Shag, I've spoken my piece. I'll discuss the topic, happily. It may not go in the direction you wish, though. I'd like to better understand your goal in proposing the topic, and what you hope to gain by having a better mental model of vis distribution in the Order. Those are some valid questions that must needs be answered. I've thought long and hard about a related issue of Vis economy for a while. Just so you know where I'm coming from I see having a vis distribution model to be about like setting a money supply, and I can't see that as being productive for any saga.
The core book suggests (p. 218) 10 pawns per magus per year for a Moderate Vis level; 5 pawns for Low Vis and 20 for High Vis. With 1200 magi in the Order, this is 6000, 12000, or 24000 pawns per year that are harvested and used by the Order. Given that the area of Europe is about 10,000,000 square kilometers, this is an average density of 0.0006, 0.0012, or 0.0024 harvested pawns per square kilometer.
The question is then how much raw vis is harvested by the Order, vs. how much is available for harvesting and/or harvested by others. I don't think there is an official answer on this. My inclination is to think most of the readily available raw vis is controlled by the Order, it being the most powerful faction and ever-hungry for raw vis. However, some portions of each tribunal are under-exploited for local reasons (e.g. the Rhine Curse), and in a few regions Hermetic presence is too sparse to significantly exploit the area, and other traditions of magic would also take their own share. So I'd conservatively estimate the Order only harvests half the raw vis that is available for harvest: this means 0.0012, 0.0024, or 0.0048 pawns per square kilometer are available for harvest.
The amount that is available for yearly harvest isn't the same as the amount that is present. Some vis is too powerfully guarded, but I'd assume that the Order is so powerful that this is very rare. Some vis is present in large quantities but only a fraction can be harvested yearly; this is probably the usual case for many raw vis sources and for slowly-replenishing stocks aka creatures. Doubling yet again to account for this, we have 0.0024, 0.0048, or 0.0096 raw pawns per square kilometer, only half of which are available for harvest.
This is a rather low estimate. If you are thinking of magi are rare or weak in the setting so that most raw vis in most places isn't being harvested, then the density can get much higher.
The fact you think I want it to go into a particular direction is the thing I will start with first because it seems to be a major misapprehension by many of the participants. I don't seek and I do not care whether the end consensus of this thread is that calculating geographically distributed vis density is either useful or useless. I will post my motivation for asking the question originally a bit later as I want to give it the time it deserves. However, that motivation has no inherent bias in that I want people to say it has value or not. Nor does the motivation really relate to the vis economy, or creating a model of it, though that has a potentially interesting relationship to the geographical issue, obviously.
I don't have any idea of the direction you want it to go. I was merely stating that topics on this forum can go into tangential areas rather quickly.
I asked a question about what the average tractatus quality was, and by the time it ended we came up with a model for the numbers and qualities of tractatus that have been created in the history of the Order and batted that number back and forth.
We can try to get some extremely rough extimates for the accessible vis - as kingsreaper noted, there may be billions and billions of queens that no one but the angels knows how to harvest.
First of all, note that the Order of Hermes has 1200 members. If we look at the various covenant descriptions in Arm5, the average starting magus may get 4 pawns/year, while senior magi may get 10+ pawns. Thus, the Order probably gathers something of the order of 10000 pawns/year. Since Mythic Europe is about 10 million square kilometers, there is at the very minimum 1 pawn/1000 square kilometers/year, i.e. some 3 pawns/year within a day's journey (about 20 miles or 30 kilometers) of any given spot.
But for every Hermetic magus, there are probably a dozen or more (in remote areas, maybe even a hundred or more) various witches, wise women and other assorted hedge wizards, and they, too, consume vis - even though often in lesser quantities than Hermetic magi. So the average vis harvest is probably several times larger than the amount above, possibly even an order of magnitude larger (1 pawn/100 square kilometers/year).
Of course, this only counts what's harvested... but at the same time, given that some Tribunals are short on vis, the amount that's easily found and harvested is probably not much larger than the amounts above. Take Normandy, for example, with a size of a few hundred thousand square kilometers and a population of roughly a hundred magi. If we assume that the average density of vis in Normandy is only say, half to one quarter of the average in Mythic Europe (because of encroaching civilization), assuming more than 1 pawn/100 square kilometers/year in Mythic Europe would make more than 10-20 pawns/magus in Normandy relatively easy to find and access - which seems somewhat at odds with what we read.
So, my best guess is: the amount of vis per year from vis sources relatively easy to find and access is between 1 pawn and 1 rook / 1000 square kilometers, obviously subject to wild fluctuations.
EDIT: Alas, before I answered I just skipped reading all posts beyond the point the discussion started to get into a rather unproductive flame, and so I failed to notice the very similar numbers posted by other people (e.g. YR7, an hour ago, based on a similar line of reasoning).
The math from YR7 & ezzelino actually creates an interesting question. With Jonathan's math, where seisins are spread over 25k square miles & distributed amongst 80 magi, or 813sqkm per magus. If seisin vis distribution works out to an average of 5 pawns per magus (Low Vis, p218), then we've got a density of 6 pawns per 1000 square kilometer in the seisin clusters; and appreciably less than that in the rest of the Tribunal.
If Normandy is only slightly smaller than modern-day France, we've got 600k square kilometers. If seisin production makes up roughly half of Normandy's vis capacity, then vis source density over the entire Tribunal is roughly 1 pawn per 750 square kilometers (if seisin's make up 75% of the Tribunal's capacity, then it's 1 per 1125sq.km.).
It's stated that a the riches vis source in Normandy are in the low countries and in areas that would be part of the Lotharingian Tribunal. Should the Lotharingian Tribunal be formed taking the low countries and the eastern portion of the Tribunal, Brittany would end up producing more than the rest of the remaining parts of the Normandy Tribunal combined. That would put a number of Tropea in both Brittany and the eastern part of the current Normandy Tribunal and perhaps the low countries, too.
Uhm... what's the interesting question again?
Your first Vis Source density estimation is a minimum of 1 pawn/1000 sq km, which roughly on par with my Normandy estimation, a notably vis poor region of Mythic Europe. Both of those estimations are in regards to currently exploited Vis sources within the Order. The question is where our estimations are diverging for your overall average to be close my below average.
The genesis of this question was in a campaign where the PCs were seeking a covenant location.
Before I detail it a bit more there are a few things that should be made clear.
My campaign: Because we do not run troupe style I had a few more options than the usual SG.
Your Campaign: There is no argument here that you adopt anything discussed on this thread for your own campaign. The core rules and the supplements are sufficient for your purposes if you want to stick with that.
Nature of Sources: There are different types of vis sources, some of which might be a bit difficult to fit in a geographical distribution. Some of these are the non-aura sources where every year an apple grows and when its picked it contains vis. Clearly there are five types: auras, regios, harvest (the type that is renewed each year), dump sites (eg there is a lot of vis from dead creatures but no aura) and trace. Trace being similar to dump sites but with probably not the same concentration.
With the search for the covenant, I wanted to make it a bit more exciting than simply picking a spot on the map and than having the build points allocated so what I did was take the A4 map of the Rhine tribunal and divide it into 10 x 10 square areas, (roughly 72 x 63 miles each) and give each square a number. The players than used various lore abilities to find rumours/hints based upon a random roll of 2d10.
As the game developed I decided to mix it up a bit by randomising the covenant hook/boons in one of the GR squares. It was pointed out that this is a fairly large area to settle only 10 build points on and that is of course when I started to contemplate how common are magical auras. Of course vis sources are what the players are really looking for, though an aura is a bonus. So hence the interest in the vis distribution. The idea of using build points randomly is in fact a great way to fill the territory in the grid references quickly. I have been using a 12 x 12 hex map at 6 miles per the hex to build up a local gazetteer. I have developed a whole series of tables to do it. I am a bit of a lazy SG in that respect.
The big things that effect the presence of vis will be human changes to the natural environment, human population, the dominion etc. You can pretty much say that all three will have a drastic effect upon the natural magic sources. Obviously its a pretty hard ask quantifying them hence I have no really hard or fast expectations as to results. The interaction with the vis economy is pretty interesting as I had not given that any thought and there is going to probably be some relationship between the two...
The real issue I see with the question is that it si too modern for the game. A modern land developer gets a land survey completed, a geologist checks for potential mineral wealth, thee is a statistical analysis of potential yields...
A medieval person looks for some open land in a convenient spot hat looks good and won't cause too many problems with local nobility and doesn't have a corrupt and annoying churchman watching over your shoulder...
Do you know silveroak, we just had a very long discussion about this, so how about I just reiterate what I said at the very start for those who are now joining the thread...
HAS ANYBODY GIVEN ANY THOUGHT TO HOW THIS COULD BE QUANTIFIED GEOGRAPHICALLY?
If your answer to this is yes, than provide what your thoughts have been if you would like to do that.
If your answer is no, than no one has to say any more...
Reframe the context.
How is it quantified geographically? Look at the tribunal books. Hibernia and Novgorod are vis rich, as is Thebes. The Roman Tribunal has to struggle for vis. Within a medieval paradigm that is quantified. Additionally vis sources are not stable. A family of mythical creatures can be a wandering vis source, if not the kind you usually document in covenant creation. Vis sources can arise when you raise the covenant mana level, or be discovered or lost in myriad ways. And the fact is, that is thinking about it. Unfortunately thinking about it results in something that looks more like quantum mechanics than a geographical survey. That's magic for you.
The tribunal books have been discussed, quite a few times. And yes, I agree it is a form of quantification. I also agree that a family of mythical creatures can be a source; it is stated about two or three posts above here by myself. And if your one of your covenant boon/hooks is a creature you could reasonably imply that it was a vis source. I also agree that raising the covenant mana is a form of quantification. And I also agree that by stating all of the above that you have shown you have thought about it. Whether it looks like quantum mechanics as opposed to a geographical survey could also be an outcome to this discussion.
However, none of this was in your first post. Your post was that the process of quantifying vis sources was too modern. I will refer you to any history of surveying that shows that the process of surveying is quite ancient...
More accurately that the land-survey method of quantifying vis sources was too modern. Surveying to determine boundries was certainly ancient, but to determine resources in numerically quantifiable ways not so much. Also I never said that surveying was modern, but that the approach of choosing a location based off geographical survey was too modern.
The Domesday book recorded resources...
I think the problem many people are having is that the whole issue sounds a bit like:
"I want to know how many nuns live within a day's journey of the covenant.
Can you give me an estimate of how many nuns/square kilometer the setting has?"
Sure, one can look up an estimate of the number of nuns in 1220, divide that by the number of square kilometers of an area encompassing Europe, the middle East and northern Africa, and obtain a figure like 0.008 nuns/square kilometer (disclaimer: it's just a number I made up). And you can compute that the land area within a day's journey of your covenant is 2145 square kilometers. But that does not quite tell you that within a day's journey of your covenant one can find 0.008*2145=17.16 nuns.
If you want a large abbey with 500 nuns within a day's journey of your covenant, it's there. If you don't want a single nun within a day's journey of your covenant, you don't have a single nun. Finding out how many pawns of Herbam vis a magical forest yields is not like finding out how many bushels of rye an acre of good land yields. Any statistics one could get (and those would be very very rough indeed) for Mythic Europe or even a single Tribunal become meaningless when you zoom in to the scale of a single covenant.
It's much easier and effective to start with how many pawns you want your covenant to have available, and then decide interesting ways in which those are gained. This also leaves open possibilities not contemplated by treating vis as stuff that is "localized" (whether static or roaming): for example, your covenant might gain vis by defiling holy relics, by receiving a tithe from the Tribunal for some particularly worthy service it provides, or by having an extensive trade network covering Mythic Europe that locates and ships to the covenant grain infected by ergot (from which the covenant distills Perdo vis, and sometimes Mentem or Imaginem vis).
I think there are a number of problems that people are having. There are a number of approaches that have emerged. The negative ones (and this is not exhaustive) are as follows:
- Useless
- Valueless
- Cannot Do it
- Incalculable
- Pointless
- Meaningless
Your view falls within one of these. Since you have stated it, that can be incorporated into any final analysis. There is no problem with that.
Hear, hear. Shag is right. If you can't contribute to the conversation, at least stop being a troll (and that's exactly what your doing). However, what ever number you come up with is going to be highly subjective do to randomly chosen variables. And without any official data, random numbers is all we are going to get. That being said, in a low fantasy setting, I'd say 0-2 vis sources psm, in a medium (the standard setting) one about 2-5 vis sources psm, and in a high fantasy about 5-8 vis sources psm. These numbers were not arrived at by any analysis or mathematical calculation, simply gut instinct, so feel free to disagree with these numbers.
You don't quantify the amount of Vis, and even at 1 pawn per source, that much Vis will surpass the dreams of even the most avaricious magus. I understand psm to be per square mile.
When I designed a covenant on the top of Mont Beuvray I had 4 sources there and it was a 2 square mile area. Other nearby areas didn't have any Vis, though.
Edit: the sources were all based on real physical locations on top of Mont Beauvray.