[updated] compatability ?-LaserScanningAmerica(LSA) prism and laser tracker

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SAttaya
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[updated] compatability ?-LaserScanningAmerica(LSA) prism and laser tracker

Post by SAttaya » Thu Aug 02, 2018 6:15 pm

Has anyone used a laser tracker (Leica 901, etc)
to acquire and measure the location of a LSA/E mini prism or a Leica GPR1, Circular prism,
either in a LSA/E measuring point disk (seat/socket/nest) or anywhere else??


We have a LaserScanning America/Europe(LSA/E) "Mini Prism for Reference Sphere Set".
We typically place it in LSA/E "3D Precision Measuring Point Disk". (same place we put spheres).

We would like to measure the prism location with a Leica 901 laser tracker.

The guy in metrology would like to know if anyone is measuring a Mini Prism for Reference Sphere Set
using Spatial analyzer to drive a Leica Tracker.

We're trying to do a sanity check on our current use of a Leica total station (TS15, 1")
to acquire the prism accurately.

(This may have been asked before and if so I apologize.)

I can acquire a Leica RRR SMR with the total station (longer distance & outside).
I now want to acquire a LSA/E mini prism with a laser tracker (more accurate and inside).
I know about the ATS scan reference system.

TMillington
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Re: [updated] compatability ?-LaserScanningAmerica(LSA) prism and laser tracker

Post by TMillington » Mon Aug 06, 2018 9:36 am

Hi Steve

To be honest, I'm not quite sure what it is you're hoping to achieve.

As far as I'm aware, standard Total Station/EDM prisms are not compatible with Laser Trackers, but if you can achieve a measurement with the Tracker/Prism combination I'd suspect that the accuracy/manufacturing tolerances of the prism will nullify any increased accuracy you hope to achieve from using the Tracker.

As you can aquire measurements to a Laser Tracker SMR target with the TS15, a straight comparison on a fixed/forced centering line measured with the two instruments will give you your sanity check on the TS15 measurements.

If the purpose of using the 901 is to improve the accuracy of your scan control points, then I would look at setting up a control network for the scanning using the SMR placed on fixed standard tracker drift nests, with the SMR replaced with something like https://hubbsmachine.com/laser-tracker- ... 4-pss.html when you scan.
Capture.JPG
Obvious I know, but unless you're using a 'high grade' scanner, the quality of scan and the specification of your scanner is likely to have more impact on the overall accuracy than replacing the TS15 with the AT901.
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SAttaya
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Re: [updated] compatability ?-LaserScanningAmerica(LSA) prism and laser tracker

Post by SAttaya » Mon Aug 06, 2018 1:44 pm

Has anyone ever used a laser tracker to acquire a totalstation Prism?

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Re: [updated] compatability ?-LaserScanningAmerica(LSA) prism and laser tracker

Post by SAttaya » Mon Aug 06, 2018 1:57 pm

TMillington wrote:
Mon Aug 06, 2018 9:36 am
Hi Steve

To be honest, I'm not quite sure what it is you're hoping to achieve.
...
Obvious I know, but unless you're using a 'high grade' scanner, the quality of scan and the specification of your scanner is likely to have more impact on the overall accuracy than replacing the TS15 with the AT901.
Tony,
Thanks for taking the time to cover the options.
Yet another clear, concise LSF response.

TMillington
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Re: [updated] compatability ?-LaserScanningAmerica(LSA) prism and laser tracker

Post by TMillington » Tue Aug 07, 2018 4:03 pm

Hi Steve

I've been running some checks on our AT401 tracker (Leica quoted uncertainty values +/- 15 µm + 6 µm/m), so had a go at measuring to a Leica GPR1 prism at the same time.

The 'good' news is that the tracker can measure to the prism, but applying the prism constant (-34.4mm) in Spatial Analyzer is not as easy as it might be.

The centring accuracy for the GPR1 is quoted as 1mm and I got differences averaging 0.7mm from distances measured to an SMR - so in the right ball park I think.

Which comes back to, given the mis-match in accuracy specifications, why and/or what would you be hoping to gain from using the tracker with the prism?

If the concern is the accuracy, calibration or condition of the TS15 ("We're trying to do a sanity check on our current use of a Leica total station (TS15, 1") to acquire the prism accurately.") then I'd think a set of standard EDM check measurements on a fixed or known baseline is probably the best way to go.
As a gross check, if you can abstract your control network from the scanned spheres and compare with the TS15 derived network that should flag up any significant issues with the TS15 measurements (of course that might be what's prompted your question in the first place).

Hope that helps

Cheers

Tony

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Re: [updated] compatability ?-LaserScanningAmerica(LSA) prism and laser tracker

Post by SAttaya » Tue Aug 07, 2018 5:57 pm

What did you have to do or parameters to set in Spatial Analyzer.

Thanks again for taking the time to address this.

And yes , it is the comparison of the TS15 derived network
to the scanned spheres that brought all of this up.

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Re: [updated] compatability ?-LaserScanningAmerica(LSA) prism and laser tracker

Post by TMillington » Wed Aug 08, 2018 10:59 am

Hi Steve

Spatial Analyzer (SA) doesn't offer measurement to a prism as an option when chosing and defining reflectors and targets for the AT401, so it's not possible (as far as I can see) to configure a prism offset which is then applied to the distance measurement. I had to apply the correction by hand and then manually reduce the measurements to allow for the prism offset.

SA treats Total Stations differently (we use a Sokkia NET 05AX) and does allow for Prism reflectors and varying prism corrections.

I don't know what scanner you're using, but presumably you're getting significant differences compared to the TS15 (over and above any variations due to the scanning of the spheres) which is raising doubts about the TS15 measurements.

For what it's worth, my gut feeling is that if those differences are sufficiently gross to show up in scans from a 'typical' scanner (ie: Focus, 'P' or 'C' series, TX series), and they are down to the TS, then it probably needs returning for service/repair and recalibration. :( But the first step would be to go back to a fixed base measured using the 901 and RRR and check the TS15/RRR combination on that.

If the TS15 checks out then I guess the other obvious checks (which you might have done already) will be the LSA prism (centring correctly and coincident with the spheres, prism constant?) and the scanner (both that is physically operating correctly and that the data is processing correctly)

Regards

Tony

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