Surveying Instrument Collection
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Maker |
Wild, Heerbrugg (Switzerland) |
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Model |
P30 |
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Serial Number |
187 |
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Dimensions |
Telescope Length 150mm, Height 320mm |
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Image |
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Description |
This Photo-theodolite consists basically of an ordinary theodolite which is modified by the attachment of a camera in such a way that both theodolite and camera rotate about a common vertical axis. The top half of the instrument is a standard Wild T2 one-second theodolite which rests on a solid casting housing the camera. The instrument was used for terrestrial photogrammetry. The baseplate with 3 levelling screws and circular bubble is provided with a lock which serves to fix the theodolite when placed on the plate. The instrument has a roller bearing on the bottom with clamp and slow motion screw, a solid frame for the photographic camera which can be taken off, on the frame a round case with the horizontal circle and the roller bearing for the proper theodolite with vertical circle, telescope and built-in reading microscopes. The magnification of the telescope is 28x and the optical micrometer allows the simultaneous reading of opposite circle divisions directly to 1". The precision of the instrument is therefore sufficient for all geodetic work, including indirect distance-measuring with the subtense bar (e. g. determination of the base length). The camera is supported by two V-bearings of the frame and can be tilted in predetermined steps. Glass plates, with dimensions of 150 mm x 100 mm, are used as a base for the photographic emulsion, giving angular coverage of approximately 45° in the horizontal plane and 30° in the vertical plane. The focal distance of the distortion-free lens is 165 mm. Lens and pressure frame for the negative plates are both solidly mounted on a rigid cone, which guarantees a very high stability of the calibration. The camera includes a three-digit counter, the numbers of which appear in the photograph. So, each exposure can be given a distinct reference number. |
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History & comments |
It should be noted that the pointing of the theodolite is completely independent of that of the camera, but the horizontal circle, which is located on the top of the camera housing, is fixed in such a way that when the circle reading is zero, the optical axes of the theodolite and camera lie in the same vertical plane. This means that all horizontal directions observed with the theodolite can be easily related to the principal point of the photograph. |
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Conservation |
There are four separate boxes for the theodolite and camera, and two boxes of glass plates. |
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Condition |
The camera is not operational. |
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Remarks |
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Dates |
Manufactured in 1950 (approx). Catalogued in 1997. |
