Correcting a 'wobbly' path between Waypoints?

John are you seeing the other replies we have sent you?

Thanks, Grant.

Hi Grant,
Yes, thank you.
Like I said in my other post, I have had to replace the motor and have only just got that up and running so I am back on track.
Thank you

Here is the actual path (green) logged by the GPS when NAV1_PERIOD is set to default 20 -

1 - the path width is 20 meters wide
2 - the turns are gentle and are very close / accurate to path border


With a real boat AutoPilot we have three primary settings and are very quick and easy to set:-
Navigation Settings for AutoPilot
1 - Arrival Radius - what radius is considered "waypoint reached"
2 - XTE Limit - path width
3 - Steering Response - 1 for high speed (delayed gentle corrections), 2 for low speed (erratic quick corrections)

How do we do these three settings on the Pixhawk?

Lets forget about the P and I term at the moment. They both may be a bit low but lets not take that into account. You have the drunken sailor path of not holding a steady course yet the boat seems to be able to turn fairly quick to start moving in the other direction to correct. Try dropping your NAV1_ PERIOD to 15 and see what happens. It looks like about every 60 meters it repeats the same path. Whats the boat speed?

David R. Boulanger

@John lets keep the discussion regarding this topic just in this thread so all the info is together.
David’s suggestion is a good one - give that a whirl.
If you could attach a dataflash log of the wobbly run (assuming you had LOG_BITMASK set appropriately) I can have a look.
Thanks, Grant.

The speed of the boat is 22kph at max throttle …

Where would I find the dataflash, and how would I set the LOG_BITMASK?

These settings look very good -


Today I spent the morning concentrating on NAVL1_PERIOD only and this is what I came up with:-

The path is very symmetrical and is your typical sine wave pattern. A is the path width and B is ‘wobble’ length.

Default 20:
A = 80ft
B = 185ft

A = 245ft
B = 400ft

A = 55ft
B = 120ft

A = 35ft
B = 95ft

Question - How do I get the path width of ‘1’ and the wobble length of ‘30’?

Here are the actual trails from Google Earth …

Have you tried using more STEER2SRV P and I?
David R. Boulanger

Log information
Fastest way is to pull the SD card from the pixhawk and copy the logs off. Note I only want 1 log of when the issue occurred. Don’t post all of the as I won’t know which to analyse. And you will need to upload it to dropbox or google drive or whatever you use and post a link here.

Thanks, Grant.

Why do I only have this problem now after I did the firmware update?

Is this not possibly the ‘elephant in the room’?

You using 3.0.1 or the new Beta. When I upgraded from 3.0 to 3.0.1 I only had a very minor adjustment to make. The sea state your operating in and the characteristics of your boat are extremely different than mine however. Give Grant a log as he is very skilled in this stuff.

David R. Boulanger

Hi Grant,
Here are one of the logs from Monday’s missions -


Where would I find the firmware version on the Pixhawk?

Thanks for the vote of confidence David :slight_smile: I do my best.

Hi John. If you look at the console tab in mission planner that will tell you what the firmware version number is when the pixhawk boots/reboots.

The dataflash log you attached as some odd parameter settings in it. You have
This should be much higher for your boat. Its almost certainly causing the weaving. Try 10 and go from there. Also note
which means you are only checking RC and GPS lock at startup. Is there a reason you have changed it to check only these 2 rather then all of them? I know that’s the example given of how to set the ARMING_CHECK values but you should really check them all by setting it to 1.

Let us know how you go.

Thanks, Grant.

Hi Grant,

Ok, I will check.

Yes, NAVL1_PERIOD was one of the settings but as you can see it simply makes the ‘path’ narrower, but in no way stops the ‘wobbly’ trail, as seen here … (red trail)

I was having arming issues and the is why I changed it to 72, but I sorted those issues out and now have it on 1, but the ‘wobbly’ trail is still exactly the same.

Today I intend to play with P and I parameters.

Thank you for all your help, I would be totally lost without your help.


For some reason I could not view anything on the log that was sent. I could not graph anything. problem on my end I guess. With my boat I have noticed that my I is 1/10 of my P and then I tweak the NAVL1 to smooth thing out. The way I have tuned was to play with P and I to the point that the boat goes in a very straight line but weaves back and forth really fast. Then try a little less I and NAVL1 a little higher till things smooth out. Every boat will be different. I still also look at the sea state that you run in. I usually run in fairly calm water and when I don’t my rudders work harder than I really want them to but the boat maintains course.

David R. Boulanger