Your assumption is that GPS is required to know where you are. But each cell tower has a well known physical address and your phone connects to multiple towers

Your assumption is that GPS is required to know where you are. But each cell tower has a well known physical address and your phone connects to multiple towers making it trivial to triangulate your location. Much less exact than GPS and highly dependent on cell density, etc. https://worldwide.espacenet.com/publicationDetails/biblio?CC=US&NR=5519760&KC=&FT=E&locale=en_EP# https://worldwide.espacenet.com/publicationDetails/biblio?CC... But even just the connection cell tower number is enough to determine whether or not you're at home or work.