record number: | 11 |
instrument type: | theodolite |
manufacturer: | Ertel & Sohn München |
serial number: | 32156 |
weight: | 8.99 kg |
dimensions (l/w/h): | 37/28/41 cm |
year of manufacture: | 1900 |
centering and leveling the instrument: |
plumb bob
two perpendicular toric levels on the alidade centrally set circular level vertical circle level, tilting screw precise reversible level on telescope striding level adjustable to telescope supporting column |
The tacheometer-theodolite is one of the most sophisticated theodolites of its time. It was made at the beginning of the 20th century. It stands out for its complexity and precision in measuring horizontal directions. Worthy of mention are the number and types of levels: a circular level, two horizontal circle (alidade) toric levels, a reversible levelling toric level, a striding level and a vertical circle level. The horizontal circle with a diameter of 18 cm and the reading of the division at two diametral points with a screw microscope (German: Schraubenmikroskop) with a micrometer screw provide an incredible resolution of mechanical determination of the reading, i.e., 1''.
The theodolite was still used in the 1960s for measurements in trigonometric nets of lower orders. In 2016, the instrument was completely restored and lacquered, and a new frame for the diaphragm and mirror for the striding level were made.
horizontal circle | vertical circle | |
---|---|---|
diameter: | protected, closed, 18 cm | protected, 15 cm |
type of division: | engraved division | engraved division |
limb implementation: | silvered metal bracket | silvered metal bracket |
division: | sexagesimal/sexadecimal | sexagesimal/sexadecimal |
unit: | 10' | 10' |
Reading | ||
number of reading points: | 2 | 2 |
reading device: | screw microscope | vernier |
number of units: | division of the graduation unit into 5 parts, a fifth is 120 units | 60 |
graduation unit: | 1'' | 10'' |
repetition: | clamping and micrometer screw | / |
Telescope | ||
diameter of objective: | 30 mm | |
magnification: | 17 x | |
type: | telescope with internal focusing | |
cross hairs/reticule: | Reichenbach's crosshairs, constant 100 |