GPS Satellite Numbers Question

Running on ArduCopter 3.1.5.

Had a question regarding the number of satellites needed for a GPS fix.

Why is it that ArduCopter needs a large number of satellites (far more than 4) to run in any sort of GPS-enabled mode? Since 4 are the actual number needed, why is it that 11+ are needed? Maybe I missed it, but is this just a setting that I can safely lower?

@apmarcus,
In the GPS-enabled mode you want an HDOP of less than 2.0 I believe and you are not going to get anywhere near that number with only 4 sats. An HDOP of less than 2.0 can take anywhere from 8 to 12 sats depending on your location.
Regards,
TCIII GM

So am I correct in saying that if we get rejected on trying to arm, it is because our HDOP is not low enough?

If somehow we did have an HDOP of 0.5 with 5 satellites it would arm in that case?

Is this a setting that can be tweaked somewhere or hardcoded down in the bowels of the code?

@apmarcus,
Good luck getting a HDOP of .5 with just five sats.
Be adventurous and try looking at the Full Parameter List.
Regards,
TCIII GM

I believe there are two numbers, HDOP which must be lower than 2.0 by default, as well as the minimum number of sats, which is 6. Both have to be satisfied, but both settings are adjustable.