Hi. Is it necessary to calibrate the compass before each flight  ?
Some times my screen says  home point not recognized .   
Still trying to learn.  Old dog new trick thing.   

The recommendation now is to get a good calibration in an open area away from ferrous materials and strong electric fields (i.e. Rebar in concrete, cars, steel framed structures, power lines & power stations, underground pipes etc). Once you have that calibration then the general consensus is that it does not need to be done again unless prompted by the system, or if you have moved a great distance (once again at least a couple of hundred miles is the general opinion).

The problem with calibrating at each session is that there is more likelihood of getting a bad calibration. In which case the aircraft may report errors where there aren't any, and in a worst case fly off on its own in an ever increasing spiral.

Earlier model (Up to P4 ?) manuals stated that it needed to be done frequently, and DJI have been slow to rectify this, which I believe they have done for the latest model manuals.

'Home point' is set by the GPS/GLONASS satellite navigation receivers, and usually ten or more satellites needed to set home position of aircraft.

No ... it's not necessary or recommended.
Check p51 of the P4 manual to see what DJI recommends:  https://dl.djicdn.com/downloads/ ... ser+Manual+v1.4.pdf

We were told to re-calibrate if moving more than about 50km from last calibration point.

This is from the P4 manual

Yes,they are highly recommend,it will decrease your chances of losing your drone,compass is an important need when your drone is lost connection and using GPS to navigate home.  

Jerryjin Posted at 2017-5-1 16:29
Yes,they are highly recommend,it will decrease your chances of losing your drone,compass is an important need when your drone is lost connection and using GPS to navigate home.

Wrong, from the P4 Pro manual:-

Labroides Posted at 2017-5-1 14:40
No ... it's not necessary or recommended.
Check p51 of the P4 manual to see what DJI recommends:  https://dl.djicdn.com/downloads/phantom_4/20170327/Phantom+4+User+Manual+v1.4.pdf

The problem with the P4 manual is that Page 52 then contradicts page 51, see extract of P52:-

Jerryjin Posted at 2017-5-1 16:29
Yes,they are highly recommend,it will decrease your chances of losing your drone,compass is an important need when your drone is lost connection and using GPS to navigate home.

Despite poor wording in old DJI manuals and the popular misconception this has created, it is safer to get one good compass calibration and just leave it.
Way too many lost phantom stories start with :  I calibrated the compass as I always do ....
Giving your phantom a bad calibration is a good way to have serious flight problems.
The compass doesn't lose its calibration.

Labroides Posted at 2017-5-1 14:40
No ... it's not necessary or recommended.
Check p51 of the P4 manual to see what DJI recommends:  https://dl.djicdn.com/downloads/phantom_4/20170327/Phantom+4+User+Manual+v1.4.pdf

Thank you   Understood

Aardvark Posted at 2017-5-1 16:55
The problem with the P4 manual is that Page 52 then contradicts page 51, see extract of P52:-

Thanks   There we're 2 very informative replies to my question   One simple and to the point .
And one that helped me understand even more about the calibration process  
Many Thanks to all

Not required as said by many above, and to prove the point, i had a decent calibration (in the shores of Lake baikal in Russia, no metal, no interference), then flew it in Mongolia approx 1300kms away, then flew it in China 1500kms away.....
All with the initial calibration and it worked like a charm.

Labroides Posted at 2017-5-1 17:38
Despite poor wording in old DJI manuals and the popular misconception this has created, it is safer to get one good compass calibration and just leave it.
Way too many lost phantom stories start with :  I calibrated the compass as I always do ....
Giving your phantom a bad calibration is a good way to have serious flight problems.

Thanks that is good advise understood.     Many thanks

visitkans Posted at 2017-5-4 07:40
Not required as said by many above, and to prove the point, i had a decent calibration (in the shores of Lake baikal in Russia, no metal, no interference), then flew it in Mongolia approx 1300kms away, then flew it in China 1500kms away.....
All with the initial calibration and it worked like a charm.

Yup I understand.  But still scary flying.  I am still learning.  

fansc62380a9 Posted at 2017-5-5 07:34
Yup I understand.  But still scary flying.  I am still learning.

hahha. I too was..

and i read a big detailed post on the phantom pilots on why frequent calibs might introduce more errors than a good one and i stopped then but it still scares me thou....