Navtech uses the TIGER data as a basis. They employ hundreds of drivers with GPS recorders and whatnot, to plod the roads regularly to add directional data and more. They use satellite maps and whatnot to improve the accuracy quite a bit. As you can expect this is pretty expensive to maintain... They seem fine with the idea that if you can't meet the minimum 10,000 units, just find either a company to sublicense, or band together with other interested people (like 5 smaller projects that need 2000 units, etc).

Calvin