Steve Jackson Games - Site Navigation
Home General Info Follow Us Search Illuminator Store Forums What's New Other Games Ogre GURPS Munchkin Our Games: Home

Go Back   Steve Jackson Games Forums > Roleplaying > GURPS

Reply
 
Thread Tools Display Modes
Old 10-27-2018, 11:20 AM   #41
johndallman
 
Join Date: Oct 2010
Location: Cambridge, UK
Default Re: [Basic] Skill of the week: Navigation

Quote:
Originally Posted by Vaevictis Asmadi View Post
Does anyone know enough about low-tech astronomy and navigation tools to suggest which ones would still be useful on Middle-earth, when it was flat?
My impression is that stars in Middle-Earth behaved very much like those in the skies of Earth. What is not clear is if they were close in comparison to the size of Middle-Earth, in which case you could tell something about your north-south position from their height in the sky, or distant, when you could not.

The only information on that I can think of is the tale of Eärendil, which suggests that they were close, and that's consistent with the reasonably ready navigation across the oceans of Middle-Earth by the Teleri and the Númenorians.

Quote:
Out of the ones in Low Tech, it looks like maybe the mekhet (TL1) and windrose (TL2) (measuring directions of fixed stars), and sunstone (TL3+1) (measuring direction of the sun) would still work.
With close stars the windrose is not useful, because no stars are fixed. The other two work, I think.
Quote:
It isn't clear to me whether dead reckoning is possible on a flat world, or whether it makes ocean crossings feasible.
Dead reckoning is certainly possible on a flat world, and you can certainly try to cross an ocean with any navigational method, it's just a question of how far you arrive from your target on the far side.
Quote:
The Polynesian methods aren't explained other than the stick chart, and LT doesn't say whether that relies on types of currents that only exist in the Pacific.
No, it does not.
johndallman is offline   Reply With Quote
Old 10-28-2018, 09:00 AM   #42
Vaevictis Asmadi
 
Join Date: May 2007
Location: Twin Cities, Minnesota, U.S.A.
Default Re: [Basic] Skill of the week: Navigation

Thanks, that'll help a lot! :)

Quote:
Originally Posted by johndallman View Post
With close stars the windrose is not useful, because no stars are fixed.
Interesting! Although I can imagine a world (not Middle-earth) where the stars are close and attached to a solid celestial sphere that rotates. In that case maybe they would be fixed enough to use windroses.

Another thing that has occurred to me is that a magnetic compass won't work on every world. They probably would work on Middle-earth, but not necessarily on every flat world, and probably not on a terraformed Mars. That would impact both land and sea navigation, although on Mars people would have GPS or ultra-tech tools, unless they were post-apocalypse, or low-tech Martian natives. Conversely, a flat world could have multiple poles, like Exalted with its poles of Air, Water, Fire, and Wood, and magical elemental compasses.

Things might get funky with compasses on a world like Ganymede, which has a magnetic field but is also embedded in Jupiter's much stronger magnetic field. But again, ultra-tech tools would probably compensate for that.

Navigation might be especially difficult on a world like Kricket (from Hitchhiker's Guide to the Galaxy). There are no visible stars, and the natives have no GPS satellites, and no concept of even using the sun to tell directions. A similar situation might occur for planets orbitting a star that has been flung out of its galaxy cluster, into one of the great voids in the universe.
__________________
I have Confused and Clueless. Sometimes I miss sarcasm and humor, or critically fail my Savoir-Faire roll. None of it is intentional.

Published GURPS Settings
(as of 4/2013 -- I hope to update it someday...)

Last edited by Vaevictis Asmadi; 10-28-2018 at 09:42 AM.
Vaevictis Asmadi is offline   Reply With Quote
Old 10-28-2018, 10:27 AM   #43
Daigoro
 
Daigoro's Avatar
 
Join Date: Dec 2006
Location: Meifumado
Default Re: [Basic] Skill of the week: Navigation

Quote:
Originally Posted by Vaevictis Asmadi View Post
I think there's an atmospheric scattering effect that obscures things at large distances. But I have no idea how far away a mountain or mountain range of a given size would remain visible.
Actually, at a great enough distance the reference mountains would subtend too small an angle to be visible above the surrounding terrain anyway, so you'd need fairly extensive charts for each area, with silhouettes for you to recognise the right mountains. I'm not sure how practical it would actually be, but I'm tending toward lower. You'd need to have fairly extensive surveying work done, which was an 1800's thing in our Earth history.
__________________
Collaborative Settings:
Cyberpunk: Duopoly Nation
Space Opera: Behind the King's Eclipse
And heaps of forum collabs, 30+ and counting!
Daigoro is offline   Reply With Quote
Old 10-28-2018, 10:30 AM   #44
Vaevictis Asmadi
 
Join Date: May 2007
Location: Twin Cities, Minnesota, U.S.A.
Default Re: [Basic] Skill of the week: Navigation

Quote:
Originally Posted by Daigoro View Post
Actually, at a great enough distance the reference mountains would subtend too small an angle to be visible above the surrounding terrain anyway,
Or above the surrounding waves, at sea. In both cases, it seems to me that standing at a higher elevation would help visibility, though probably less so on a flat world.
__________________
I have Confused and Clueless. Sometimes I miss sarcasm and humor, or critically fail my Savoir-Faire roll. None of it is intentional.

Published GURPS Settings
(as of 4/2013 -- I hope to update it someday...)
Vaevictis Asmadi is offline   Reply With Quote
Old 10-28-2018, 11:13 AM   #45
johndallman
 
Join Date: Oct 2010
Location: Cambridge, UK
Default Re: [Basic] Skill of the week: Navigation

Quote:
Originally Posted by Vaevictis Asmadi View Post
Interesting! Although I can imagine a world (not Middle-earth) where the stars are close and attached to a solid celestial sphere that rotates. In that case maybe they would be fixed enough to use windroses.
No, they won't. Have you ever been in a planetarium? Consider that large dome, with points of light projected on it from the centre. At the centre, it looks very much like Earth's sky.

Consider the point of light that represents Sirius, projected on the dome. It's above the horizon, by an angle that's correct if you view it from the centre.

Now walk to the dome wall just underneath it. It's vertically above you, the angle above the horizon is too large.

Now walk to the opposite side of the dome, and the angle is too small.

This effect is called parallax. We don't see it for the real stars because Earth is minute compared to the distances to the stars.

We can see it for the Moon; the time at which the Moon will pass in front of a star is a different moment for someone in the US and in Europe, even though they can both see the moon at the same time. The Earth has a noticeable size compared to the distance to the Moon, so parallax is detectable.
johndallman is offline   Reply With Quote
Old 10-28-2018, 02:20 PM   #46
Vaevictis Asmadi
 
Join Date: May 2007
Location: Twin Cities, Minnesota, U.S.A.
Default Re: [Basic] Skill of the week: Navigation

Ooohh, now I get it. Thanks!

Could people learn to use parallax itself for navigation? If anything in the sky is near enough to have significant parallax, might that make it possible to triangulate one's location using the angles of several such objects at once?
__________________
I have Confused and Clueless. Sometimes I miss sarcasm and humor, or critically fail my Savoir-Faire roll. None of it is intentional.

Published GURPS Settings
(as of 4/2013 -- I hope to update it someday...)
Vaevictis Asmadi is offline   Reply With Quote
Old 10-29-2018, 11:06 PM   #47
Daigoro
 
Daigoro's Avatar
 
Join Date: Dec 2006
Location: Meifumado
Default Re: [Basic] Skill of the week: Navigation

Quote:
Originally Posted by Vaevictis Asmadi View Post
Could people learn to use parallax itself for navigation? If anything in the sky is near enough to have significant parallax, might that make it possible to triangulate one's location using the angles of several such objects at once?
If the sky doesn't move, it's a lot easier. But that was exactly the trick I explained with the mountains - you're just triangulating off the sky instead of off a peak. And with a close moon passing overhead, you don't really need instruments. The moon would pass through different constellations depending on your latitude (defined here as being perpendicular distance from the moon's suborbital track).
__________________
Collaborative Settings:
Cyberpunk: Duopoly Nation
Space Opera: Behind the King's Eclipse
And heaps of forum collabs, 30+ and counting!
Daigoro is offline   Reply With Quote
Old 10-30-2018, 05:31 PM   #48
jason taylor
 
jason taylor's Avatar
 
Join Date: Aug 2005
Location: Portland, Oregon
Default Re: [Basic] Skill of the week: Navigation

Quote:
Originally Posted by Vaevictis Asmadi View Post
The Polynesian methods aren't explained other than the stick chart, and LT doesn't say whether that relies on types of currents that only exist in the Pacific.
It would have been even harder for the Polynesians then for unquestionably great seamen like Norse and Early Modern Explorers. The islands were somewhat small and there would have been a lot of hit or miss. Some probably just found something by accident and reported it back at the village or had a private net-mending station that grew into a new village ad infinitum.

Knowing how the first Polynesians to anywhere navigated is paradoxically easy. They didn't, they just happened upon it. It was how they came back that is the thing to figure out.
__________________
"The navy could probably win a war without coffee but would prefer not to try"-Samuel Eliot Morrison
jason taylor is offline   Reply With Quote
Old 10-30-2018, 06:03 PM   #49
Refplace
 
Refplace's Avatar
 
Join Date: Nov 2008
Location: Yukon, OK
Default Re: [Basic] Skill of the week: Navigation

Quote:
Originally Posted by Daigoro View Post
If the sky doesn't move, it's a lot easier. But that was exactly the trick I explained with the mountains - you're just triangulating off the sky instead of off a peak. And with a close moon passing overhead, you don't really need instruments. The moon would pass through different constellations depending on your latitude (defined here as being perpendicular distance from the moon's suborbital track).
I use this for my Chalice World setting.
The livable part of the world is bowl shaped and you can see the Barrier Mountains from everywhere on a clear day. That helps you figure how close to the rim you are. The main way to navigate however are the 4 moons which are different colors and stationary. So on a clear day or night you can see 3 or 4 moons and the sun or dark spot in the center. Likewise magic can sense the direction of the appropriate moon.
I think Navigation in this world is incredibly easy, though finding precise angles and distances would still require skill.
__________________
Looking for group in my area
My GURPS official contributions Buying them lets us know you want more!
My GURPS fan contribution and blog:
REFPLace GURPS Landing Page
My List of GURPS You Tube videos (plus a few other useful items)
My GURPS Wiki entries
Refplace is offline   Reply With Quote
Old 10-30-2018, 08:01 PM   #50
smurf
Banned
 
Join Date: Jun 2005
Location: Bristol
Default Re: [Basic] Skill of the week: Navigation

Firstly Navigation is split up into Land/Sea/Air because the techniques are very different.

Sea Navigation requires to know your speed and 'Long and Lats' which was only made easier with the Harrison's Marine Chromometer.

Air Navigation also relies on speed and direction. In many instances flying by instrument alone, knowing the spatial position of an aircraft and if able to spot land marks.

Land Navigation as noted is great when coupled with Area Knowledge. Maybe each point in Area Knowledge can add +1 to Land Navigation. The cities that we live in we may not know every knook and crany but we have a good idea where things are in relation to other things. Adding a Map makes it much easier (+4 for accurate tools plus a bonus from Area Knowledge).

For me I know that Bristol is home to many 'A roads'. A4 is the 'London' Road from Avonmouth via Bath and follows the path of the M4. A37 is the Wells road going South (forks from the A4). The A38 runs North towards Birmingham and South through Taunton and down to Exeter (follows the M5). A420 runs East through to the villages such as Devizes (in between M4 and A4), A470 is the Weston Road that will intersect the M5. The A4174 is Bristol's nigh ring road crossing the A38 in the North, travelling through: Filton, Patchway, Kingswood, Hanham, Brislington in the South and travelling inwards along the A4 before forking off at West Town Lane via Hengrove, Hartcliffe in the South and meeting up with the A38.

I have lived in this city all my life so I am familar with specfic regions but have a general knowledge of the city. I suppose this is where Dabbler can be useful because my knowledge of the South of the city is better than my knowledge of the North.
smurf is offline   Reply With Quote
Reply

Tags
basic, navigation, orienteering, skill of the week, world building

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Fnords are Off
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 12:31 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2021, vBulletin Solutions, Inc.