Get a level and a compass

CraigCam · Jan 20, 2017

Hey everybody,
The latest firmware thread has covered a lot of territory and of course compass calibration. In a few placed there have been discussions of different flipping methods. I believe a missing part of the instructions that really help is the fundamental of starting out level and facing north when you initialize the H. I've attached a few photos of a recent prep. And no, the magnet on the level is not a problem as it's less magnetic than your motors. I have it now where I advance the arms CCW after usually one slow roll as the slower you roll, the better it gathers data. Taking my time to prep my launch and check everything in the air in front of me for a minute or so has eliminated drift and odd behaviors. I've also had the left stick not working right thing but persistent ST calibration gets it behaving. My efforts have been rewarded with some great shots of our desert washes running with winter snow runoff as I have trust in my H once I finish my prep. Hope these pics help.

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Guest22 · Jan 20, 2017

Thank you for sharing your thoughts. I have always had my "H" facing North during initialization/take-off. I do know that my take-off/land platform (portable table) is not level at the house. It's off a few degrees.

I have had all successful flights (stable hover, controls operate correctly, and no odd behavior) using my take-off procedures, so I think you are onto something.

PatR · Jan 20, 2017

If your living room/kitchen floor is flat, it's close enough for the accelerometer calibration, unless you are climbing up and downhill whenever you cross the room.

ArnhemAnt · Jan 21, 2017

Nice work with the painted shell. Looks great. I almost thought you had the 520!!

CraigCam · Jan 21, 2017

It really helps see that bugger...

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ArnhemAnt · Jan 21, 2017

CraigCam said:
It really helps see that bugger...

Yeah. I'm really surprised that no-one has started making and selling the covers for the H in different colours. I'd certainly be interested in one if the price was right.

JulesTEO · Jan 21, 2017

I'm sorry if I have posted this video a few times already on the forum, but I still have to disagree that a level and a compass is a "must have" to have the H behaving as it should.

Greetings!

ArnhemAnt · Jan 21, 2017

There are definitely some variances in regards to how people do their calibrations - compass, accelerometer and gimbal. Whether you are on level ground or not should have no effect on the compass calibration. For the accelerometer, the IDEAL is to be on a level surface, or at least, as level as possible. What is more important is that the airframe is not susceptible to any movement or vibrations during this stage. This is also important on each and every start up as the accelerometers will 'initialise' (can't think of a better term right now).
Again, camera gimbal calibration should be on as level as possible of a surface, otherwise your horizon, etc may be tilted in videos and photos.

It would be interesting to see what would happen if you did the accelerometer calibration on something like a 45 degree angle. My guess is that you will see some drifting while in flight.

To summarise, if you want to ensure you have ruled out all possible issues, use a level, etc, for the accelerometer and gimbal calibration (and ensure the airframe is dead still) and when doing the compass calibration, stay well away from any possible magnetic interference.

Chilcotin · Jan 21, 2017

If you really need to calibrate accellerometer, keep it still and as close to level as reasonable. There is also no requirement to have it pointing north at beginning of compass cal. These ones don't work that way.
Try it pointing south, you will see it works fine.
The trick is to do it away from potential interference.

CraigCam · Jan 21, 2017

Chilcotin said:
If you really need to calibrate accellerometer, keep it still and as close to level as reasonable. There is also no requirement to have it pointing north at beginning of compass cal. These ones don't work that way.
Try it pointing south, you will see it works fine.
The trick is to do it away from potential interference.

All I know is pointing north has stopped compass drops in flight. And level starts are good for gyros. It could be my own mythology but considering many of the internal components look eerily similar to parts from my blade quads, I'm erring on the side of what has always worked. What we can't tell is how high a percentage of directional data is collected and what's considered enough.
What I have seen is quick and careless compass calibrate while accepted be the IMU does not guarantee total stability. Since I got back to paying attention to my location, my compass calibrations go smoothly and hold better. It could be all psychological but it helps me fly more focused by taking my time and being more methodical.

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PatR · Jan 21, 2017

People like to debate the need to aim a multirotor north at the start of a compass calibration. It's not worth covering it over and over again. Do what you want but recognize those that start out facing north generally have fewer course alignment issues when flying. It's just not that hard to understand where the sun rises and sets to have the H facing the mid point between where sun rises on the right and sun sets on the left.

K3CFPV · Jan 21, 2017

I've read that when doing the compass calibration, one should do it without the CGO3+ attached to minimize interference. However, this seems a bit counter-intuitive to me as it's flown with the camera and one would think it should be calibrated the same way it is flown. Not having a cell phone in your pocket is always a good idea (no cellular, wifi or bluetooth interference). Thoughts on the CGO3+?

ArnhemAnt · Jan 21, 2017

I have always removed the gimbal when doing the compass calibration, not so much for the potential interference, but more because I am sure those gimbal motors don't like being spun around like that.