How do I calculate my location based only on the time of day/sunrise/sunset?

Don Black

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Dec 11, 1998
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This is kind of a brain teaser for all of you space buffs. It has something to do with the position of the sun and the time of day at two different places. That somehow allows you to determine your longitude and lattitude. Any ideas guys? =)
 

Julie K

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GPS unit.
Well, that's the best

A sextant can be used, and what was traditionally used at sea, but on land a regular surveyor's theodolite can be used. Finding your location on land is easier too since you don't have to take the ship's motion into account. It's been a long time since I did this, so I'll just refer you to Textbook on Spherical Astronomy by W.M. Smart (Hey, if I had to wade through that old textbook with antiquated calculation methods, then you should too.)
But basically, you measure the altitude of the sun or a star at two different times (or three on land for a very accurate fix). You will need an accurate time signal and knowledge of the sun's ephemeris if you use that. (You will also need to know the angular diameter of the sun at the time you make the measurements). If on a ship you need to have an approximate idea of where you are and the direction and speed you're traveling.
Really, GPS is much better.
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[Edited last by Julie K on September 06, 2001 at 10:46 AM]
 

Glenn Overholt

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You're not saying that you're supposed to look at the sun through a surveyor's instrument and go blind, are you? Just curious.
Glenn
 

BrianW

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You're not saying that you're supposed to look at the sun through a surveyor's instrument and go blind, are you?
Glenn, that’s the price one pays for knowledge. Of course, only those crew members whose eyes were considered expendable were used to survey the sun’s position. Why do you think eye patches were once so prevalent among sea-faring men?
 

Julie K

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If you have a mylar filter, designed especially for solar observations, over the front of the theodolite, then yes, you can look directly at the sun through it. If you don't have one, then you can rig something up to project the image onto a metal plate.
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Jay H

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Why do you think eye patches were once
so prevalent among sea-faring men?
Sailors trying to pick their noses in rough seas?
Angry parrots?

Actually, the method that I posted a link to tells you to use the shadow of the sun, not looking at it...
Jay
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BrianW

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Actually, the method that I posted a link to tells you to use the shadow of the sun, not looking at it...
How clever! It’s a good thing you told me this while I’ve still got one eye left! Thanks!
That reminds me. I’ve got to check the batteries in my laser pointer…
 

Jay H

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Well BrianW, the sun method via sight only works twice, apparently, you have one more attempt. The next method of determining your lat/long and part 2 of Don's question is calculating your lat/long using only a strand of cooked (al dente) spaghetti and your nose.

Jay
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