When flying my Phantom 3 it does not hover well. It will generally maintain altitude but moves left and right for long distances. I recalibrate the compass
every time I fly. Thanks

Hi. I'm sorry for the inconvenience and trouble caused. I would like to clarify, may I know if the firmware of your drone is updated? Also, can you please try to calibrate your IMU? For reference, you may watch the video tutorial below. If you have other concern, please let us know. Thank you.

You should never have to calibrate the compass.  Do as Natalia suggested and see if it helps.   A little drift is normal.

DJI Natalia Posted at 2018-8-6 08:10
Hi. I'm sorry for the inconvenience and trouble caused. I would like to clarify, may I know if the firmware of your drone is updated? Also, can you please try to calibrate your IMU? For reference, you may watch the video tutorial below. If you have other concern, please let us know. Thank you.

https://www.youtube.com/watch?v=4WGZUl5n1fA

Thanks for the reply. I did the IMU calibration again and that fixed my problem. How do I know
when the IMU needs  recalibrated? I didn't notice an alarm for this. I often get an alarm for
compass recalibration. Thanks again>

Boatnut Posted at 2018-8-6 08:50
Thanks for the reply. I did the IMU calibration again and that fixed my problem. How do I know
when the IMU needs  recalibrated? I didn't notice an alarm for this. I often get an alarm for
compass recalibration. Thanks again>

Awesome! That's good to know that it's now working. Actually, you will only get the notification once a message pop-up to your screen saying that you need to calibrate your IMU. I suggest you calibrate your IMU everytime you fly your drone for safe flight and to avoid any other issue. Thank you.