What information do you need to determine your longitude?

Answer 1

The information you need is the degree's the earth has turned in so many hours and the time in your area

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You pick a star and measure its hour angle. You convert that to local mean time, and compare with a clock of known accuracy. The difference can then be translated into longitude. Note: It is best to pick a star near the celestial equator, so as to minimize error. The same thing can be done during the day - you just pick the Sun as your star.

Answer 2

You can calculate it if you know the position of a star in the sky as seen from a

known longitude RIGHT NOW, and you measure the position of the same star in

your sky RIGHT NOW, and then go inside and do some spherical trigonometry.

Alternatively, you could find a US Geodetic Survey surveyor's benchmark near you,

look up its longitude, measure off your position relative to that marker, and then

do more spherical trigonometry.

But it's a lot easier just to look up your longitude on a good map, or read it from

a good GPS receiver.

Answer 3

To determine your longitude, you need the current time at your location and the time at a reference point such as Greenwich, England. The time difference between the two locations allows you to calculate your position east or west of the reference point, given that the Earth rotates 360 degrees in 24 hours.

Answer 4

Latitude and longitude are normally helpful.