Looking for some other IRIS flyers that may be having poor GPS performance.
Only about 1 in 7 flights do I get HDOP lower than 3. After about 40 flights I can only remember it getting below 2 a couple of times. One day it's in the low 2's and over half the time its 3.5 to 5 and getting repeated GPS failure alarms.
Is this normal? With that issue and the alt hold issue where any horizontal flight causes a big drop in altitude I can't really do much beyond fly around in stabilize. I think I can tune the alt hold issue thought.
mp
Replies
I constantly have very poor HDOP here in Colorado, I pretty much only fly in stabilize or alt_hold.
Mine is probably somewhere in between. Usually I get between 8 and 9 sats and a hdop of around 2. There is only one day where I got 13 sats and an hdop of 1.5.
@Joe: For your unexplained 10 meter drop. Did you have a gusty winds that day? I'm experiencing issues with the Barometer in gusty wind situations. See here: http://ardupilot.com/forum/viewtopic.php?f=48&t=7458&sid=8e...
With that I'm in a similar boat as Mark: At times I can only fly in Stabilize mode as AltHold and Loiter will shake IRIS all over the place.
I called 3DR today and am waiting on tech support to return the call. First thing they asked was "what state are you in?". When I told them Texas they said there were no reports of GPS issues in Texas so they must have some areas that have consistent issues.
I struggle with that one. Anyway I have numerous different types of GPS's that show normal performance when this happens.
I'll let you know what they say.
mp
There was some website from the USCG (or was it the FAA?), where you could look up the expected GPS sat coverage for the world on a map. Unfortunately I don't remember where I stumbled over that.
But if you find that website again, it might help you determine if the number of sats you are seeing is the expected max or if the GPS receiver is just subpar.
Thomas just pointed me towards this Sat Predictor site: http://diydrones.com/profile/ThomasJCoyleIII
It's not the one I had used, but actually even better: Punch in your location and it will show you the expected number of GPS satellites and the expected xDOP value. Awesome find by Thomas! Thanks.
I checked the site for today and the time I was flying. It showed I should have 7-8 sats. I had 7.
It showed my DOP availability as about 1.6. I had 3.5 - 4.0.
The site lets you go back in time. I compared the numbers to my flash logs and still found no correlation. The only time I get an HDOP below 3.0 is when I have 9 or more sats.
I think it's a weak GPS board but we will see.
mp
I did have gusty winds during the mission! Thanks for sharing that.
FYI - I'm still running v3.1.2
HDOP is consistently below 1.55 for me with 8-10 sats. Even so, I did have an unexplained 10 meter drop in altitude during the mission, but overall no major issues.
-Joe
3DR called me back in less than 2 hours. They sent me basic steps to try like the Arducopter sat good parameter, do a compass cal and make sure you arm in stabilize mode. Of course I have already tried all of that and informed them as such.
Got a reply right away that another call contact me within 1 day to arrange a new IRIS GPS to try. I'll keep y'all in the loop.
mp