That system of vector maps is in popular use atleast since the 1970s, so when Google maps started, they could just collect existing gis (geographic information systems) maps. I wasn’t born yet, but I expect that countries/companies started digitizing their old maps in the 1970s and 1980s and that paper prints after that were based on those digital versions. And countries without good maps to start from (too large/remote/administratively weak), probably started their digital mapping projects based on aerial photos. And when Papua New Guinea finally starts with a digital mapping project, they can start straight away from satellite photos :)
That system of vector maps is in popular use atleast since the 1970s, so when Google maps started, they could just collect existing gis (geographic information systems) maps. I wasn’t born yet, but I expect that countries/companies started digitizing their old maps in the 1970s and 1980s and that paper prints after that were based on those digital versions. And countries without good maps to start from (too large/remote/administratively weak), probably started their digital mapping projects based on aerial photos. And when Papua New Guinea finally starts with a digital mapping project, they can start straight away from satellite photos :)