The term Jacob's staff is used to refer to several things, also known as cross-staff, a ballastella, a fore-staff, a ballestilla, or a balestilha. In its most basic form, a Jacob's staff is a stick or pole with length markings; most staffs are much more complicated than that, and usually contain a number of measurement and stabilization features.

The cross-staff was a navigational tool used to measure the angle between the horizon and a celestial body such as the sun or stars. By knowing this angle, a navigator could then determine his latitude and direction. The cross-staff is also referred to as the fore-staff and the Jacob’s staff.

May 2, 2014 · In China cross-staffs are described for use in surveying as early as 1086, while in the West the first description is by the astronomer Levi ben Gerson in 1342 for use in astronomy.

Dec 26, 2020 · The cross-staff (also known as the baculus or Jacob's Staff) was one of the earliest navigation instruments devised by Henry the Navigator's school of navigation. As seen in the illustration...

Cross-Staff The cross-staff is an instrument used to measure angles and altitudes, consisting of a trigonometrically graduated staff and one or more perpendicular vanes moving over it.

Apr 14, 2015 · The cross-staff had developed from the tenth-century Arab kamal. It consisted of a square staff 3.5-4 feet in length, bearing a scale, with four sliding cross-pieces or transversals of graduated lengths.

The other instrument was also called a cross-staff, or a fore-staff, or (around the Mediterranean) a balestilha. It comprised a staff with cross-pieces designed to allow the user to determine angles of distant points.

By this time one of the prin-cipal instruments for celestial navigation at sea was the cross-staff. The others were the mariner’s astrolabe (Fig. 1) and the quad-rant (Fig. 2).

Jan 20, 2023 · A cross staff, also known as a Jacob's staff or a surveyor's staff, is a measuring instrument that was historically used in land surveying and navigation. The instrument consists of a long, straight staff with a transverse bar, or crosspiece, …

5 days ago · The cross-staff comprises a square-cut wooden staff about 76 centimetres (30 in.) in length with, at right angles to the shaft, a cross-piece known as the transversal that could slide up and down the staff.