Hobbies And Interests
Cross Staff and Back Staff
The cross staff and back staff are simple measuring devices with notches and sliding markers to measure the angle of the sun or the North Star over the horizon. The cross staff is the simpler of the two, however, it can be difficult to use during the day, as it requires the user to look directly into the sun, which can cause severe eye damage. The back staff uses shadows cast by the sun, so users have their back to the light. The primary drawbacks of these devices are that they are impossible to use on overcast days and are not as accurate as other tools.
Quadrants and Sextants
Quadrants are more sophisticated versions of the cross and back staffs. Sextants are more accurate versions of quadrants. They also measure the angle between two bodies, which can include the horizon and the sun, the North Star, or the angle between two stars. Quadrants have small sights in which you locate your navigational star, a fixed scale, and a string that hangs down and marks the spot on the scale. To use a sextant, a navigator looks through the eyepiece and adjusts a movable arm with mirrors until the celestial body appears to be in line with the horizon, and the angle is read off a fixed scale that is attached. Sextants can be highly accurate, calculating angles with great precision. Quadrants, while easy to operate, require the user to stand perfectly still in order to get an accurate reading.
Global Positioning Systems (GPS)
GPS is a satellite based communications system that can give users near instant readings (depending on signal strength) of their latitude, longitude and altitude. GPS is used to navigate in the air, on land and on water, and provides a high degree of accuracy. Your GPS receiver sends a signal to the satellite, which transmits your latitude information back. Additionally, the receivers can calculate directions and distance between two points, as well as exact location. Many online mapping services use GPS data in order to calculate latitude.