The literature has treated cell towers as isotropic light bulbs since 2008. They’re really not (that’s why sometimes you don’t have a mobile phone signal!).

Left: Voronoi tessellation of 1,292 BTS across Santiago (R13), ~6 km window over the downtown core. Each tower owns every point closer to it than any other mast, with 360° coverage assumed.

Right: the same towers, drawn as directional sector wedges built from the azimuth field that has always been in the catalog. Most masts carry three antennas radiating ~120° beams; a few carry six.

Dropping the isotropic assumption pulls the median effective radius from 504 m to 375 m region-wide, and from 245 m to 181 m inside this window. Sub-kilometre spatial resolution from a column already in the data.

The black gaps in the right panel are not missing values. They are the map being honest about where no antenna is aiming.

I’m working on a series of blog posts and “spinoffs” of this paper:

Ferres, L., & Elejalde, E. (2026). Systematic biases in mobile phone mobility data from heterogeneous tower density. Zenodo. https://zenodo.org/records/19484460

Next, I’ll try to explain the statistical methods we used, and how we can correct the values.