The market for electronic alternative to paper maps has gone bonkers over the last year or so, with the choices in dashboard navigation expanding greatly. Road and Track does an excellent job of sussing out the differences between various types of aftermarket nav systems, from in-dash to on-dash to those based in a personal electronics device like a Palm device or laptop. The main similarity in the systems is their use of Global Positioning Satellite coordinates to translate the car's global position to a position on a digital map. The systems also work in real time, refreshing as the car travels, so they can remind you when to turn. The drawback of electronic mapping is that there's a computer at work, and computers don't always operate according to what humans would consider common sense; for instance a nav system will compute the shortest possible route, but regardless of the relative ease of that route, using any available shortcuts, U-turns or zigzags. But for the most part, the article concludes, the nav systems are still more reliable than human navigators.