Using a Cross Staff

A mariner could use a cross staff to measure the Sun’s angle above the horizon at midday. From Jonas Moore, A New Systeme of the Mathematicks, 1681.

Caption:
A mariner could use a cross staff to measure the Sun’s angle above the horizon at midday.
Type: Illustration
Credit: Smithonian Institution Libraries
Origin: Smithsonian Institution
Navigation Methods
 
A mariner could use a cross staff to measure the Sun’s angle above the horizon at midday.