[Therion] Therion Survex Loop Closure Anomoly

[Stacho Mudrak]

It looks like a bug in therion loop closure algorithm. I can have a look at
it, if you can send me the dataset.

Best regards, S.

On 15 November 2010 09:35, Bruce <dangle at tomo.co.nz> wrote:

>  I have a mystery, whereby an overland survey between two fixed points
> gives a correct pdf plan output with;
>
>
>
> loop-closure survex
>
>
>
> (I know it is ‘correct’ because the aerial photograph image matches the
> features surveyed) but if I specify;
>
>
>
> loop-closure therion
>
>
>
> then one of the fixed points is about 150m misplaced in plan and the
> surveyed features are clearly in the wrong place.
>
>
>
> In both scenarios therion.log reports identical average loop errors and
> specific loop error statistics.  The error over a 500m loop is about 2.3%,
> mainly due to a 12m error in elevation (can not trust those gps readings).
> The plan error if one of the points has its ‘fixity’ removed is about 4m,
> and the plots produced are correct regardless of the loop closure method.
>
>
>
> It is a rather large dataset with many underground loops, and four fixed
> surface points.  Two of which have overland surveys between them.  Only one
> of the overland surveys has this problem.
>
> Using Therion 5.3.5.  Can replicate this result on three computers.
>
>
>
> Any theories as to what might be going on and how to locate the issue?
>
>
>
> Bruce
>
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