Wandering way home

I'm working at an office about 4.5 km as the crow flies.( from where??) Once or twice a week, I walk back to my house.
I have a couple of regular courses, but sometimes I turn  a corner on impulse, and walk out of these ways. I try to go back home on foot relying on guide plates (?)and my sense of direction.

Sometimes I walk back home successfully, sometimes I can't.
When I find myself still far from my house after walking two hours or so, I go back my house by subway.
Subway stations are everywhere in the urban area of Tokyo, so I can wander on my way home after work comfortably.

You cannot say "as the crow flies" without stating from which point.

I don't know the meaning of "guide plates".