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Old 10-23-2018, 07:15 PM   #31
whswhs
 
Join Date: Jun 2005
Default Re: [Basic] Skill of the week: Navigation

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Originally Posted by jason taylor View Post
The Pundits (spies for the Indian Political Service) were trained to count standardized paces for cartographic purposes. Basically an adaptation of a military cadence. How much can be done with this?
That's a low-tech method of Mathematics (Surveying), not of Navigation (Land). It's probably "improvised equipment" for that purpose. I'd guess it's good for figuring distances, but not much help for elevations.
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Old 10-23-2018, 10:25 PM   #32
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Join Date: Apr 2005
Default Re: [Basic] Skill of the week: Navigation

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Originally Posted by johndallman View Post
Hyperbolic Navigation is a TL7 radio navigation technology that's gradually replaced by GPS at TL8. There's no mention of it in Basic or High-Tech that I can find. As far as I can see, it gives a bonus to Navigation like GPS, although this requires familiarity with the receiving equipment, and maybe an Electronics Operation/TL7 (Sensors) roll.
Hyperbolic navigation relies on relatively accurate maps and/or longitude/latitude calculations. For simplicity, just fold these systems into the generic bonus for improve equipment at higher TL. Practically, the various systems were tricky enough to use, and vulnerable enough to jamming and atmospheric effects, that Electronics Operation skill might be needed to properly take advantage of them.

Simpler Radio Direction Finding navigation aids might give the same benefit as a compass, but only to travel "on the beam" towards - or away from - the source of the radio signals. Critical failure means that you travel away from the source of the signals when you mean to travel towards it, or vice-versa. (See the story of the B-24 Liberator "Lady Be Good" for a tragic example of RDF gone wrong. For an example of critical failure/Serendipity advantage in real life, see: http://aircrewremembered.com/capture...htfighter.html)

If you want to get fancy, allow the various techniques to be improved as Average techniques based on Navigation/TL6-7, with Electronics Operation/TL (Communications) as a prerequisite.
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Old 10-23-2018, 10:37 PM   #33
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Join Date: Apr 2005
Default Re: [Basic] Skill of the week: Navigation

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Originally Posted by Vaevictis Asmadi View Post
Why is is there no default from land Navigation to Astronomy? In low-tech, Astronomy is useful for Sea and Air Navigation, so why not for land?
Often, you can't see the sky when using land navigation, especially if you're in built-up areas, woods, or mountains. OTOH, in terrain where you can see the sky clearly celestial navigation is entirely possible using land nav, so Astronomy/TL should give a default.

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Originally Posted by Vaevictis Asmadi View Post
Also, on a flat world with no curvature nor horizon, would any of the defaults between specialties and other skills change? In particular, how would that affect defaults from Navigation to Astronomy?
I'd give an unfamiliarity penalty when navigating on an oddly shaped world, as compared to the sort of world you're used to. Those penalties would carry over to attempts to use skill defaults. For really weird situations, just create a new specialization of Navigation, like Navigation (Discworld) or Navigation (Astral) and let it default to the most similar RAW Navigation specialty at -4.
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Old 10-24-2018, 11:04 AM   #34
jason taylor
 
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Default Re: [Basic] Skill of the week: Navigation

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Originally Posted by whswhs View Post
That's a low-tech method of Mathematics (Surveying), not of Navigation (Land). It's probably "improvised equipment" for that purpose. I'd guess it's good for figuring distances, but not much help for elevations.
And if the trail was to steep the pace would have to be altered. Of course a trail that rough would bear little traffic.

The Pundits tended to disguise themselves as Holy Men. It explained why they were strange travellers with a foreign accent. And surveying equipment was disguised as such things as prayer wheels.
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Old 10-24-2018, 12:42 PM   #35
Harbinjer
 
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Default Re: [Basic] Skill of the week: Navigation

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Originally Posted by Pursuivant
I'd give an unfamiliarity penalty when navigating on an oddly shaped world, as compared to the sort of world you're used to. Those penalties would carry over to attempts to use skill defaults. For really weird situations, just create a new specialization of Navigation, like Navigation (Discworld) or Navigation (Astral) and let it default to the most similar RAW Navigation specialty at -4.
Alternatively, there could be planetary or astronomical features that would give a bonus to navigation. Prime example of this is the North Star which arguably gave the northern hemisphere a huge boost to low-tech navigation, leaving the southern hemisphere, with no comparable "south star," in the dust.

Also, something I was considering for my own fantasy world was a ringed planet. How cool would that be, I thought. Until I realized that even school children could always know their latitude, everytime, all the time, night or day (excepting rare occlusions). Longitude is still trickier, but the planet-shadow cast on the rings would act as a sundial most nights, pinpointing the position of the sun, and thus the hour. That plus some astronomy would be enough to get longitude. I decided I didn't want to make thigs so easy for my players.
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Old 10-24-2018, 09:00 PM   #36
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Default Re: [Basic] Skill of the week: Navigation

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Originally Posted by Harbinjer View Post
Alternatively, there could be planetary or astronomical features that would give a bonus to navigation. Prime example of this is the North Star which arguably gave the northern hemisphere a huge boost to low-tech navigation, leaving the southern hemisphere, with no comparable "south star," in the dust.
Well, the Southern Cross's major axis points to the South Celestial Pole and is 4.5 spans of that axis away, so Antipodeans aren't left totally lost.

On a discworld, there is no horizon until the edge, so any major mountains would be visible from anywhere on the surface, with enough atmospheric visibility. They should make easy landmarks. If you have two visible reference mountains, triangulating to them will give your direction, then triangulating off their height will give your distance. Civilisations might have a grid of reference marker towers for the same effect.
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Old 10-25-2018, 06:54 AM   #37
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Default Re: [Basic] Skill of the week: Navigation

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Originally Posted by Celjabba View Post
There are several airliner pilots who landed at the wrong airport as recently as a couple year ago. So even TL8 navigation aid won't prevent all mistakes. :)
Agreed, but given the number of commercial flights events like that are so rare that it's the GURPS equivalent of rolling 3 or 4 18s in a row and best left for situations where the GM really wants to mess with the characters.

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Originally Posted by Celjabba View Post
I can attest from personal experience that if you are dead tired, you will make idiotic navigation mistakes even when GPS, Compass and map tell you you are wrong.
Additionally, poor visibility can be a factor even when you're just using dead reckoning and not trying to get your bearings by looking at the lay of the land, especially if your maps/log tables/whatever are printed in itty bitty type.
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Old 10-25-2018, 07:19 AM   #38
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Default Re: [Basic] Skill of the week: Navigation

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Originally Posted by Daigoro View Post
Well, the Southern Cross's major axis points to the South Celestial Pole and is 4.5 spans of that axis away, so Antipodeans aren't left totally lost.
There's also a dark nebula called "The Coal Sack" right next to the Southern Cross, which makes it even more obvious in a clear night sky which is relatively free of light pollution.

Additionally, there are several bright stars which can be used as "pointers". By drawing two imaginary lines from the stars in the southern cross to the pointers, you can get fairly close to finding the SCP just below the point where the imaginary lines cross. Once you know the trick, it's no harder than finding Polaris by following the line formed by the stars at the "end" of Ursa Major/Big Dipper.

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Originally Posted by Daigoro View Post
On a discworld, there is no horizon until the edge, so any major mountains would be visible from anywhere on the surface, with enough atmospheric visibility. They should make easy landmarks. If you have two visible reference mountains, triangulating to them will give your direction, then triangulating off their height will give your distance. Civilisations might have a grid of reference marker towers for the same effect.
Cori Celesti is generally visible from flat areas on the Disc. Additionally, currents, winds, and light follow somewhat predictable patterns as the Disc spins. It might be possible to determine relative distance to Hubward by observing how the light flows

In later Discworld books, Clacks towers might make handy landmarks in relatively civilized regions.
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Old 10-27-2018, 10:01 AM   #39
Vaevictis Asmadi
 
Join Date: May 2007
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Default Re: [Basic] Skill of the week: Navigation

Everything posted so far has been helpful, thank you all.

Does anyone know if GURPS Discworld discusses Navigation?

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Originally Posted by Daigoro View Post
On a discworld, there is no horizon until the edge, so any major mountains would be visible from anywhere on the surface, with enough atmospheric visibility. They should make easy landmarks. If you have two visible reference mountains, triangulating to them will give your direction, then triangulating off their height will give your distance. Civilisations might have a grid of reference marker towers for the same effect.
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.

The world I'm attempting to represent in GURPS is Middle-earth, which was flat until the drowning of Numenor. Nonetheless, Elves and Humans sailed and explored across the middles of oceans. Tolkien implied there was a sort of atmospheric blurring effect at large distances, though, at least for sighting mountains at big distances

Over Middle-earth, the stars and planets are (or look) identical to ours, and the Sun and Moon at least look like they're at the same apparent size, although I'm not sure of their distance -- they're much, much smaller and closer than the real sun and moon. But that gives the moon going through the constellations, the North Star and Big Dipper, and potentially also the Southern Cross, if all the stars (for the season and time of night) are visible from all points on a flat world.

Another flat, low-tech world is one I invented. It isn't perfectly flat, it has a very slight curve. It also has currents of cold and hot water in the oceans that could be mapped and used as reference points, especially with thermometer-like tools. I never decided what the sky looked like, so I could give it features that would help. What sorts of features would make the sky more useful on a flat world?


It seems like how much Astronomy relates to Navigation (Sea) on a flat world really depends on what's in the sky, and how it moves. My uneducated guess is that visible suns, moons, and stars would still indicate direction even on a flat discworld, but not longitude or latitude.

I am interested in getting the details right in GURPS. 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? 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. LT isn't clear whether or not these "astronomical aids" make an Astronomy default possible. Celestial navigation does allow the Astronomy-5 default but seems to be all about determining latitude. It isn't clear to me whether dead reckoning is possible on a flat world, or whether it makes ocean crossings feasible. 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.
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Last edited by Vaevictis Asmadi; 10-27-2018 at 10:36 AM.
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Old 10-27-2018, 11:02 AM   #40
johndallman
 
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Default Re: [Basic] Skill of the week: Navigation

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Originally Posted by Vaevictis Asmadi View Post
Does anyone know if GURPS Discworld discusses Navigation?
Not very much. The most useful thing for your purposes seems to be:
Quote:
Originally Posted by Discworld p. 69
Navigation/TL0 (look at the stars and consider your instincts about your surroundings) isnít much like Navigation/TL4 (employ a fancy astrolabe and lots of charts).
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