الإنجليزية - الإنجليزية
تعريف cross-staff في الإنجليزية الإنجليزية القاموس.
- An early navigational instrument, consisting of a wooden rod with a sliding crosspiece, used for measuring the altitude of a star; it developed into the sextant
- An early sixteenth-century instrument for measuring the altitude of a heavenly body It consists of a square shaft and a sliding cross-piece set at right angles to the shaft The shaft end is held at the observer's eye and the cross-piece positioned to line up with the sun and the horizon The cross-piece marks a point on the shaft that is referred to in a table of degrees and minutes
- a navigation instrument for finding latitude, it was eventually replaced by the backstaff which didn't require looking at the sun to use
- A navigational aid, the most accurate device of its kind, probably invented in the east and now used widely by pilots throughout western seas The cross staff consists of a square rod, approximately three feet in length Each of the rod's four faces are engraved with a different scale of degrees Four short cross-pieces of different length are used, depending on the size of angle that is to be measured Each crosspiece is designed for one of the four scales " The observer points the rod roughly midway between the object of the sight and the horizon, and moves the cross-piece until it exactly fits between them He then reads the altitude from the appropriate scale
- crossstaff
- An instrument formerly used at sea for taking the altitudes of celestial bodies
- crossstaff
- A surveyor's instrument for measuring offsets