Hi Bruce,
With the help of the latest snapshot solving the crash issue, I found
the source of these large distortions. The loop closure that I am using
is The are due to the limited numerical accuracy (float rather than
double somewhere?) in the weighted least-squares for error compensation
when we put very large standard deviations (in my case "sd length 400
m)". I had indeed shots for far away for triangulation, and since the
length is estimated a posteriori from the map, I wanted to put a very
high confidence interval on it. Getting down to a stddev of 50 m solves
the problem. Thus this problem is different from the one we experienced
in 2013.
Xavier
Le 10/09/2020 à 07:33, Bruce Mutton a écrit :
Xavier
I did have a project that distorted part of a loop 400 m vertically too far
downwards. Changing from Therion loop closure to Survex loop closure resolved
the problem, and so I have retained that setting ever since. That may have
been in 2013, or maybe earlier.
On a few occasions since I have checked to see if that problem still
manifested, but it did not. I never figured out why it did it for only a
window in time/Therion versions.
Bruce
-----Original Message-----
From: Therion <therion-boun...@speleo.sk> On Behalf Of Xavier Pennec
Sent: Thursday, 10 September 2020 09:05
To: therion@speleo.sk
Subject: Re: [Therion] Bug with uncertainty on fixed station on windows 10?
Well, on my side, my projects with multiple fixed points with uncertainty that
were compiling last years are now generally crashing at compilation. However,
since I changed computer, therion and survex version, it is difficult to single
out the reason.
With no loop and several fixed points with uncertainty, it seems to crash
systematically like in the example I posted. When it does not crash with
multiple loops and multiple fixed points with uncertainty, it can either gives
a .3d output that seems reasonable in aven, or it can displace one of the fixed
points kilometres away, either in horizontal or vertical direction! Just fixing
a point at 950 altitude can output a 3d file where the altitude is at
-4000m.... A new way to explore abysses! I have just looked at the .3d result
so far since I have not drawn all the maps yet in the cases where it compiles.
As soon as I manage to set up a mock-up example, I will post it to document
this amazing behaviour.
Best
Xavier
Le 09/09/2020 à 22:34, Bruce Mutton a écrit :
I forgot to point out that most of my projects probably have multiple fixed
stations with uncertainty parameters set. I don't think I have experienced any
problems, at least in recent times and with recent versions of Therion.
So your example is interesting.
Bruce
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--
-------------------------
Xavier Pennec
Senior Research Scientist / Directeur de recherche
Asclepios project-team, INRIA Sophia-Antipolis
2004 Route des Lucioles, BP93
F-06902 Sophia-Antipolis Cedex, France
+33 4 92 38 76 64
+33 6 78 35 16 90
https://team.inria.fr/epione/en/
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