[avidiax]

My understanding of it is that it's especially apparent when you are within 1 prop width of the ground. For a quadcopter, it's most apparent just off the ground, since the props are small compared to the entire craft. You don't usually operate the drone in ground effect for very long, but you need to really push the throttle to get in the air, and the drone floats if you are close to the ground.

The other effects are more apparent, especially settling with power, the tendency to pitch back as you go faster, and translational lift. Modeling all of these accurately turns into a fluid simulation, so probably you'd just want a heuristic.