Earlier quoted context omitted.
GPS can be turned off.
GPS based on solely on satellite signals tends to require several to tens of minutes before it can provide an accurate location. Cell phone geolocation tends to much much faster because it utilizes terrestrial radio signals from cell towers and wifi networks and who knows what else...a database of such signals is part of the what else.
Though it requires an internet connection an online database to actually compute the location. So, probably not as useful for a camera.
skyhookwireless.com is one example of a wifi location database.