I am aware of how to calculate mileage or distance by way of the "great circle" calculation but I'm really wanting to take this a step further and do so via map data.
I'm not interested at this time in displaying or showing maps, etc. although I may get to that later. All I want right now is to be able to enter a starting and ending point say zipcode and get a fairly accurate (+/- 10%) mileage calculation based on roads, my problem is I have no idea where to start.
I have downloaded the navteq transportation sample data but its pretty greek at this point so any helpful pointers or direction would be appreciative.