Is there any research direction which is closely related with map reading? I like maps very much, any common maps, geographic, historic, statistic, etc., or I would say reading maps is my favorite hobby. I can sit at table and read maps for several hours without any stop. 

I was studying courses about math and physics in university. I am planning to pursue a PhD degree in the future. It would be great if I can convert or leverage the my map hobby as my career.

So my question is, considering my background, Is there any research direction which is closely related with map reading? If difficult to find such position in academia, is there any jobs in industry can greatly fulfill my idea?
Since I'm not really sure what is available in the GIS field for research I won't try to answer that part, but when I was in university I did some consultant work for a GPS company called baseline geo. 

They had me in to help with some database stuff, but much of what they did seemed to be making custom gps/gis maps for various clients. For example they might have a client who is a fisherman that needs a map of all his fishing areas, or where his traps are. Another example could be a wildlife preserve where they need to keep track of the animals with gps trackers in realtime. Either way it would fit both your skillsets. This is just a industry example and you seem to me more looking for a research position or ideas.