Anyone else notice that the Iris moves in Loiter mode?

There was a bit of wind. However I was surprised that the Iris would drift back and to the right consistently. I played with the controller but it seemed that the trim is very finicky. I’ll do some more reading but if anyone has some thoughts…


For what it’s worth, I’ve noticed that for the first few minutes after getting a GPS lock, you really need to keep an eye on things if you switch to a mode requiring GPS (Loiter, PosHold, etc) until things settle down. It will drift around and occasionally take off for parts unknown until I reel it in by switching to Stabilize or Alt Hold. It happens most in my back yard where there are trees and a house nearby. It’s much less of a problem in wide-open areas.

Hi guys,

Logs would help.

Are you monitoring your GPS HDOP (horizontal dilution of precision)? This can certainly lead to some drifting. You can see HDOP “live” in Mission Planner, or look at in the logs. Also, you can see the delta in XY position in the logs.

@kellyschrock - you are likely seeing the effects of GPS multipath interference, where GPS signals bounce off the large objects to be received by your antenna with a tiny time delay, causing position errors.

@kcorkum don’t apply any trims on your TX, the autopilot will keep feeding them in.

@Bill I’m certain that’s what it is. The very first time I flew my Iris the day I got it, I switched to Loiter and watched in horror as it took off on its own and flew between two trees. I managed to land it in the middle of the street. I mentioned something on the Iris developer group forum and someone (Craig Elder I think) said there’s a problem with multipathing. A year+ later, I’m used to it. It’s kind of amusing watching it fly perfectly stable above the house or well away from it, and then start getting all weird when it gets close to things it can actually run into. I’ve observed my Phantom doing the same thing.

after watching it for a couple of weeks, I’m definitely seeing that the Loiter is more effective after a couple of minutes. I’ve been flying it in 10mph winds and the loiter is working awesomely!