Faro quality setting

Faro S150, S350, X30, X130, X130HDR, X330, X330HDR, M70, Trimble X7, Leica RTC360, HDS6*00, HDS7000, Z+F IMAGER 5016, 5010X, 5010C, 5006H, 5006EX & PROFILER 9012 etc
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Re: Faro quality setting

Post by ghale »

Correct. Higher resolution typically means a longer scan time. Typical scan times for FARO scanners range from 2 minutes to 30 minutes (although you can scan even longer). The longer it scans, the more points it will acquire, thus increasing your density.

I also mentioned distance, because the further away an object is, the more divergent the points will be, because of the way the laser rotates. This is just a matter of balancing the resolution setting and the distance.

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Re: Faro quality setting

Post by crullier »

Would you be able to post images or a 5 minute scan versus a 15 minute scan or maybe even share a sample?
Is there a way to see this info in a scan inside scene or in the properties?

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Re: Faro quality setting

Post by apjokr »

jcoco3 wrote:So we finally had time to run the quality comparison test scans, but we botched it :( Well it was not a total loss. I naively assumed that if the scanner remained in the same place that the horizontal zero start position would be the same for a series of repetitive scans set to various quality settings. Obviously there has to be some small amount of angular error in the base servo or angular encoder so the horizontal zero position has small angular differences, as indicated by the rotations being slightly off in the transformation dialog of each scan in Scene. Silly mistake, and I should have known better. At first I thought the error might have been due to the compass, but we turned off all the sensors except for the inclinometer before conducting the test. We even placed some checkerboards around the scanner position to tie to a total station for back-checking our scans, but because their poor placement I don't think they are sufficient to register the scans together with enough angular accuracy to properly align the scans for comparison. We will try re-run the procedure using a different methodology soon, but until then I wanted to share what was salvageable from the results.

Here are some images of spheres scanned at 1x and 4x quality setting with spheres placed at 10', 30' and 50'
120S_1X_FRONT.png
120S_4X_FRONT.png
As the quality setting is increased the positioning of each point appears to be slightly more organized the range noise also appears to be less random. All sphere fits were automatic/green and rotating the scans to nearly the same angular position the difference in range to each sphere at all quality settings represented less than 1mm of variance, although I am not satisfied with this result due to our inability to nail down the exact horizontal orientation. I think in the next test we will setup the same 3 test spheres, but we will also surround the scanner with many spheres at many different heights and ranges to be used to registered the scans together while ignoring the 3 test spheres. After registration we will re-run the automatic sphere search to find the 3 test spheres and examine the results.

Initial conclusions:
1. Higher quality settings capture more points on a spheres at longer ranges, but I think we all knew that already.
2. As spheres are placed further away from the scanner the weighted importance of each point should increase as the number of acquired points decrease, therefore higher noise overall should negatively effect the sphere fit, but by measuring the distance between spheres the initial results don't suggest a large impact as the spheres from different quality settings all appear to be near the same position(less than 1mm deviation). In short it would seem like even with 85 noisy points on a sphere an accurate sphere fit can still be established.

I plan to provide some tabulated results in excel comparing sphere positions from one quality setting to another and the sphere positions to total station shots after we re-run the experiment. I would also like to compare scanned sphere point coordinates to the scanner's origin in an attempt to asses the range noise per quality setting. This is turning out to be more difficult than I anticipated, but I am confident we can obtain some clear results that are easy to understand in time :)

Full resolution images here:
http://1drv.ms/1yWYCfD
Thanks for sharing this test, I really enjoy reading your posts.
I have just done a test about point density. BUT
I was wondering, We should test the resolution settings instead of quality. I always use 4x quality, but I wanted to know how many points I would get on the same are with different resolutions.
I measured a facade with 1/5, 1/4, 1/2 resolutions and segmented a small area on it, and counted how many points I have there, and how many millimeters does it have between the points.
I got 5mm distance between points with 1/2 resolution from a 15m far distance surface. It looks poor for me.

Tell me please what do you think !
Thank you!

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Re: Faro quality setting

Post by jcoco3 »

Hi Robert,

According to my calculations(which could be wrong) the 5mm seems about right for 1/[email protected]
Please see the new version of my density calculator here:http://www.laserscanningforum.com/forum ... 563#p45563

To increase your density you need to get closer to the surface, increase your resolution setting, or make many more overlapping scans.

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Re: Faro quality setting

Post by apjokr »

jcoco3 wrote:Hi Robert,

According to my calculations(which could be wrong) the 5mm seems about right for 1/[email protected]
Please see the new version of my density calculator here:http://www.laserscanningforum.com/forum ... 563#p45563

To increase your density you need to get closer to the surface, increase your resolution setting, or make many more overlapping scans.
Thank you!
I will examine that xls :shock:
Hm, I heard that my instrument is preferably for indoor scanning, but now it's clear for me that I have to use 1/2 and more scanstations. I would like to take measurments on steel structures BTW. That means it is not quite flat surface like a facade and also dark..absorbing my points. A tough nut to crack.

Anyway, It's good to read your approval. I was wondering that RealWorks didn't show me all of the data.

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Re: Faro quality setting

Post by jedfrechette »

5 mm looks right to me to. Attached is the spreadsheet I use for estimating point spacing and beam diameter based on the scanner spec sheets. Adjust the green cells and it will update tables and graphs below. To see what the values are for 1/2 resolution set the "# of Steps" to 2. Note that at 15 m your beam diameter is also about 5 mm with a Focus so 1/2 is a pretty good resolution as you're not oversampling to much.
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Jed

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Re: Faro quality setting

Post by jcoco3 »

Oooooh fancy :D I have no idea what I am looking at, but I know it is cool! Thanks Jed, hopefully I will be able understand this more very soon. It is nice having floor and wall spacing separated, as that is difficult to imagine in the field but also very important.

I always hoped I could expand my spreadsheet to estimate for a number of primitive objects styles for a given range, but the task seems insurmountable as there are so many different shapes to account for in the real world. Also it would be helpful if there was a way to throw in a low return percentage due to angle of incidence and material reflectivity, but that has so much more to do with the quality setting, that it is even more difficult to incorporate. For now I have to go with my gut, which is not always right :?

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Re: Faro quality setting

Post by apjokr »

jedfrechette wrote:5 mm looks right to me to. Attached is the spreadsheet I use for estimating point spacing and beam diameter based on the scanner spec sheets. Adjust the green cells and it will update tables and graphs below. To see what the values are for 1/2 resolution set the "# of Steps" to 2. Note that at 15 m your beam diameter is also about 5 mm with a Focus so 1/2 is a pretty good resolution as you're not oversampling to much.
Hi Jed, that's a professional chart :)
At least, it is good that I came up with results which proves the statistics :D

I need more scanstations, obvious for me.
Anyway, does anybody use 1/1 resolution? When I'm reading posts, I realized most of us uses lower quality but much more spheres and scanstations.

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Re: Faro quality setting

Post by apjokr »

jcoco3 wrote: Also it would be helpful if there was a way to throw in a low return percentage due to angle of incidence and material reflectivity, but that has so much more to do with the quality setting, that it is even more difficult to incorporate. For now I have to go with my gut, which is not always right :?
Yes, I would be happy knowing the point numbers on different materials. Steel structures painted dark are not so reflective, so should I expect worse numbers, than that table shows?
Moreover...I will measure in shiny daylight...
:?

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Re: Faro quality setting

Post by geowac »

I used 1/1 scans - rarely!

It's boring and I did it on a project we scanned with three scanner because of some time limits...

I postulate that's enough to know the max grid size on an object on the horizon. Because all other grids are denser. In our table is a column with the points in a sphere depending to the distance. That's enough to me, because if I know. 100 points are on the sphere it's ok...

By the way: with photogrammetric it's standard to get a grid size of 2 to 5 mm per pixel (outside, facades). But this is a point to discuss with the customer because in digital images you can zoom in, in printed not!

I prefer to print the results and everything is ok, but if you hand over the PDF he is disappointed!

Cheers
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