backstaff造句

• This form of the instrument became synonymous with the backstaff.
• It was one of the most widely used forms of the backstaff.
• George Adams Sr . created a very similar backstaff at the same time.
• Ultimately, the cross-staff could not compete with the backstaff in many countries.
• In terms of handling, the backstaff was found to be more easy to use.
• Perhaps influenced by the backstaff, some navigators modified the cross-staff to operate more like the former.
• As a navigational tool, this instrument was eventually replaced, first by the backstaff or octant and the sextant.
• However, it has been proven by several authors that in terms of accuracy, the cross-staff was superior to the backstaff.
• For these higher-latitude needs somewhat more complex devices based on the same principle were used, notably the cross-staff and backstaff.
• The Backstaff, which measures the length of a shadow, was used from the 16th century and saw iterative improvements such as the Davis quadrant.
• Seventeenth century marine navigation and cartography used the " backstaff " which, in this area, was accurate to one degree of longitude, or around 60 nautical miles.
• However, as engraved, they showed the instrument to have an apparent accuracy of only two minutes of arc while the backstaff appeared to be accurate to one minute.
• Navigators had been able to work out latitude accurately for centuries by measuring the angle of the sun or a star above the horizon with an instrument such as a backstaff or degrees relative to the sun each day.