© Duane A. Cline 1999
Click here to return to the Main Page of The Pilgrims & Plymouth Colony:1620
Navigation: The Cross Staff The cross-staff consisted of a long staff with a perpendicular vane which slides back and forth upon it. The staff is marked
with graduated measurements -- calculated by trigonometry. The angles can then be measured by holding it so the ends of
the vane are level with the points to be measured. Early in the sixteenth century it was already in use as a seaman's navigational instrument. It was introduced into England in the mid-sixteenth century, where it was further developed to measure the angles between
stars, and to measure the heights of buildings or topographical features such as mountains and hills. Originally the staff had only one vane and was very long. Therefore, it was very difficult to manage on a rocking ship. The
mariners added more vanes in order to reduce the length of the staff to about 2 1/2 feet. The long, medium and short vanes
on the staff were about 15, 10 and 6 inches in length. The staff was then calibrated directly into degrees for use on board a
ship. For the most part, the cross-staff was used to find the latitude by measuring the altitude of the Pole Star above the horizon.
This, of course, was useless in cloudy weather. It could also be used to determine the altitude of the sun, but this required the observer to look directly into the blinding sun.
In the early seventeenth century, the back-staff was developed to avoid this problem. It would not be practical to make a cross-staff because of its length and detail. However, the teacher might want to include
the worksheet as a coloring page to be added to the pupils' notebooks.
Last modified October 7, 1999
by
Webmaster Dave Lossos