What the calculation is based on
People operate where they're familiar. Home-work-store routes outline a territory they know, and the overwhelming majority of a person's activities happen within it, rather than at a random point in the city.
That leads to the first rule: the farther from the base, the less often activity occurs. Activity falls off with distance because a long trip takes time and increases the risk of getting lost in an unfamiliar area.
How points are distributed by distance from the base: a dip right near home, a peak farther out, then a decline. This is the shape of a pattern, not data from a specific case.
The dip right near home is called the buffer zone. Close to the base, there's too much chance of being seen by people who know you, so the nearest blocks are usually avoided.
What the method can and cannot do
The result is not a name but a map of probabilities: an area where it makes sense to start checking. The method narrows the search area and changes the order of checks, nothing more.
It only works with a series of points. One point tells you nothing, and two tell you almost nothing; the calculation becomes meaningful when there are at least several points and they belong to the same person - which still has to be proved.
Ordinary things can also disrupt the picture: moving in the middle of the series, a job that involves frequent travel, or a river or railroad that makes actual distances differ from straight-line distances.
The same mathematics has long been used for peaceful purposes. It helps locate the source of an outbreak from the addresses of people who became ill, estimate where pests are spreading from in fields, and plan where to place a service center.
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Sources
- Geographic profiling relies on models of spatial behavior: activity declines with distance, with a buffer zone around the base. The method prioritizes areas for the search and cannot identify a specific person
- its accuracy drops when someone moves, has a travel-heavy lifestyle, or operates within a complex transportation network. Similar models are used in epidemiology and ecology