[Therion] Loop closure / deviation of broken clino

[Xavier Pennec]

Hi Stelios,

The standard values should be ok for the tape and azimut measurement.
They are defined in the file grades.th (in therion/lib) that I included 
(actually we should read 99% of the values within range instead of 95% 
in this file but a small variation does not really matter).

Best

Xavier


Le 05/03/2014 12:16, Stelios Zacharias a écrit :
> Dear Xavier,
>
> Thank you, this is exactly what I was looking for. I would imagine 
> therefore a similar setting will allow small or no changes to be made 
> to the az and the tape measurements when closing loops.
>
> Something like:
>  sd tape 1 cm
>  sd azimuth 1 degree
>
> Cheers,
> Stelios
>
>
> On 05/03/2014 12:02, Xavier Pennec wrote:
>> Hi Stelios,
>>
>> if you believe that your clino measure is plus or minus 10 degrees 
>> (in standard deviation, meaning that 95% of the measures at p/m 20 
>> degrees), then you state before your data:
>>   sd clino 10 degrees
>>
>> You can put a higher value, for instance 1000 degrees or even more, 
>> which means that all measurements (which will be between -90 and 90) 
>> are in the flat part of the Gaussian, i.e. they have the same 
>> probability. With such a sd, the (weighted) least-squares loop 
>> closure algorithm will preferably change the clino measurement than 
>> any other (provided that this allows closing the loops). Now therion 
>> will report the closure error in meter and percentage error and the 
>> only difference should be a decrease of error in X and Y and an 
>> increase in Z (but usually little change on the norm of the 3D error).
>>
>> Hope that helps
>>
>> Xavier
>>
>> Le 04/03/2014 15:52, Stelios Zacharias a écrit :
>>> Dear all,
>>>
>>> I recall a discussion here about using a fairly broad sd value to 
>>> allow loop closure when trying to transfer paper surveys into 
>>> Therion - I may be misremembering.
>>>
>>> I recently surveyed a closed loop with a broken clinometer (spinning 
>>> wildly with no fluid to damp the motion), so for each leg of the 
>>> survey I have distance and azimouth accurately and slope as an 
>>> approximation. How would I set up the sd (if indeed this is how I 
>>> would do it) to close the loop and correct my approximate / 
>>> estimated slopes?
>>>
>>> I look forward to hearing from you.
>>> Stelios Zacharias
>>>
>>> _______________________________________________
>>> Therion mailing list
>>> Therion at speleo.sk
>>> http://mailman.speleo.sk/mailman/listinfo/therion
>>
>
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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
> http://www-sop.inria.fr/asclepios/
> -------------------------------

-------------- next part --------------
grade BCRA3 -title "BCRA grade 3"
  
  # 95.44% of readings are within 0.5m (2 S.D.)
  length 0.25 metres

  # 95.44% of readings are within 2.5 degrees (2 S.D.)
  bearing 1.25 degrees

  # 95.44% of readings are within 2.5 degrees (2 S.D.)
  gradient 1.25 degrees

  # 95.44% of positions are within 0.5m (2 S.D.)
  position 0.25 metres

endgrade


grade BCRA5 -title "BCRA grade 5"

  # 95.44% of readings are within 0.1m (2 S.D.)
  length 0.05 metres

  # 95.44% of readings are within 1 degree (2 S.D.)
  bearing 0.5 degrees

  # 95.44% of readings are within 1 degree (2 S.D.)
  gradient 0.5 degrees

  # 95.44% of positions are within 0.1m (2 S.D.)
  position 0.05 metres
  
endgrade