Hi All,

Went out this morning and flying around beach area and across water.  Launched off elevated position and flew over small drop off of about 5-8 metres.  Fly along beach and over water etc for some time.  This was often below where I was standiing.  When returning to Phantom 4 to the launch position I checked the altitude on the Go App and it was showing 10 metres but the Phantom 4 was still below my standing position which of course didnt make any sense.  I took it up to provide sufficient clearance to return to the home point and safely landed but the App was still showing 17 metres.   All ended well in this instance but bit concerned about the accurancy of the Altitute reading as I feel it is important when flying in areas where the elevation changes.  I did a calibration before I started flying but I did move a short distance (200metres) between flights and didnt recalibrate as it didnt ask me to.  Should I have?  Anyway, I will be very vigilant next time I am out but was hoping someone could shed some light of preventing this behaviour in the future.

Regards
Greg

Hello Greg, what calibration you did? IMU calibration?
Have you done the VPS calibration before?
Also the altitude is measured by the barometer, and it isn't always accurate. It will be affected by airflow and environment.

Hi Mindy, I only did a compass calibration.  I haven't done an IMU or VPS calibration before.  Should I?  Is this something I should do regularly.  Sorry, new to all this, only had the Phantom 4 for about a month.  First time I have noticed this behaviour.  

DJI Mindy Posted at 2016-11-7 22:25
Hello Greg, what calibration you did? IMU calibration?
Have you done the VPS calibration before?
Also the altitude is measured by the barometer, and it isn't always accurate. It will be affected by airflow and environment.

As a simple fix to this problem and a handy added feature perhaps there could be an option in GO/GO4 to reset the Altitude to match the Ultrasonic Altitude reading when the Aircraft is below 10m in much the same way it is possible to reset the home point of the Aircraft mid flight.

I get the same issue, I did have issues calibrating my vps and collision avoidance sensors and have just been too lazy to recalibrate them, but Id assume a calibration for both imu and positioning system wouldn't hurt.