trimble realworks georeference

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andrew mc
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trimble realworks georeference

Post by andrew mc »

Hi,
I am running a Faro X330 scanner with Trimble Realworks.
The scan processes fine, however when attempting to transfer the scan to the site datum using the 'georeference' function in Realworks, things get strange.
I use three known MGA coordinates with three scanned sphere targets. The error is 0.005m (acceptable) and the apply button is clicked.
However on review, there is a tilt introduced into the scan after applying the georeference function. previously level concrete slabs are sloping.
Do others have this issue?
I suspect that there is more than a block shift and rotation going on here - maybe a 3D transformation, that gets exaggerated if the control points lack the required geometric configuration.
Either way, the scan is not much good if it cant be referenced to a design file on datum.
Any thoughts or advice would be appreciated.
Thanks, Andrew
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tchaper
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Re: trimble realworks georeference

Post by tchaper »

Hi Andrew,

the georeferencing tool in Trimble RealWorks applies a full 3D transform to the dataset to align with the control points. If some target heights are wrong, you may then get a tilt.
Moreover, in your case, if the three control points are close enough to one another, the 5mm error can actually correspond to a significant tilt angle. This might be what you see. How much is the maximum distance between the three points?

Thomas
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Re: trimble realworks georeference

Post by Daveorde36 »

Hi Andrew,

This is normal for georeferencing, have you tried importing the station coordinates as a txt file and completing the adjustment using target based registration whilst making sure the scan files vertical orientation is fixed? Each scan file should appear blue if memory serves me correctly.

Dave.
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Re: trimble realworks georeference

Post by andrew mc »

thanks for the quick replies.

Ok, that makes sense. the control points were in a straight line up the centre of the job (all I could use) - about 15m then 45m apart, and their main purpose was for horizontal control to get the job on to the local grids. Vertical control could be done later.
So maybe the georeferencing function was not appropriate.
My sphere targets were placed on control points primarily for this datum transfer.
All registration was done using targetless with planes. This saves considerable time setting up and scanning in the field, and the registration comes out great each time.
However, I will investigate the "registration using targets" option though if it offers the 2D horizontal adjustment which is becoming critical to my output.

Andrew.
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Re: trimble realworks georeference

Post by ollydoyle »

tchaper wrote: Fri Jan 22, 2016 1:47 pm Hi Andrew,

the georeferencing tool in Trimble RealWorks applies a full 3D transform to the dataset to align with the control points. If some target heights are wrong, you may then get a tilt.
Moreover, in your case, if the three control points are close enough to one another, the 5mm error can actually correspond to a significant tilt angle. This might be what you see. How much is the maximum distance between the three points?

Thomas
Is it Possible too Lock the Z axis when doing a Goereference, like what it does in Trimblre Business Center where it only translates in x y and z and only rotates about the Z axis
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