Here is a SUREFIRE way of not making mistakes - with the caveat that you are still relying on inevitably flawed map data.
Plan your route ON your satnav.
Simply put = minimal coq-au-vin moments.
Reading so many satnav related issues on here and elsewhere there seem to be a huge reliance on second/ third/fourth and Lord knows what software/gadgets, then add in some converters, making a right soup of what is a basic job.
Each of those inevitably introduce layer upon layer of potential errors giving rise to the 'it doesn't look anything like on my computer' headaches.
Seems to me that many have forgotten the 'KISS' principle but if that is what floats your boat- paddle on!