I did a small test mission last weekend and found the GPS navigation accuracy was quite poor. I've attached a screenshot showing the actual path taken compared to the WP path it should have followed from WPs 2 to 9. The speed was set to 5 or 6 m/s.
I flew the same mission 3 or 4 times and it was just as bad for each flight.
The WP circles shown are 3m radius to give you a sense of the scale. I had 9 or 10 satellites the whole time. I was in a very shallow valley, I didn't expect any GPS degradation because of the location.
Any ideas what the problem might be? Or where I should start looking? There don't seem to be any navigation tuning parameters for Arducopter like there are for fixed wings.
(It may or may not be related that my photos were quite bad too. They weren't very sharp. I used a shutter speed of 1/1000 which I thought would be fast enough to overcome any vibration issues. I didn't get ANY really good sharp images so I think it was probably a focus issue. But I haven't checked the vibration for a while so that is something I'll check again.)
Log file attached.