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   VERTICAL STAFF TACHEOMETER  
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  Surveying Instrument Collection 

Maker

Wild, Heerbrugg (Switzerland)

Model

RDS

Serial Number

67528

Dimensions

Telescope Length 190 mm, Height 290 mm

Image

Wild RDS Vertical Staff Tacheometer

Description

This Wild RDS Vertical Staff Tacheometer is designed for use with a vertical staff for tacheometric surveys and setting-out on construction sites. Used as a normal theodolite, the RDS corresponds to the Wild T16 (also included in collection) as a fully-fledged direct scale-reading instrument, with the normal stadia lines however, being replaced by very flat curves projected into the field of view. These flat reduction curves give a direct horizontal distance reading and a height difference involving no tables and only a simple mental multiplication. These readings are read directly as intercepts of a graduated vertical staff at one telescope pointing.

For reading, the graduation images are arranged so that gross errors are virtually eliminated. In both telescope positions the image of the vertical circle is seen at the top of the field of view and the image of the horizontal circle is seen below. The circles are divided into whole degrees, with each degree numbered and the minute divisions of the optical scale run from left to right. The smallest interval on the optical scale is one minute (1') and each tenth minute is numbered. Estimations of the optical scale can be made to 0.1 of a minute (0.1'). 

The clear objective aperture of the telescope is 40 mm and the shortest focussing distance is 2.4 metres. The diameters of the horizontal and vertical circles are 79 mm and 70 mm respectively. The bubble sensitivity of the plate level and the index level per 2 mm is 30" and the setting accuracy of the index level is 1". The bubble sensitivity of the circular level is 8 minutes (8').

 

History & comments

This instrument was developed by Wild, Heerbrugg, in about 1950. The accuracy, of both distance and height measurements, depends on how well the position of the reduction curves can be estimated within the image of a staff interval. Typically, the distance accuracy that can be expected is about 10 cm over a normal sighting range of 100 m.

Conservation

In a storage case

Condition

Good, well maintained

Remarks

  • The telescope provides an upright image with 24x magnification
  • The RDS has a detachable tribrach for forced centring and an optical plummet in the alidade (similar to the T16)
  • Weight of instrument is 7.1 kg.
  • Thanks to J. Dedual for providing the correct year of manufacture.
  • Catalogued by T. Ko
  • Updated by F. Pall & J.M. Rüeger

Dates

Manufactured in 1957. Catalogued in 1997 & 2005.

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