Originally Posted by
Nihilum
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.
The gist of your post is correct: You can use many smart phones as a GPS navigation device for bicycle without using any cellular data, but some details aren't quite right.
Most modern smart phones
can store maps on the phone, but this is not the default behavior for Google maps (or Apple Maps) as far as I know.
GPS is not from terrestrial towers, but satellites. But you are correct that it doesn't use cell data. And no smart phones have "internal drives", but do have flash memory and some have removable SD cards.