis of the body of revolution is slowly pivoted ( precession ) due to the earth's rotation and tries to position itself parallel to the earth's axis - as with the gyrocompass . Under the effect of the torsion band, this precession changes into a torsional oscillation , which takes place as a damped oscillation around the true north direction.

Measurement method and accuracy

This oscillation process, the period of which is in the range of ten minutes, is analyzed with special additional equipment and the instrument is gradually turned in the exact north direction. With earlier instruments (e.g. the GK series from Wild ) this tracking was done manually by the observer analyzing the gyro oscillation either using its reversal points or using the transit method, or evaluating it in rapid approximation or graphically. Newer, semi-automated devices rotate the gyro frame using fine electronic setting circles .

Due to the gyro- theoretical connection to the earth's rotation, gyro-theodolites deliver astronomical azimuths , just like the methods of astrogeodesy , but are somewhat less precise. The accuracy of the direction measurement is (depending on the complexity of the series of measurements ) about 1 to 3 mgon (3 to 10 arc seconds ). By centrifugal azimuths in underground can traverses a direction similar stabilizing effect as solar or Laplace azimuths in above ground measurement networks can be achieved. With the Gyromat developed for the Ruhr mining industry , an accuracy of a few milligons is achieved after a short time , which can be increased with longer, extended series of measurements.

In principle, the accuracy could be even greater, but the market for such instruments is relatively small, with other developments of the underground - Measurement and unearthly GPS has to do networks. The technology that z. B. is realized in the automatic Gyromat or in light measuring platforms for inertial navigation , a measurement accuracy of just under 1 "would enable.

application

Gyroscopic theodolites are used in tunneling and mining to determine the direction of penetration . Before the introduction of satellite positioning, simpler gyroscopic instruments were used in the military sector to determine the direction of artillery and rocket units, as well as for military topographers, as they were the only way to provide exact directional information without a fixed position field .

Manufacturer

Manufacturers of gyroscopic theodolites are or were u. a. the companies Askania (Berlin), Wild (Heerbrugg), MOM (Budapest) and Deutsche Montan Technologie .

  • Wild spinning theodolite of the Finnish artillery

  • Used by the French artillery

  • Used by the French artillery

Web links

Individual evidence

  1. ↑ Exact measurements in the Gotthard Base Tunnel. Retrieved April 27, 2013 .
  2. ^ Spinning theodolite Gi-E1. Retrieved April 27, 2013 .