Recently, my Phantom 2V+ is very slow to get GPS signal locked. As compare to my friend's 2V+, he can get GPS locked in about 10s but for me it takes ages, sometimes over 3 minutes. So I hooked up my 2V+ to Assistant Software to see if there is wrong doing in setting.
I am in NAZA mode of course, when I checked on the Advanced setting of IOC, I found that IOC was disable, but I am sure it was enable before. Anyway, I ticked the box to enable IOC, so suppose when I toggle S2 in the transmitter, a blue highligh of Home Lock, Course Lock or OFF should be displayed, but it wasn't, when I left the IOC page and backed again, IOC was still disable!
I soon found out that there was a small dialogue box shown in my computer screen saying that GPS is not calibrated [Error 27], can someone tell me what's wrong with my 2V+? How do I calibrate the GPS? I checked all the settings and couldn't find any calibration button for GPS, please help!

Stanley

ERROR [27]
GPS not calibrated, or magnetic field interference. Please calibrate GPS again in good condition. Please contact your dealer for all technical support questions.

I know this does not really help, but this is from the Phantom FAQ page.
I guess you start with an advanced IMU calibration and then do a compass calibration and see what happens, although I would have thought neither would have any effect on the GPS module ?