Android App distance readings incorrect?

[madcrosoft_uk]

Phantom 2 Vision running the android app The distance seem to be hit and miss? any body know if this is common or there may be a quick fix?
Do I need GPS switched on the phone?
I would rather get some info before venturing past 100m away.
PS flies great, GPS lock all ace and calibration is good
Thanks in advance

 

[madcrosoft_uk]

It seems from the negative response that nobody else has this problem and cannot provide help? should I contact DJI to see if I can get some feedback?