ppp averaging and circular error of probability

[gpsd]

Yo Gary, dear All,

environment
hw: raspberry pi4, Ublox ZED-F9P Expansion from uputronics
sw: Debian bullseye, gpsd: 3.24.1~dev (commit 9c5c09a7b049c4e5b65470aa2ef65c0295e98007)

I run PPP in averaging mode several times as described in https://gpsd.gitlab.io/gpsd/ppp-howto.html or "man gpsprof" with different number of fixes. I did it for 6 hours, 1 day and 2 days.

When I display the result is see for example results like this:

CEP 50% = 0.6m , CEP 95% = 1.1m , CEP 99% = 1.9 m

So far all fine.

Recently I run it for 3 days and I got a strange result:

CEP 50% = 0.595m , CEP 95% = 1.469m , CEP 99% = 1.423m

How can it be that the probability for 99% is smaller than for 95% ?  In a sense of statistics not possible.

If someone is interested I can also support the 10mb plot file.

I also calculated the distance between the different results. They are all below 4 cm. So I am not sure if this CEP gives a useful information at all. 

// Hans

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