Here's my guess, but i suspect I'm about to learn something:
Woods is a more difficult problem vs water, since you probably don't have a
good horizon. You could probably rig a poor-man's sextant using a plumb line
(shoestrings?) to get a decent vertical and fake a perpendicular line to
that as a horizon line. Then at night take a sight on Polaris, use a
wristwatch as a makeshift protractor (6 degrees/min) and get your lattitude.
Should be good within 5 degrees or so if you're careful. But 5 degrees is
about 300NM so its not a huge help.
> A question for Nav 201 levels:
> All you have is a clock/watch. You don't know where you
> are. How many hours away from Greenwich are you?
> You don't know what your watch is set to. You can
> use any pre-1800 tools available to navigators, but no
> maps or charts. There's no-one around to ask questions
> of, either.
If you happen to know the lat/long of magnetic north, and have a compass,
you >might< be able to narrow it down out via variance between the magnetic
reading and a polaris sighting in the northern hemisphere. But I don't think
it will get you close enough, and areas with the same variance can span
multiple time zones.
Since greenwich is an arbitrary location, there's no way to do this without
celestial tables. This would work: Assume the watch keeps decent time, and
we're in the northern hemisphere. But the actual time it is set for is
unknown...but an hour on the watch is a true hour. At night, get a polaris
direction. Use this to draw the NORTH line on a sundial, and also to
determine lattitude. At noon the next day, the shadow will point due north
at local noon (or close enough). Set the watch. You now know the time close
enough for this experiment. Navigators pre-1800 still had celestial tables,
no? Presume we have an accurate sextant, or have built a workable makeshift
one. At a specific local time, assume you are at the same longitude as
greenwich. Using the celestial tables backwards, check to see if the stars
(moon wouldn't work well for this example cuz its position changes way too
fast) are where they should be at this time in greenwich. If they are,
you're in the same time zone. If they are not, find an entry which puts you
an 15 degrees (1 hour) ahead of greenwich, and check for fit with the stars
again. lather rinse repeat, or do it backwards if you have to. Eventually
you will find a close enough fit. It should get you within an hour anyways.
There's probably a better way than that. I'd love to hear them. I don't have
any practical experience with celestial navigation - I only know the theory
behind it. This would be a time consuming method because the tables
presumably have their output in longitude, so you'd have to find a cell in
the table with the assumed longitude and work back to find the time and the
correct stars.
Am I close?