Re: Why not just leave the satellites on the ground, where you can go and fix them in a van...
With an OS map there is no calculation required, just visibility out to the required landmarks and one working eye.
Never heard of anyone driving up a flight of steps and through an active worksite when working from a map either. Nor having a strident voice demanding in increasingly hysterical tones that I drive into Manhattan despite having set waypoints to prevent that very disastrous routing beforehand.
I might very well have had the same trouble with barricaded Washington DC roads not shown on a map either, but then I wouldn't have planned a route through DC in the first place.