Building theodolite
As Theodolite in geodesy is a robust theodolite called, the for the most common measurement tasks in construction is designed for simple and ground surveys. It differs from the universal or second theodolite in that it is somewhat smaller in size and accuracy (approx. ± 3–10 ″ or 1–3 mgon ). The term came up around 1950, when the closed, compact design of theodolites had become generally accepted.
The Wild T1 and Kern DK1 devices designed by Heinrich Wild around 1930 can be counted among the first theodolites of this type, soon followed by comparable measuring devices from Zeiss (e.g. Th2), Neuhöfer and other manufacturers.
The classic (analog) building theodolite weighs around 5 kg and has dimensions of around 10 cm × 10 cm × 20 cm. The tripod used can therefore be light (4–5 kg). In older specimens, the pitch circles are usually only divided to degrees or 10 ′; the reading is made with a scale microscope (arc minute or cGon direct, second or milligon estimated). All simple measuring tasks can be solved with accessories such as measuring rods , small spacers , lighting, etc.
Since the 1990s and the digitization of measurements, the design has merged with the instrument type of the total station .
For robust construction
Until about 1900 the open construction of the theodolites prevailed; that is, the tilt axis , the partial circles and the various Ablesenonia were exposed. This meant relatively great sensitivity of the instruments and required experienced observers.
At the turn of the century, the development of the closed construction began: the alidade with the horizontal circle was vaulted with a metal shell, the telescope supports were clad, and from around 1930 also the height circle and the tilt axis. The next development step - which goes back above all to Heinrich Wild - was the simplification of the circle reading with small telescopes and by mirroring opposing partial circles, as well as the replacement of metal circles with glass ones .
The closed device case brought some advantages:
- Robustness and thus usability even with less experience
- Reduction of the thermal influences on alidade, telescope axes and reading
- Better protection of dragonflies
- adjustable, but dust-protected tilting axis and more stable rectification