Quadcopter suddenly moved after about 6 minutes on poshold, this happened a few times on poshold mode. Look like not GPS glitch.
OK? Without logs not much the community can help you with I think.
2016-12-07 17-34-00.zip (3.8 MB)
Please find the logs for reference. Thanks.
Looks like GPS Doppler effect due to trees and buildings in the surrounding area. Looks like GPS went North so the copter probably went south towards the building to compensate for the drift in GPS position.
In fact, the quadcopter faced north and it suddenly went to the west. This always happened when I changed mode from Alt-hold to poshold for a period of time but loiter did not have this problem.
After I reset the pixhawk, problem was solved.