Compass calibration - Indoors?

KenMc · Jan 6, 2018

I've upgraded my Solo to 3.0.0 and need to calibrate my compass - but as I write this the outdoor temp is -12 F.

I don't understand what's going on in the calibration process - so what I'm doing may be absolutely wrong.

I'm using the Ardupilot compass calibration technique shown in this video (less the props):

I bought a $3 swivel chair (Goodwill), took off the seat and made a wood platform about 18" above the steel base. I put this in the center of a corner room with a north facing window.

I used this same platform and room to calibrate a Pixhawk 2.1 with Mission Planner - and it worked there.

In this case I used Solex - it seemed to work.

Is there a way to confirm the results (it will be a while before I can Fly)?

Am I just completely nuts for trying this?

Thank you for the incredible effort!

KenMc

PS - I NEVER attach my props indoors.

allen_993 · Jan 6, 2018

My compass calibration has never worked indoors...but works fine outdoors. Also, rotating the Solo in a single plane won't get it. You must rotate it top over bottom, side over side, all angles.

KenMc · Jan 6, 2018

I rotate it on all 6 axes. That's what makes a swivel base handy. You place the drone and rotate the base.

Wetstone · Jan 6, 2018

What we all need during calibration is an unaffected magnetic field from the Earth. Get away from metal and electrical objects as far as possible. Even if it appears to work, how will your home have affected the Earth's magnetic field? Do you want to take a chance that your solo will fly home correctly? I do not.

KenMc · Jan 6, 2018

So the fact that it appears to succeed is not reliable.

FWIW - I used a needle compass to survey the area where the swivel was placed, then I put the compass on top of the platform and rotated it - there didn't appear to be an impact. Away from the platform there were areas closer to the computer where there were detectable variations.

I agree with you completely - I want as close to a perfect calibration as possible - there's enough things to trouble shoot without adding another which could have been completely avoided.

Still - I wonder if there is any way to determine whether the calibration is correct? Can logs be turned on and the calibration results reviewed?

XevetS · Jan 6, 2018

Open up mission planner (windows program) and connect to the solo see for yourself what the mag is doing in relation to the solo's position..EKF, gps etc..

IronRanger · Jan 25, 2018

I’ve calibrated my compass in doors exclusively when I fly at my home for the past two years with no problem. You must calibrate all axises for proper calibration. I upgraded my compass from ver 1 to the mRo M8N a few months ago and now I get 18 to 21 sats consistantly with a DHOP of .5 to .8 every time. ROCK solid and very stabile in all modes.
I have flown several long range missions up to 1.2 miles never an issue, except last flight where I had a battery deplete from 45% to 10% in less than a minute and when RTH kicked in I didn’t think it would make it, but to my delight it landed 9 inches from where it took off. I never figured out the battery discharge issue and have retired it to my bench.

Pedals2Paddles · Jan 25, 2018

Think about the compass calibration is doing. It is designed to teach the compass how the earth's magnetic field looks taking into account the sources of magnetic interference on board the copter. If you do this magnetic calibration indoors surrounded by other sources of magnetic interference, you cannot and will not have a useful calibration. It will be saving offsets with artificially high or low values due to all the other sources of magnetic interference in your house. Wiring, furniture, electronic equipment, appliances, structural framework, etc etc.

This is why the instructions explicity state the compass calibration "must be done outdoors" and "Must be done in an open area away from buildings, vehicles, reinforced concrete slabs, power lines, MRI machines, metal fencing, etc."

Put on a coat, or wait for it to warm up!

IronRanger said:
I’ve calibrated my compass in doors exclusively when I fly at my home for the past two years with no problem. You must calibrate all axises for proper calibration. I upgraded my compass from ver 1 to the mRo M8N a few months ago and now I get 18 to 21 sats consistantly with a DHOP of .5 to .8 every time. ROCK solid and very stabile in all modes.
I have flown several long range missions up to 1.2 miles never an issue, except last flight where I had a battery deplete from 45% to 10% in less than a minute and when RTH kicked in I didn’t think it would make it, but to my delight it landed 9 inches from where it took off. I never figured out the battery discharge issue and have retired it to my bench.

You're talking about like 3 different things here. The GPS has nothing to do with the compass. Neither does the battery. Being lucky doing the compass calibration indoors does not make it proper.

IronRanger · Jan 25, 2018

Well then it must be a miracle, I stand here beside myself as you stated somewhere before. I guess I’ve just been lucky for 2 plus years. Great I’ll take that!

IronRanger · Jan 25, 2018

That’s not a dig, your explanation makes perfect sense.

allen_993 · Jan 25, 2018

My compass calibration is sensitive as hell. I go outside...with steel watch on...and it will NOT calibrate. Take steel watch off...calibrates every time. This is repeatable at will.

In the world of technology...luck can be one of your worst enemies. It will mask improper procedures...and then stop masking them at just the wrong moment

cynfab · Jan 25, 2018

I calibrate my level & compass indoors all the time.
I insure that I have removed my keys from my pockets.
I insure that I remove my other stuff which might be magnetic from my other pockets. Check your belt buckle too.
I insure that I don't have my phone anywhere nearby.
There are several places in my house that I can calibrate. There are many more that I cannot.

I calibrate my compass (and do a level cal) indoors so that I can do more software work with the Solo. When updating the firmware it always wants to do a compass cal.

Doing a compass cal indoors IS NO SUBSTITUTE for doing one outside. Just because it completes indoors doesn't mean it is "good".
Just because you have done it indoors and it flys OK outside doesn't mean that the indoor cal is "good".
Since NO ONE looks at the actual cal data and correction info (possibly exceping Matt, Randy and some other devs) no one has a clue as to what magnetic anomalies the cal is correcting for or their magnitude.
I have flown successfuly after only an indoor cal, so have lots of others. That doesn't make it the right way to fly a Solo.

(/Rant)

CAMXPOSURE · Jan 26, 2018

Where was the compass itself calibrated...

Pedals2Paddles · Jan 26, 2018

CAMXPOSURE said:
Where was the compass itself calibrated...

Who? When? Your question makes no sense.

IronRanger · Jan 26, 2018

cynfab said:
I calibrate my level & compass indoors all the time.
I insure that I have removed my keys from my pockets.
I insure that I remove my other stuff which might be magnetic from my other pockets. Check your belt buckle too.
I insure that I don't have my phone anywhere nearby.
There are several places in my house that I can calibrate. There are many more that I cannot.

I calibrate my compass (and do a level cal) indoors so that I can do more software work with the Solo. When updating the firmware it always wants to do a compass cal.

Doing a compass cal indoors IS NO SUBSTITUTE for doing one outside. Just because it completes indoors doesn't mean it is "good".
Just because you have done it indoors and it flys OK outside doesn't mean that the indoor cal is "good".
Since NO ONE looks at the actual cal data and correction info (possibly exceping Matt, Randy and some other devs) no one has a clue as to what magnetic anomalies the cal is correcting for or their magnitude.
I have flown successfuly after only an indoor cal, so have lots of others. That doesn't make it the right way to fly a Solo.

(/Rant)

After the explanation P2P gave, I did a lot of reading and quite frankly I had no idea just how sensitive they are. Thank goodness I only fly on my little 500 acre Ranch, checking fence lines and looking for cattle, last nite I went outside and did a compass calibration before I flew.

Joe Horn · Jan 26, 2018

IronRanger said:
Well then it must be a miracle, I stand here beside myself as you stated somewhere before. I guess I’ve just been lucky for 2 plus years. Great I’ll take that!

When NASA was warned 32 years ago tomorrow that the O-rings might fail in the cold weather, they replied, "Are you saying we've just been lucky for 5 years?"