Altitude variation in flight mission

Dear Members,

I have a new build and the Drone flies perfectly fine in manual (stabilize, loiter) mode.

In order to test it for a mission, I created a layout/kml and made a survey grid on the mission planner. The altitude was relative (Normal straight field, no terrain area) and set at 10 meters (No obstacles around). During the flight, Auto takeoff and then went to waypoint 1 and started the survey. The observation was once it started moving forward, the altitude decreased to a certain extent. Reached waypoint 2, and stopped beyond the given grid limit. Increased the altitude to 10 meters and started moving forward. The same pattern followed. Altitude variation was low - 7 meters and high - 11 meters.
2nd thing I did not like is the flying speed which went to around 11 m/s whereas the given flying speed in the survey grid option was 5 or 6 m/s.

I am curious to understand the issue and resolve the following: -

  1. Altitude decrease while in auto mission
  2. Decrease or limit the speed.
  3. Braking at the exact location. (reduce/eliminate overshoot)

Drone details - quadcopter, arducopter 4.2.1 mostly and the latest mission planner.

Requesting your support and help.

Thank You.

Like I just explained in another thread, do wind estimation calibration, and/or use a RTK GNSS.

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Dear Amilcarlucas,

Thank you for your input.
I would like to request you to share the link of your previous thread response to go through.

Probably you mentioned about this - Windspeed Estimation and Baro Compensation — Copter documentation. but not sure.

If that is happening because of the flight controller mounted in open (wind accessible) location, covering it up and making it a closed area can resolve this issue?

Also, will the same issue happen while flying manually? I tried to check manually and there too it was decreasing the altitude a little as well as a little delayed braking. Is the reason same for this?

Thank you again

That is the documentation I was talking about.

yes affects other flight modes as well.

Yes covering it will maybe improve it.

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Hi again,

I have done the Wind Estimation calibration as per the given points on the aforementioned link. However, I do not see any changes in the EKF3 drag coefficient (final) value, in the configurations (automatically).

Also, in AltHold mode, it keeps on drifting so we have to adjust the drone a little to stop moving behind the pilot’s flying location.

Three, We are not getting a clear idea about how to identify the value in the logs. Can you please help us with the same?

Also, I would like to inform you that before going for Windspeed Estimation, I did a small auto mission. The altitude variation graph image is attached with this. Is this much altitude variation common?

Thanks again

AltHold will drift, it only holds altitude.
Check you dont have any trims set on your transmitter and check in the Radio Calibration screen, ensure all controls show as centred - redo calbration if necessary.
Then do the “Calibrate Level” in Mission Planner.
Do NOT assume the aircraft is level because of the surface it is sitting on, you need to use a spirit level to test that across the tops of motors is level - build up under the landing gear to correctly level the whole aircraft before pressing the “Calibrate Level” button.

Thank you Shawn.
I will recheck that and do it as guided by you + ardupilot document.

Many thanks for the input.