When you power up your Phantom and it's getting ready to fly, the home point will be marked at your Phantom's current location (the takeoff point). After taking off, you can manually reset the home point from the top of the "Main Controller Settings" section of DJI GO. You'll see the option to set the home point to your Phantom's current location (this works on all devices) or to your mobile device's current location (if it has a GPS receiver).