Surveying Instrument Collection
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Maker |
Wild, Heerbrugg (Switzerland) |
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Model |
T0 |
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Serial Number |
48552 |
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Dimensions |
Telescope length 135 mm, Height 220 mm |
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Image |
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Description |
This Wild T0 compass theodolite is a compact lightweight instrument, which can be used either for observing and setting-out magnetic bearings or as a normal theodolite for measuring or turning-off angles. It is particularly useful for rapid traversing, based on magnetic bearings, especially in areas where visibility is limited and the traverse legs likely to be short. The T0 can also be used for photogrammetric ground control surveys, low-order detailing, on building sites or as a reconnaissance instrument. The freely-swinging compass circle is oriented to magnetic north by means of its rigid attachment to a north-seeking needle, which rests on a pivot at the centre of the instrument. The theodolite has a lever which has to be moved to lower the compass circle on to its pivot. The horizontal (compass) circle consists of a metal circle with a diameter of 68 mm. The method of reading the horizontal circle, which is graduated and numbered in 2° intervals, is the same as with the Wild T2. Using the micrometer, readings of the horizontal circle are made directly to 1' and estimated to 30". Horizontal circle readings are of unusually high accuracy for an instrument of this type and size, because of the coincidence setting of the diametrically-opposite parts of the circle. The vertical circle is made of glass and has a diameter of 46 mm. Once the vertical circle index bubble (altitude bubble) has been centred, the reading of the vertical circle is obtained as the mean of the combined images of the diametrically-opposite parts of the circle, but without a micrometer setting. Therefore, the readings are made directly from the circle to 10' and estimated to 1'. As a slight inconvenience, however, the horizontal and vertical circles are read separately from two different reading microscopes. The vertical circle is read through the reading microscope situated next to the telescope eyepiece, while the horizontal circle is read through a separate reading microscope located on the left side of the instrument (in FL). The telescope produces an inverted image. The magnification of the telescope is 20x, the diameter of the objective lens of the telescope is 28 mm and the shortest pointing distance is approximately 1.4 m. The sensitivity of the vertical circle index bubble per 2 mm is 1'. |
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History & comments |
There is no historical information available. |
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Conservation |
Metal container |
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Condition |
Not operational since instrument has been dropped. |
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Remarks |
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Dates |
Manufactured in 1956. Catalogued in 2000 & 2005. |
