Davis quadrant

What it is

A solar-altitude instrument used with the observer's back to the Sun, projecting its shadow onto a graduated arc, thereby avoiding glare and improving the accuracy of the latitude fix. It was the standard instrument of the English navy for 150 years.

What it led to

• More reliable latitudes on the English and Dutch Atlantic routes
• The instrument-making culture of London's instrument-maker workshops
• The conceptual basis of the reflecting octant

Built on

• Astronomical quadrantc. 850
• Cross-staffc. 1470-1520 (uso náutico)
• Mariner's astrolabec. 1480-1500

Made possible

• Octant and sextant1731 (octante) / 1757 (sextante)
• Hadley's octant (1731)

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