Tavernier-Gravet Proportional sector
Tavernier-Gravet proportional sector
Obtained from the Netherlands
This is a large (around 42 cm) sector. Like the Gunter sector, this was used for computing scales and angles and could have been used in drawing. The Netherlands Hydrographic Office used such a sector for plotting their readings (Snellius measurements) rather than the station pointer according to 'Hydrografisch Opnemen' published in 1938 and 1952. In daily practice it was called 'tang' translated as 'pliers'. This one has scales on the front and the back of the instrument.
8 other products in the same category:
Tavernier-Gravet proportional sector
Obtained from the Netherlands