Originally Posted by
KH0456
They aren't true GPS units and get the location by triangulating from cell towers.
This is wrong.
Smartphones have GPS receivers and work fine without any access to cell towers.
GPS is a bit slow to get an accurate initial fix. The triangulation helps with that.
Smartphones can also use wifi to assist in getting a fix (there are databases of wifi networks associated with location).
Once an accurate fix is obtained, GPS on smartphones is fast and very accurate (equivalent to a handheld dedicated GPS).
GPS has known limitations in canyons (natural or urban) and heavy tree cover.