I lined up the GTA V coordinates with the GTA VI coordinates found

Does Teaser Video Show Location For GTA 6?

Development footage of Grand Theft Auto 6 has leaked (Source code potentially in hands of leaker), Page 63

GTA 6: Everything we know so far

leaflet - GTA V coordinates to LatLng - Geographic Information Systems Stack Exchange

Bus Routes - GTA 5 Guide - IGN

So people used the coordinates seen in the leaks to map out the known locations. This is what the map looks like in comparison to GTA 5's map (including water). This isn't

GTA VI map is huge, according to the GTA mapping community - Jaxon

GTA 6: Release Date, Leaks, Rumors, Gameplay, Map, Characters, and More

Possible GTA 6 map size calculation : r/GTA6

Coordinates for real life location of the video leaks, and some pictures from the ground. : r/GTA6_NEW

GTA 6 map is 50% bigger than GTA 5 reveals new fan calculations