Can I use a Google map in my PhD thesis?
Google provides you the right to employ a Google Maps map on your thesis. See Permission Guidelines for Google Maps and Google Earth (first two points of The basics and Using maps in print).

However, they ask you to provide correct attribution for those pictures. It will be something like “Map data ©20xx Google, Sanborn”. As they write, you have to find the correct copyright statement on the map you would like to reproduce in your thesis.

Alternatively, it may be possible for you to use  OpenStreetMap which is Open Data material and has more permissive licensing.