Difference between revisions of "PolarCompass"

Revision as of 01:17, 6 April 2010

Pinpointing your location at sea without high technology in our world requires, among other things, magnetic north, which doesn't exist in Exalted. And, since Creation isn't a globe, the concepts of latitude and longitude don't exactly mean the same thing. Savage Seas spends nearly a page describing an arcane mechanism supposedly employed by navigators in Exalted. This aims to do a bit better.--Wordman

The hand held polar compass (artifact •, 0 mote commitment) contains a number of needles mounted on a single central pivot, suspended above a radial legend that allows the measurement of the angle between the needles. Each needle is made of a specific color of jade and always points to the elemental pole associated with that type of jade. Most polar compasses contain five needles, one of each type of jade. Some more "mass-produced" compasses (Resources ••••) may be made with as few as three, however, as only three different colors are actually required.

For any given point in Creation, only one configuration of needles is possible. So, by examining the configuration, and doing a little math, you can exactly pinpoint your location. This is possible because the poles are laid out along two intersecting lines and are a known distance apart. The "Air-Fire" line runs north to south through the pole of Earth, while the "Water-Wood" line runs west to east, also through the pole of earth. Knowing that these two lines intersect at right angles at the pole of Earth, the angles between three of the needles can be used to triangulate both how far east or west you are from the pole of Earth and how far north or south, provided the three needles don't all lay right on top of one another. (It can be assured that at least one pair of needles will have a readable angle only if at least one points to a pole on the "Air-Fire" line and at least one other points to a pole on the "Water-Wood" line.)

http://rpg.divnull.com/exalted/images/polarcompass.png

To find any exact position, the reader must do the math using an Intelligence + Lore or Intelligence + Sail test. Five successes pinpoint location exactly. Fewer successes reveal the location with lesser and lesser accuracy. Such tests are usually impossible to make without access to books of trigonometry tables or some form of computation artifact, and making a test without these increases the difficulty by four. Larger compasses (still artifact •, but not portable), such as those used by the Imperial Navy, provide more accurate angle measurements, and so add three dice to this test, but only if the aforementioned sine tables are present.

There are also a few "shorthand" methods of measurement that do not require a math test. One is to place the compass on a correctly scaled map of Creation and move the compass around until it rests in the location where all the needles point at their corresponding poles on the map. Once done, the spindle of the compass marks your current location on the map. This requires a fair amount of eyeballing and depends on the accuracy of the map, but generally gives results equivalent to a one or two success math test. The more needles the compass has, generally the better the result will be.

Books also exist containing tables that tell you where you are for a given combination of angles. The number of combinations is essentially infinite, however, so such books will usually only contain data for set intervals, usually a resolution of five degrees. Using such books automatically provides the equivalent of one or two successes on the math test.

Important ships in the Imperial Navy generally have more advanced versions of the polar compass that do the math automatically (artifact ••, 1 mote commitment). These communicate position either with some kind of illusion of Creation, writing floating in space, projecting a point of light onto a map, or planting the information directly into the mind of an attuned user.

Math

If anyone wants to show an example of the trig, be my guest. Maybe I'll do it later.

Comments

This is beautiful, Wordman. Don't have Savage Seas (or any other book) in front of me at the moment, so I have a question. Do you think this makes navigation more or less difficult for the average sailor to get around? Or rather, do you think the Exalted developers wanted navigation to be handled this simply and easily? Yes, the math is rough for these folks to do, but you can still get an amazing knowledge with just a few successes, definitely more knowledge than us Reality folks can do with a magnetic compass. --UncleChu

Yep. Having five points of reference is much better than having only one in Reality. Even better than GPS, actually. You don't even need a clock like we do. I think this certainly makes it easier to navigate than the freaky system in Savage Seas. As for intent, I'm not sure. I sort of get the impression that the writer was kind of locked on the idea that a compass would point to the elemental pole of Earth instead of north, and built the whole section on the ramifications of that one idea, rather than, say, thinking of the five-needle compass, then rejecting the idea becuase it made navigation too easy. I'm just speculating though. -- Wordman

Given the instability of Creation near the poles, won't the four non-Earth poles show severe fluctuations during Wyld storms, or even during different moon phases? --Ialdabaoth

That isn't my impression, but I'm not sure. I always thought the poles were very stable pockets of reality. -- Wordman

I'm kinda with Wordman. Just because the Wyld surges and crashes around the poles, it certainly doesn't consume the poles, or all of Creation would become unhinged. The Greatest Elemental Dragons chill there, and that alone is probably enough to keep the poles rooted in one place. Perhaps the compass would get furked if one were actually IN the Wyld, but so long as it remains in Creation proper, it will probably sense the Poles regardless of what lays between. --UncleChu who just flipped through both Cores, GoD, and Lunars to make sure he knew what he was talkin' about

On the other hand, we are told that Creation was once larger than it is now, which suggests that the poles may have moved a some time in the past. This might have been a one-shot, calamatous event, though. - Wordman

On the third hand, perhaps the poles never moved out, and Creation extended past them. The elemental purity was tamed with magic. Imagine some great metropolis, and in the center, walled off, is a huge column of pure fire extending all the way to the heavens. The Defense Grid the Empress activated extended to the Poles, the default borders of Creation, and the artificial Creation beyond that was stripped away, an elemental borderlands being gnawed at by the Wyld. This idea could explain the ancient texts and fixed math.

Or maybe the Poles do slide in and out with the expansion or shrinking of creation, and the compasses are just plain magical.--UncleChu

Personally, I'd feel better if a wood-compass always pointed due East, as if the Elemental Pole of Wood were infinitely far away, and likewise with the remaining three - with only the Elemental Pole of Earth being a 'known fixed point'. The accepted layman's definition of the "elemental pole of Wood", then, or any similar suchness, is simply the furthest point of Creation that currently exists in that direction.-Ialdaboth

If you do that, however, your angles will change as the size of Creation changes. Which is all well and good (and I probably agree with you), but it'll definitely render First Age records of "set needle directions" inaccurate. If you take a triangle and slide one of the corners farther away, angles change. You could still calculate distances from the Water-Wood and Air-Fire lines, combination books and maps would have to be rather recent to retain accuracy for the current pole positions.--UncleChu

I think the writer of the Savage Seas navigational method is assuming that the Elemental Poles are infinitely far away from each other. That is, a Wood-Fire compass will always give a 90 degree angle regardless of where in Creation you are (at least until you actually reach the Elemental poles). If we go with this assumption, then the polar compasses can't determine actual location without some sort of secondary reference point. Hence, the method described in Savage Seas. - TonyC

Not exactly true. The polar compass, in this case, would give you something that the Savage Seas compass would not: a perfect indication the relative angle between the pole of earth and the "grid" of longitude and lattitude. This would be vastly more helpful than the Savage Seas system. In that system, you know the direction of the pole of Earth, but not your own orientation. This means that you could draw an infinite number of lines between the elemental pole of earth and random positions on a map, and you could be on any of them. Since the polar compass would, in this case, show your orientation to the grid, there is exactly one line that could be drawn from the elemental pole that uses the angles shown on the compass. True, you wouldn't know how far you were from the pole of earth, but you'd know you were on that exact line somewhere. Also, since you know the orientation of the grid, you could move along it exactly. If you happen to know your speed, you could take measurements several hours apart and triangulate your position based on the change in the angle to the elemental pole of earth. -- Wordman

The Savage Seas method uses the North Star instead of another elemental pole as the reference point. I will grant that a polar compass will quite handy when the North Star isn't visible (during daylight, for example), but beyond the increased utility, this is no different from the method described in the Savage Seas. Mind you, if the Elemental Poles have fixed and known distances from each other like you assumed, then the polar compass becomes THE navigation method. On the other hand, if they are infinitely far away, Savage Seas. - TonyC

I wonder what happens when the sidereals move the North Star. -- Wordman, whose mind is still exploding from the line saying that all stars but the North Star are "too far away to be much of a help with navigation" in Savage Seas.

if you take a gander at bastions of the north you miht notice that opal spire was once a terraforming location, within creation, that is now at the elemental pole of air. i.e. the pole seems to be the last point of creation before it becomes deep wyld, and thus moves. With the system described above, this would make polar compasses good for approximation - i would expect the yearly flux to be relatively minor, giving an inaccuracy of, oh, +/- 100 miles - except at calibration, of course, when everything goes crazy: and thus rendering old map references obsolete. (hey, kids! gimme an extended lore test to figure out where that is today!) so it could give you a rough location, good for open sailing, which you refine with the earth/north star method. - Molikai

In cases where the poles are a finite, but moving, distance away, calibrating the compass isn't difficult. All you need is a polar compass at two fixed points a known distance apart (say, either side of the Blessed Isle) and the ability to coordinate an exact measurement time. With this you can use the angles and the known distance between points to locate the current positions of the poles. The difficulty is in disseminating this information, and its ramifications. At the very least, the positions would need distributed to everyone in a timely manner, and table books may need reprinted (depending on how you wrote and used them). In this case, an organization with the resources of the Realm has a huge advantage and this could be an explanation of superior naval power. Of course, the Resplendent Personal Assistant in the new Wonders of the Lost Age, which shows not only direction of the pole of Earth but its exact distance away, makes most of this moot anyway. -- Wordman

Second Edition makes repeated reference to the Fair Folk and the Wyld being "beyond" the Elemental Poles. This suggests that they are canonically in fixed positions, not an infinite distance away. First Edition suggests the opposite, saying the Wyld is "between" the poles. - Wordman