What determines where XM is generated?

Solution 1:

XM is generated:

1. Always around portals

2. Conspiracy theory - I believe Niantic labs is using one of the google location based services (maybe mobile maps or something more fun like g+ posts/connections) to estimate the traffic and put more XM there where people go (not only go but spend a lot of time). What I noticed:

   • Busier train and bus stations generate more XM
   • More XM is generated close to crossings (where people have to stay and wait for the green light)
   • Almost no XM is generated along the roads (which have an intensive traffic and drivers are often using phone navigation etc)
   • Somehow there is relatively few XM in public parks (at least in Germany)
   • Almost no XM along the train rails (looks like XM is generated only on slow moving/standing people)

Notes about XM:

• One unit of XM is represented by 3 white dots which are moving around the center of XM unit
• In order to suck in an XM unit a player must have an invisible XM unit center inside his action range
• XM units seem to have different energy potentials ranging from 25 to 55
• Yesterday I observed a train station platform of a middle size town, not so much traffic but enough (rush hour maybe 100-200 people standing there), XM was spread over platform unequally and was concentrated close to the underground entrance to the platform (where most of travelers stand and all of them go through)

Solution 2:

According to some investigations :

The general summary of the story so far is that during the Higgs-Boson experiments, a new energy form was uncovered, which researchers named Exotic Matter, referred to as XM in the game. XM was different in the fact that not only was it everywhere in the world, it seemed to have a sort of intelligence behind it, causing it to gather in more densely populated areas and even seems to affect the thought processes of those nearby. Further research through the Niantic Project revealed that there is some sort of being controlling the XM, a creature known as The Shaper, but not much else has been uncovered about this being.

There is obviously a link between population density and XM, but I can't find exactly what it is.

What I have observed in my town :

• XM can be found around portals (probably where you can find the most)
• XM can be found in front of shopping centers
• XM can be found at bus stops
• XM can be found in pedestrian street
• XM presence is mostly correlated to WiFi spots (probably detected by Google cars)

But I also find XM (less) in other places :

• XM found along a road (~50 XM)
• XM along a railway track (not near a railway station) (~50XM)
• XM found near some "normal" houses (~50XM)

EDIT:

Whatever the rule was, the XM locations are now fixed. Since I started to play Ingress, XM never moved. Everyday I'm sure to find XM where I found some the day before.

EDIT (25/02/2013) : Following the arrival of new portals last friday, new XM locations were added too.

(I'm curious to know if XM can be found in front of Apple Store....)