elevation altitude of home reads incorrectly

[N017RW]

Correct, you won't find any mention of altitude during calibration.

HOWEVER...The IMU contains: a 3-axis accelerometer, a 3-axis angular velocity meter and a barometric altimeter.

Therefore it is not a stretch that during IMU calibration the barometer is zeroed in a similar fashion to the accel. and velocity sensors.

If so, this might contribute to the error you are experiencing.

Nope ...... unfortunately there's no calibration for the altimeter/barometric sensor.
I had one that read + to - 60 feet on the ground, and DJI California said to return itto mt dealer, as there is no calibration for it.
It either works properly and reads within a few feet, or it's gone Elvis.

Thanks.

How does it 'know' what it's altitude is then (within a few feet)?

 

[Flyer91]

It doesn't.
I suspect it may know it's alt with respect to the error at take off, becase it might just use that as it's zero refference, and then fly off the error's offset.

Mine would hold alt, but I never did try to RTH with it.

Since you seem to be indicating that RTH works fine, my guess is that it knows the 70' take off alt is it's "home alt" and it's flying off it just as if you were flying with a reset "home" alt ...... by doing the switch flip to reset home when already airborne. :?: :?: :?:

 

[N017RW]

Yea that was another poster actually reporting the error.

Ok I think I was being too literal.

It doesn't actually calibrate per se as that would require a reference, but it rather uses baro. pressure at take-off or home lock to establish GL and references pressure altitude from there.

Sure, that's what I would expect too.

 

[mtpisgah]

its just a numbers. phantom will all recalcs. you can use the starting elevation as a reference and differentiates if you want to know the real numbers (metric makes harder using iosd). i might be wrong. but, your phantom fly good now and thats all matters.

 

[Flyer91]

its just a numbers. phantom will all recalcs. you can use the starting elevation as a reference and differentiates if you want to know the real numbers (metric makes harder using iosd). i might be wrong. but, your phantom fly good now and thats all matters.

Only if you always fly in the land of flat.
If you want to use a terrain map to reset the home alt to a level above the highest ground level in your flight path, or an obstical of known height, you will always need to add/subtract the error offset.
That might be acceptable if the error/offset is consistent, but if it fluxuates (as mine did) you can't use the altimeter for the purpose you paid to have it for.