Bad GPS navigation

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.

2014-07-05 12-25-27.tlog.jpg

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  • 300km

    SOLVED! My roll and pitch P settings were just too docile.

    I flew new circuit at a new location and it was just as bad, then I increased the P settings from 0.08 in several steps up to 0.11 and got a big improvement. (Ignore the wander around WP6, I switched to stabilise mode while I changed the settings)3701794143?profile=originalOne last question though. Is there any way to get it to fly closer to the corners instead of turning a bit earlier. It turns a little too early in my view, especially at WP3.

    • That's good news.

      In Flight Planner, change WP radius to a lower number, just don't make it too small. You can also have it stop and delay at each WP (in box to the right of WP). I like to have the nose oriented toward each new WP as well, then at the RTL it turns to its original orientation on takeoff.

      There are many parameters that can be set to your liking. Be careful though; one wrong decimal place or number and the copter could seeing 0 alt real fast.

      Have you done Auto Tune? I did it twice to get it right. Just make sure the wind is very still. No expert at MP, but getting better :)

  • It might be possible that your magnetometer is pointing the wrong way? I'm not sure what might happen on an auto flight if that is the case.

  • 300km

    The HDOP was about 1.8m on average. I had 11 sats for 98% of the time (a few seconds down to 10 or 9). All very good so I was wondering if there are any navigation settings I need to tune.

    It was Saturday the 12th of July (from memory) and I'm in New Zealand.

  • when was this and where you?

    I had a issue the other night on a quad I felt had solved the loiter hold problem a few weeks ago, then it seemed back, however noticed that my gps on my phone was also not very sensitive either at that point. 

    it was close to sunset and it was on the evening in on to coast in Charleston SC. So I figured I was getting some crazy interference, which could be coming from anywhere and possibly the quad itself.

    maybe we can figure out the cause

  • That is pretty bad!

    I'm having GPS issues too. I seem to have HDOP of 2.2 or 2.4 even with 9 or 10 sats locked. You mentioned your satellite count, but what was your HDOP during the flight?

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