Players might see a radically different map this morning when they log into Pokemon Go.
Yesterday, Pokemon Go switched the source of their overworld maps from Google Maps to OpenStreetMap (OSM), an open source, editable mapping project. This caused massive changes to the map overnight, creating more detailed overworld maps for some users and nearly blank maps for others.
The changes seems to be taking place country by country. The switchover hit in Europe and Japan first, but American players eventually saw the switch late last night.
It's unclear why Niantic switched from the Google Maps API to OSM. While some developers have to pay a licensing fee to Google for use of their API, Pokemon Go hypothetically qualifies for Google's free plan as the game is free to play. However, OSM is editable by anyone, which means that players who notice inconsistencies in Pokemon Go can edit the OSM map accordingly to fix the issue. Also - OSM's edits are immediate, which means that Pokemon Go wouldn't have to wait for Google Maps to release a new version of their map before players can see additions or subtractions in the game.
We should also note that Niantic was spun out of a Google Maps project, and Google invested money in Niantic to fund the creation of Pokemon Go. So, this switchover could indicate a break between Google and Niantic...although that's purely conjecture.
Of course, OSM has its flaws too. While the map added a lot of detail for some users, players who didn't live in an area mapped by an OSM user immediately noticed a severe drop in quality of the map of their area. And while players who live in an undermapped area can edit OSM, that's a lot of time and work for a Pokemon Go player who just wants to catch Pokemon.
Since PokeStops and Gyms are tied to real world coordinates rather than tied to any particular map, the mapping switch shouldn't affect placement of any game locations.