ianwood said:
Exactly. 1 red, 1 green is 5 satellites. That's not enough for a good level of precision. You should expect the P2 to drift and you should also expect it to move on it's own if and when it picks up more satellites and moves to the position it thinks it should be in.
A couple of quick points.
For blinks, one red, one green, in NAZA-M mode, should indicate 6 satellites found, not five. Six is the bare minimum needed to fly in GPS mode, and if it drops below this, you are in ATTI. Seven or more satellites found is green-only blinks.
With respect to drifting, there is more than just the satellites at play. the Naza used to have a ~2 minute warm-up period, which allows the IMU to warm up and stabilize. After a lot of complaining from people about how it took too long to get in the air, DJI shortened and then eliminated the warm-up, so now you can take off very quickly, but the warm-up happens in the air. What this means is that for the first few minutes of flight, you may have a bit more drifting in GPS (or ATTI for that matter) mode until the IMU settles.
The timing sometimes corresponds with number of satellites locked, so people tend to think GPS is the sole cause. This gets reinforced in multi-battery flights as the GPS can lock on much quicker on subsequent boots after the first power-up, so people see the satellite number jump up to 7-9 quickly on their second flight and note there's no drifting. The main cause though is that the IMU has already warmed to operating temperature from the previous flight.