Does headless mode and one key return need GPS chip in drone?

I'm looking at drones, and a lot of them have different variantd with and without GPS.However, they also advertise those 2 features, but don't say whether you need the GPS variant for them or not, so I don't know which variant (with GPS or not) to buy.Can you help?How does headless mode work? Does it need GPS to know where you are so that it changes its directions relative to you?How does one key return work? Does it need GPS to know where it was and return to it? via /r/drones https://ift.tt/2YAUbyp