Cross-staff
Ballestilla (báculo de Jacob náutico)
- Date
- c. 1470-1520 (uso náutico) · confidence medium
- Place
- Lisbon, Portugal, and Nuremberg
- Credited to
- Adaptation of Levi ben Gerson's staff (1342) by Portuguese navigators; Werner (1514)
- People
- 👤 Johannes Werner1468–1522
- Field
- Movement
What it is
A graduated staff with a sliding crosspiece, used to measure the altitude of the Sun or the Pole Star above the horizon in order to find latitude. A cheap, robust instrument that replaced the astrolabe on deck.
What it led to
- Astronomical navigation within reach of every pilot
- The determination of latitude on the Portuguese and Dutch routes
- Topography and field surveying
Built on
- Kamal (star altitude board)c. 1000 (uso posterior atestiguado)
- Mariner's quadrant (plumb-bob quarter circle)c. 1460
- Mariner's astrolabec. 1480-1500
- Astronomical Jacob's staff
- Solar declination tables