The question is as simple and clear as it sounds.
When celullar data and Wi-Fi are turned off on my iPhone 6, location services work great and I get my location in a moment with a precision of 1-2 meters.
However, if I turn my celullar data on, it takes 10-15 seconds to get my location and, usually, it is pretty incorrect (+- 200 meters and it randomly moves around while I am standing at the same place). As some of my friends have the same problem, it looks like it is mobile network operator issue (Altel 4G, Kazakhstan).
Why does iPhone prefer to use cell network-based or wifi-based location services while GPS is doing good? How can I turn off cell network-based and wifi-based location services, so it uses only GPS services and doesn't work at all if GPS is not available.
Now, I have to turn my celullar data off in order to get my precise location and turn it on later. However, it makes playing some games involving both location services and celullar data impossible.