Re: Gps Help
« Reply #15 on: August 19, 2017, 05:40:42 pm »
I have someone else push the "save position" button so that I do not have to set the quad down.
Because it is a continuous operation, could I just start the calibration and spin the quad in every direction (like with ArduCopter) and then skip through the rest of the calibration?
« Last Edit: August 19, 2017, 06:18:05 pm by Fireflyer »


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Re: Gps Help
« Reply #16 on: August 19, 2017, 06:27:22 pm »
The answer is yes, just cover all the 3D space in "blind mode" while rotating the quad in all directions.
Search for "arducopter dance" in Youtube.
Just skip the 5 steps at start and keep last step for calibration before saving.

Re: Gps Help
« Reply #17 on: August 19, 2017, 06:47:36 pm »

What about vibration damping and PositionHold Settings Bank (see reply 12)?

Re: Gps Help
« Reply #18 on: August 20, 2017, 07:06:27 am »
I have had quads where a vibration damping FC mount helped and some where it actually hurt and flew better after removing it.

You can adjust GPS flight mode PIDs in VtolPathFollowerSettings.

Normal PIDs in Stabilization page should be as good as possible and not changed from there for any reason.  You can change rotation rates there.

Re: Gps Help
« Reply #19 on: August 20, 2017, 04:55:44 pm »
I will try to get PositionHold working before tuning it a bit better.

Just wondering, if GPS only has 2-3m accuracy, how can the FC keep a quad from straying more than 1m in PositionHold (like a DJI phantom)?

Also, is there a preferred method of calibrating the mag? That is, should I just do it the normal way or should I do what f5soh suggested?

Re: Gps Help
« Reply #20 on: August 20, 2017, 05:20:21 pm »
I do it the way f5soh said, but whatever is easiest to do correctly.  Easiest may be to follow directions exactly.

Re: Gps Help
« Reply #21 on: August 20, 2017, 06:08:40 pm »
How does PositionHold keep a quad in one place without straying more than half a meter? I thought GPS only had 2-3m accuracy, but I have seen DJI phantoms and such do it.

Re: Gps Help
« Reply #22 on: August 20, 2017, 08:37:39 pm »
Any brand of FC firmware that does GPS PH can hold very accurate PH for a short time (minutes), but the GPS itself drifts.  On the GCS, watch the GPS wander over the course of an hour when the quad is on the ground in one place.  DJI GPS unit filters it's coordinates for less drift, but it also doesn't respond as quickly as raw GPS coordinates.  By my testing with stock settings for all, DJI NAZA-M FC probably holds a smoother PH in zero wind, but LibrePilot FC can be flown at higher speeds; also in high turbulent wind that would ground a DJI.

The main issue is that over longer time periods, GPS is less accurate than over short time periods.  That is why it is best to capture a home / base location with each battery.  That is why with advanced firmwares (such as LibrePilot) that allow you to store waypoints in a flight plan for use another day, the corridor the waypoint flight flies in must be at least 6 meters wide (2+ meter horizontal deviation) and at least 4 meters off the ground (3+ meter vertical deviation).  These are my own trial and error deviations that I found work.

Vertical PH is greatly helped by the use of a barometer that is accurate to 4cm (all GPS capable FC firmwares and hardwares), but baro altitude of one day doesn't work the next day when a storm front approaches and the local barometer has changed a lot.
« Last Edit: August 21, 2017, 06:24:26 am by TheOtherCliff »