Improvements and Spread of Navigation Instruments (1501–1510)

Timeline

1. 1501–1506Lisbon · PortugalA royal Portuguese center for navigational information and instrument making concentrated in Lisbon, where astrolabe and compass production became increasingly standardized, and ship's logs systematically recorded solar and Polaris altitude observations, improving latitude reckoning.
2. 1505–1510Seville · AndalusiaThe cross-staff gradually replaced some astrolabe functions aboard Iberian and Italian merchant ships, facilitating celestial altitude measurement on a rolling deck; meanwhile chartmaking combined Portuguese route data with Mediterranean port information, with navigation instruments and cartography mutually reinforcing each other.