Measuring table
A measuring table is a (historical) tool used by the geodesist or topographer when surveying the terrain for the production of cadastral or site plans using the graphic / drawing method. It is made of wood with exactly planar and distortion-free surface and can be set via dragonfly level up . The size is typically 40 cm × 40 cm - 60 cm × 60 cm.
Johannes Praetorius (1537-1616) is considered to be the inventor of the measuring table, the so-called Mensel (Mensula Praetoriana), which is attested by his student Daniel Schwenter .
For the purpose of angle measurement, the measuring table was screwed onto a three-legged measuring stand, which was set up centrally over a measuring point . The recording sheet , a drawing sheet or a map to be updated (also called mapping ) was attached to the wooden plate . The orientation of the measuring table was made depending on the purpose of the recording to the north, south or a preferred direction in the landscape (e.g. valley course). For orientation to geographic north, see orientation (map) .
The point (usually a measuring point) over which the measuring table was set up was transferred to the recording sheet (usually with a mapping needle ) with a plumb line fork or another suitable aid by means of a puncture, the “ pricking ”, on the recording sheet .
The most important tools on the measuring table were:
- A plumb fork to position the map with a marked reference point above the plumb point of the table
- The freely movable tilt rule or a diopter ruler - exactly on the measuring point marked with the mapping needle - to measure and draw directions to detailed points in the terrain
- A Bussole (precision bearing compass )
- General drawing equipment, such as pencil , eraser , drawing triangles, rules, rulers, stencils, conveyor etc.
- Mapping needle
After completing the measurements, the mapping with the recorded detail and boundary points was drawn in the office. The measuring table also gives its name to the measuring table sheet . For small operations , instead of surveying points, initially unknown locations were used, the mutual position of which was determined by graphic triangulation .
Similar instruments are still occasionally used for simple measurements. The graphical method has the advantage of doing without calculations in the small area.
Individual evidence
- ↑ Ralf Kern: Scientific instruments in their time. Volume 1: From astrolabe to mathematical cutlery. 15th and 16th centuries. König, Cologne 2010, ISBN 978-3-86560-865-9 , p. 383.
