Lost at Sea
Using a Sextant
With the Captain’s sextant damaged beyond repair, you decide to build one.
At exactly noon you take a reading of the sun;s altitude using your sextant.
View the animation showing the use of the sextant.
Sextant readings are only useful if you also know the exact time. It is not enough to know the local time, you must know what the Greenwich Mean Time (GMT) is.
This is the time it is if your clock was set to the local time in Greenwich, England, where the longitude equals 0o. Knowing your last position, you use the current GMT to find out what the GMT is when it is noon onboard the ship.