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accuracy of recap settings??

9 REPLIES 9
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Message 1 of 10
cc4535
1524 Views, 9 Replies

accuracy of recap settings??

We typically use Scene and we try to get our scans within 1mm mean difference between points and I am not sure if I am reading recap correctly. When I choose the 3 points on a scan and have it match the other scan we see 3 percentages. Overlap  Balance    Point<6mm  my question is would this <6mm be the same as the mean difference between points in Scene? Our client requires a 1mm" min..

Chuck Conley
M3 Engineering
9 REPLIES 9
Message 2 of 10
scott.a.green
in reply to: cc4535

@cc4535

 

To answer your question, "would this <6mm be the same as the mean difference between points in Scene? Our client requires a 1mm" min.". 6mm is a bucket showing the percentage of overlapping points in the scan that fall below the 6mm threshold. Most points will be closer and if you hover the mouse over the result you should see a complete list of the results. 

 

See the following post: 


<6mm accuracy

 

 

 



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Message 3 of 10
Patrick_Aps_9121
in reply to: cc4535

I suppose the 1mm setting is there when you export as a unified cloud (or when you export unified regions)

and also when you import the cloud.

But the setting when Registering is not about what you ask.

 

Message 4 of 10
cc4535
in reply to: Patrick_Aps_9121

I would defiantly like to see better accuracy. We have to use scene to get our engineering scans to the accuracy required by our clients. Will Recap be getting more accurate in future versions?

Chuck Conley
M3 Engineering
Message 5 of 10
rpierceCDRWH
in reply to: cc4535

I need to fully understand this same dilemma.  I cannot share with the client the accuracy of my registered scan project.

Message 6 of 10
amorap
in reply to: rpierceCDRWH

Hi from Spain


Accuracy and Density depends directly of your scan device and the distance between scan location and the target, regardless the software you are using.

 

I have a Faro Focus X130. When I raise the density slider in the scanner, I can see the gap between points in a virtual sphere of 10 meter radius.
Obviously, if my scanner has a 130 m range, far points cant have the same gap. If my gap between points at 10 meters is 2 mm, at 130 meters would be 26 mm !!.
If I need a gap < X mm between points, I need to place my scanner near to the target.

 

Then in order to talk properly about density or accuracy, its very important to consider a new concept: overlapping.

 

Theorically, if we scan an area two times, we get the double density, and the gap between points is reduced to a half. Usually the majority of the scan áreas are overlapped at least two or three times, and therefore the actual values of density and accuracy increases.

 

The "<6 mm" percentage that it is shown in ReCap only refers to a pair of scan locations (the current you are registering), not all the scans registered (or unregistered yet).  Surely you will have scanned the same área from other locations near or far away, and then it will have more points that ReCap is not considering.

 

Regards.

Augusto Mora
Architect & teacher of Building Projects at CPIFP Pirámide. Huesca (Spain).
Revit 2014 certified profesional.
Message 7 of 10
rpierceCDRWH
in reply to: amorap

I have a focus 330, and rarely scan without-50-80% overlap. One thing I like with scene is the ability to see the scan tension when registering scans. I can see my results after registering clusters, and can definitive tell my client that "the scan is accurate to 1/8th of an inch." Registering with ReCap, do I need to change what I say to "the scan is accurate to 46% balance"? It would be a lot simpler to plainly state the tension and overall accuracy as a measurement rather than a percentage - this really has no use, then.
Message 8 of 10
amorap
in reply to: rpierceCDRWH

I'm not a Scene user.


In ReCap, the percentage of overlapping shows only the overlapping of a pair of scans (the ones you are registering).

In my opinión the "overlaping" and  " < 6 mm gap" indicators are only a guide or help in the process of registering a pair of scan locations. When you see an 80% of overlapping it only refers to the current pair of scans you are registering.

There is no way to know in ReCap the average gap between points in an área. ReCap has no any tool to check several important parameters of the registered (and / or unified) point cloud. Only if you have an structured point cloud (not unified) you can obtain a "quality of register" report.

There is no tool to select an area and know what is the average gap of it, then other app is needed in order to obtain a complete quality report. I dont know if SCENE is able to do it. A good (and free) option could be Cloud Compare.

 

Regards.

Augusto Mora
Architect & teacher of Building Projects at CPIFP Pirámide. Huesca (Spain).
Revit 2014 certified profesional.
Message 9 of 10
rpierceCDRWH
in reply to: amorap

Scene has the capability to do that - but ReCap is such a better software. That is a good alternative, your suggestion to use cloud compare. If it didn't take such a long time registering 60+ scans, I would do a comparison of results!
Message 10 of 10
dgorsman
in reply to: rpierceCDRWH

I don't have SCENE, so I'm not certain about what exactly they are providing as an "accuracy to 1/8 inch".  Perhaps some of the SCENE users could provide some contextual detail.  I have a sneaking suspicion that we're comparing apples and androids here.

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