Diopter
The dioptra is a universal geodetic instrument that can be regarded as the early predecessor of the theodolite . The invention of the theodolite in the sixteenth century was inspired by the description of the dioptra in Heron of Alexandria .
A dioptra consists of a vertical cylinder which axially supports a rotatable disc that is labeled with a graduation . A horizontal rail ( alidade ) is rotatably mounted on this disc, which is provided with attachments at both ends into which viewing slots are inserted (the " diopter "). With the help of these slots, a target can be aimed precisely.
On its underside, the disc is connected to a semicircular, toothed and also graduated plate. This entire upper part of the dioptra described so far rests in turn on a disc that can be rotated and adjusted by spindles. Heron of Alexandria also mentions a canal balance in connection with the dioptra - a two-meter-long horizontal rod that carries two connected water containers.
Both horizontal and vertical angles can be measured and determined with this device.
There is a relationship to the bearing disc .
The dioptra can be used for a wide variety of field measurement and astronomy tasks.
The dioptra is described for the first time in Heron of Alexandria . When this lived can only be determined very imprecisely, most likely in the 1st century AD. However, the dioptra was invented much earlier: The Almagest mentions a (not preserved) description by Hipparchus .
Other ancient surveying instruments
literature
- Hero Alexandrinus: Heronis Alexandrini opera quae supersunt omnia. Vol. III: Rationes dimetiendi et commentatio dioptrica. Greek and German by Hermann Schöne . BG Teubner, Leipzig 1903, pp. 189ff. (Bibliotheca scriptorum Graecorum et Romanorum Teubneriana) , digitized - Internet Archive .
- MJT Lewis: Surveying Instruments of Greece and Rome. Cambridge University Press, Cambridge u. a. 2001, ISBN 0-521-79297-5 .