Being able to know your map location at every single moment is very important for long flights. There are many GPS systems in the market that help your controller and feed it your craft's coordinates. So, you can get your location as a mark on a map via telemetry and use the Mission Planner software or any other navigation software to place some navigation points and set your quadcopter to autopilot.
In the following image, we can see the NEO 6m GPS module. It can be easily mounted on the ArduPilot flight controller and it will feed your craft the required coordinates:
Note that the GPS also has drawbacks. Unfortunately, the GPS as a standalone system cannot get accurate coordinates. As a result, the flight controller uses a GPS module combined with an accelerometer, magnetometer, and maybe some more components. Each of them has small errors but the combination is very good. A GPS module should not be trusted under cloudy weather, in the rain, or inside...