S-GPS isn't the ability to find satellites and use GPS without a data connection. Every standalone GPS chip can do that (it's how the technology was designed to work by the military and how Garmins and Tom-Toms have operated for years). S-GPS (Simultaneous GPS) is the ability to receive both GPS and cellular signals at the same time. For most devices that aren't S-GPS capable, the cellular reception and GPS reception alternate back and forth, with both not actually running at the same time because they share the same RF radio. With S-GPS, they can both run at the same time, allowing the phone to pull data from the cellular network as well as from the GPS signal in order to get faster and more accurate GPS locks. It's similar to A-GPS, except faster and more accurate.
But regardless of whether one has a device that is S-GPS capable or just A-GPS capable, the standalone GPS will still function and track your route without a data connection if you have an app with offline maps. S-GPS will just help you get a faster, and more accurate GPS lock when you have a cellular data connection. In and of itself, S-GPS capabilities don't help to establish a lock any faster than A-GPS capabilities when there is no network connection.
