It's not a precise tool.
Maybe the more expensive ones are.
I used to do a bit of courier driving with two big boxes of maps always in the back of the van.
I eventually got a sat nav on my mobile phone and it was great.
One little phone against 2 boxes of maps a big difference.
It used to be a bit of a nightmare on large roundabouts with them but that was about 7 years ago and I would imagine that they have improved since.