Spike in HDOP / Loss of GPS

[Skeets]

I had a flyaway incident yesterday (Incident using Typhoon H Flight Planner. Could someone please evaluate?) and after reviewing the telemetry data on webflightpath.com, it looks like I lost GPS and the HDOP was as high as 12.75! I know nothing about HDOP other than it is supposed to be low (the rest of the flight, the HDOP was between 0.6 - 0.8 and I had between 16 and 20 satellites).
What would cause this midflight?
Does a loss in GPS cause a high HDOP or does a high HDOP cause a loss in GPS? Has anyone else had this issue? Im not feeling very confident in the H because of this.

 

[Rayray]

Simply Google HDOP and you'll find tons of info.

 

[Skeets]

Simply Google HDOP and you'll find tons of info.

I wasnt really asking someone to explain what HDOP is, per se. As you said, I could simply Google that myself. I guess it was more of a question of whether if anyone else had this issue with the Typhoon H. My other (cheap) drones that have GPS have never had an issue with HDOP or a fly away in midflight (However, there were times that they would not arm if the HDOP was above 2)

 

[Rayray]

What would cause this midflight?

If GPS Sats are in normal configuration, my understanding is that trees, buildings, canyon walls, etc. that come between the lower angle Sats and the GPS receiver, the TH, cause the HDOP numbers to go up, be high. H in HDOP being Horizontal.

Your GPS receiver needs those Sats at lower angles to determine precise horizontal location. If the only Sats received are more "overhead", the HDOP number will be high.

Generally, the TH solution is to fly at a higher altitude, to avoid that shadow effect. Also another good reason to practice flying with GPS off.
The TH GPS automatic cutoff point? I have no idea.

Happy flying.

 

[PatR]

People need to understand GPS is not 100% reliable, position accuracy is not consistent, interference is always possible, equipment sometimes fails for various reasons, and that it should never be 100% relied upon without having a back up system of some sort. If you had a true flyaway there would gave been a fault between the compass and GPS. It happens sometimes, and it happens with every make of consumer drone products. Rather than try to beat the thing to death with endless trouble shooting, call Yuneec's CS and open a problem report. That's where the problem will ultimately be handled anyway.

You pretty much answered your HDOP question at the end if your last post. Yes, elevated HDOP is bad, and HDOP will increase tremendously with a GPS failure. Google/Wiki the definition of HDOP. Faster and easier than having people lay it all out.