GPS signal works independently of data connection - i.e. your phone does not need a data connection to be able to tell you your current lat,long. A GPS module is a pure receiver, and does not require an outgoing connection to run. Using an internet connection can help to get your location faster, but it is not needed.
So an offline device can still receive lat,long coordinates, and our software (all being offline) can take the lat,long coordinates and do the conversion.
This works for current location.