Pokémon Go S2Cells

S2 cells is a mechanism to divide the 3D world into a 2D map. S2 cells can be represented into various levels of sizes from a square of a few meters to a square of a few hundred kilometres. A higher level of S2 cell represent a smaller square on the map. S2 cells are important to Pokémon Go players because the game world is built on top of those S2 cells. PokéStops, gyms and even EX-Raid eligibility are all determined by those cells. In this page, we will explain 3 different levels that could be useful especially with the possible ability to nominate new points of interest in the future with an in-game menu.

Level 20
Level 20 cells are the smallest cells that Pokémon Go uses. They dictate the spot where spawns/nests exist. Pokémon appear in the centre of such a spot.

Level 17
S2 level 17 cell size is quite small. In each of these cells, only one PokéStop or gym can appear. The points of interest are pulled from the game Ingress, where they are called portals. The following link https://intel.ingress.com/intel shows all available portals. Even though there are multiple portals inside the same level 17 cell, only one of them will be pulled over to Pokémon Go.

Level 14
Level 14 cells decide how many gyms exist in a cell. The following table shows when PokéStops are converted into a gym. For example, when there is only 1 PokéStop in one level 14 cell, it will not become a gym. However, when there are 2-5 PokéStops in the same cell, then one of those PokéStops will be randomly chosen and converted into a gym.

Level 13
A gym can only become an EX gym when it is located inside an OpenStreetMap park tag. All the areas that are coloured green are parks. There could be several EX eligible gym in the same area, but the S2 level 13 cells decide how many EX gym can be triggered. You can see the Centre-GCB zone overlayed with S2 level 13 cells. In each cell, only one EX gym can be triggered.

Additional sources
You may find additional sources in the Pokémon Go link itself.

For a more detailed breakdown of the S2 cells system, please read up on the following link. Pokémon_Go_S2CellsPokémon_Go_S2Cells