[Therion] Loop closure / deviation of broken clino

Stelios Zacharias stelios.zacharias at selas.org
Wed Mar 5 12:16:09 CET 2014


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
>>
>> _______________________________________________
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>




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