Hi

would somebody be kind enough to point me to technical articles that explain how a vehicle nav system is able to compute routes between A and Z. basically, i want to understand the algorithms (or heuristics?) that are used.

there has to be some way to determine how much each of (say) the 4 roads leaving "A" improves (or degrades) my "current" route to Z. (and how is that initial route computed??) i assume that there is a quality assigned to each branch leaving A, in terms of whether it increases, or decreases, some "score" for the A ro Z route. and ditto at the next intersection. but this would make my choices multiply rapidly (like chess), even excluding obvious redundancies. so there has to be a pretty effective path-culling calculation, too.

now to the practicalities.

once i have left "A", if i deliberately diverge from the calculated route, my device keeps trying to force me back to (say) highway 1 at intersections C, D, E, etc.

Each of these corrections seem to be optimal in a "micro" sense - they expeditiously get me back on the calculated route - but these corrections are generally suboptimal in a macro sense - i.e., there are better ways to get to Z, *given where i am now*. in other words, it "corrects" me with the two legs of a right triangle, because it cannot "see" the existence of the hypotenuse.

eventually, as i get close to Z, or if i am nearing a choke point such as a bridge where everything converges, my device stops trying to force me onto its intended route, and appears to recompute a best path from my current point to Z.

i know that's long winded, but i hope i've expressed myself.

again, thanks to any and all help; dont hesitate to point me to dense technical or mathematical stuff; i should be able to absorb it.

Vasco