Dual axis compensator VS IMU

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Matt Young
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Re: Dual axis compensator VS IMU

Post by Matt Young » Thu Feb 14, 2019 7:56 am

JohnBunnFARO wrote:
Thu Feb 14, 2019 4:19 am
As far as the Focus S dual-axis compensation/inclinometer/etc., they are equipped with a Dual-Axis Inclinometer. This is essentially how it works https://en.wikipedia.org/wiki/Inclinome ... clinometer.
So the Faro S does have an Dual Axis Inclinometer (DIA). And Not a Dual Axis Compensator (DAC). It's just that the way it's worded on the website seems miss-leading. whatever the difference (And I don't think there is much difference in the final result now), It's just nice to hear the correct terminology stated for things.

I'm really enjoying being a Faro user at the moment (having been a Leica user for so very long).

Great post by the way John. The Forum needs folks like yourself.

And BTW whatever accuracy the scanner can provide - Always back it up with some good old fashioned total station control ;)
If you want to make something simple, then take one thing away that still allows you to do the job. Don't add two more things, and say they both make it easier.

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Re: Dual axis compensator VS IMU

Post by smacl » Thu Feb 14, 2019 9:18 am

JohnBunnFARO wrote:
Thu Feb 14, 2019 4:19 am
Also, Just last month, ASCC conducted another massive independent study where all major manufacturers sent out their own engineers to compete for accuracy, flatness, levelness, etc. The scanners in the study included FARO S150, Lieca P40, Lieca RTC360, FARO X330, FARO S350, and Trimble TX-8. Guess which won? Here is the link to that study https://www.bkf.com/ascc-3-d-laser-scanning-study/
Interesting reading, thanks for sharing. Reading it I'd note that "the participants included personnel from four contractors, two consultants, and representatives from two laser equipment manufacturers" which included testing 4 Faro scanners, 3 Leica scanners and 1 Trimble. No Z+F, Reigl, Topcon so it is hardly fair to say all major manufacturers were represented nor were they equally represented, given that among the 8 scanners there were 2 S150s and 2 P40s. With respect to picking a winner, I'd say it is clearly the people that carried out the study in terms of illustrating the efficacy of laser scanning for this task, which was clearly their goal. Given that there were two S150s and two P40s it is interesting to see that the range of errors when using the same instrument was as high as the range when comparing different instruments, similarly the range of errors when observing on different days using the same instrument and operator. The study also notes "each participant worked independently. All were instructed to use what they considered to be best practices for the work" which as any surveyor will tell you indicates that error is as much down to application of best practice as the colour of the survey instrument. As such, while this is a great study regarding the efficacy of the technology, it doesn't say much to me about the different instruments as there are far too many confounding variables and a very small sample size in terms of numbers of instruments.

What it does illustrate really nicely is that if you're going to get a new scanner, rather than reading too much into the specs, get kit from the different manufacturers on a site that corresponds to your needs, get them all to measure the same site, and compare the results.

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Re: Dual axis compensator VS IMU

Post by danielgadowski » Thu Feb 14, 2019 10:20 am

Matt Young wrote:
Thu Feb 14, 2019 7:56 am
JohnBunnFARO wrote:
Thu Feb 14, 2019 4:19 am
As far as the Focus S dual-axis compensation/inclinometer/etc., they are equipped with a Dual-Axis Inclinometer. This is essentially how it works https://en.wikipedia.org/wiki/Inclinome ... clinometer.
So the Faro S does have an Dual Axis Inclinometer (DIA). And Not a Dual Axis Compensator (DAC). It's just that the way it's worded on the website seems miss-leading. whatever the difference (And I don't think there is much difference in the final result now), It's just nice to hear the correct terminology stated for things.

I'm really enjoying being a Faro user at the moment (having been a Leica user for so very long).

Great post by the way John. The Forum needs folks like yourself.

And BTW whatever accuracy the scanner can provide - Always back it up with some good old fashioned total station control ;)
Here, Here!

Great post by John. Great to read a good response that clarifies things. As I previously stated - phase scanners of past and current have inclinometers, not compensators. It is true that they gotten more accurate and the whole process of putting all of the scans together has moved on quite a bit, which means that you can treat such data with more confidence. Still, as Matt pointed out - if you want to be certain - use a TPS, no matter if its a DAC or DAI :)

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Re: Dual axis compensator VS IMU

Post by jedfrechette » Thu Feb 14, 2019 5:26 pm

What's the difference between a DAI and a DAC?
Jed

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Re: Dual axis compensator VS IMU

Post by MomentEng » Mon Mar 04, 2019 7:59 pm

JohnBunnFARO wrote:
Thu Feb 14, 2019 4:19 am


These scanners also offer on-site compensation, which can be performed at any time to greatly improve the scanner's accuracy and noise level. The noise level improves quite a bit, going from [email protected] to [email protected] The on-site compensation process takes roughly 10 mins to perform, and it honestly only needs to be done once a month or so. It is kinda like adjusting a scope on a sniper rifle to account for wind, in a sense. (terrible metaphor, i know)


This inclinometer takes an initial reading before the scan and another reading at the end of the scan. We also have GPS, Compass, Altimeter, and On-Site Registration constantly updating scans to cloud data or tying to survey control, depending on what settings are chosen by the user. We have tons of independent tests performed by high-level surveyors that prove our leveling accuracy. The ASCC performed an official test of our scanner alongside a total-station (Lieca, actually) and a dipstick. Our levelness was within 99.91% of the total-station throughout the entire tests, and we were better than 96% of the dipstick. It is actually one of the main studies that proved laser-scanning should be officially standardized for FFFL measurements.
John, thanks for that long post...its filled with good information and gives me much more confidence in my S70 unit. I have a few questions...

1. how do you force the scanner to do the onsite compensation?

2. When I start a new scan project, the first scan I take after the unit powers on has what i think is a calibration revolution first, then the scan is collected, then another calibration revolution after...all other scans after that, it only does a calibration revolution after the scan, not before. Is there an option to force it to do a calibration before and after each scan?

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Re: Dual axis compensator VS IMU

Post by tbwester » Tue Mar 05, 2019 4:47 pm

cool report.

makes me glad I can take a section and examine accuracy that way :).

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