Most modern smart phones do not download maps as they go...the information is stored on the device. The phone itself gets GPS location through triangulating through multiple terrestrial towers...it's not using data. You have to keep in mind that a lot of today's phones have huge amounts of storage. I have road maps for the entire US, Canada, Central/South America, Europe, Scandinavia, Australia, and most of Asia. Whole thing only uses a couple of Gigabytes of storage...on a phone that totals over 50 GB with internal drive and removable SD card.