Skid marks and laser scanner question

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Skid marks and laser scanner question

Post by PDePoister » Fri Mar 10, 2017 4:51 am

I've recently been asked about how to capture skid marks using a FARO Focus3D X330 HDR laser scanner. I have not had the opportunity to try this out with our scanner as we are a crime scene unit. But, we will soon be scanning traffic scenes and I need to know if anyone has any techniques to make skid marks stand out on the pavement. Keep in mind that it rains a lot here and often we are working in the dark so there will be no color information.

Are there special targets that we can use? Does paint show up in the scan? Should I just use evidence markers? Any ideas?

Thanks in advance!

Paul

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Re: Skid marks and laser scanner question

Post by KDersch » Fri Mar 10, 2017 11:25 am

Even with color scans, I have ran into issues in congested mechanical settings where changing the color intensity in ReCap allowed certain features to stand out more than they did in a color view - might be something to look into...

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Re: Skid marks and laser scanner question

Post by dcacioppo » Sun Mar 12, 2017 3:18 am

I do not have the HDR scanner but we have used tent markers or small cones to mark the path of the skid marks for our X330. We also paint the marks before scanning. The paint will show in the scan with color, I have not tried it without color. Fluorescent Pink,
Fluorescent Orange, and White paints have worked well so far.

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Re: Skid marks and laser scanner question

Post by colhum1 » Sun Mar 12, 2017 2:34 pm

I've recently been asked about how to capture skid marks using a FARO Focus3D X330 HDR laser scanner. I have not had the opportunity to try this out with our scanner as we are a crime scene unit. But, we will soon be scanning traffic scenes and I need to know if anyone has any techniques to make skid marks stand out on the pavement. Keep in mind that it rains a lot here and often we are working in the dark so there will be no color information.

Are there special targets that we can use? Does paint show up in the scan? Should I just use evidence markers? Any ideas?

Thanks in advance!

Paul[/quote]

Hi Paul,

We always identify our marks using road paint, primarily to show up in our photographs.
Paint is really good for identification with scans too...however...colours show up differently depending on how you view your scans.
These are all from the Faro x330.

This example shows how paint shows up with the Leica C10:
C10 Road Paint.png
here are a few examples:
Screenshot_1.jpg
Screenshot_1A.jpg
Screenshot_1B.jpg
Screenshot_1C.jpg
Screenshot_2.jpg
Screenshot_3.road.jpg
Screenshot_4.services.jpg
Screenshot_4A.services.jpg
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Re: Skid marks and laser scanner question

Post by PDePoister » Sun Mar 12, 2017 7:19 pm

Thanks for the examples. I'm surprised at how well the skids actually show up in the scans. But, I definitely like the paint results. I'll have to do a paint test to make sure what we're using shows up well too.

Where did you get those little spheres? I really like those.

Thanks again for your help!

Paul

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Re: Skid marks and laser scanner question

Post by dcacioppo » Sun Mar 12, 2017 10:50 pm

We use koppa tarets. They have all different sizes. Talk to Tad and he can help you choose what you need. Otherwise if you are ambitious you can make your own targets out of ornaments, styrofoam balls, glass globes, etc. You can search 'Home made spheres - accuracy' on this blog as well.

http://www.koppatargets.com

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Re: Skid marks and laser scanner question

Post by ClarkCoSheriff » Mon Mar 13, 2017 1:09 pm

The paint will show up great when you scan without color. It will provide great contrast, even in the dark. Here are some shots from an Officer-Involved Shooting we investigated in a rural part of another county. Because the lighting was so poor at the scene, I chose not to use any light at all in order to avoid the funky color and shadow effects from too little lighting. Here is one of the point cloud:
Paint Mark.jpg
And another from Quick view:
Paint Mark 3.jpg
Regarding skid marks when it is wet, I have not tried this as I don't normally scan crashes either. However, I have also thought of the idea previously mentioned of using a marker such as a number placard or a small sphere to mark the beginning, end and points in the middle of the skid mark. Hope this helps.
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Re: Skid marks and laser scanner question

Post by Formula1982 » Tue Mar 14, 2017 11:59 am

If it were myself tackling this, the first thing i'd want to know is how accurate do you need the skid marks?
Maybe scanning them wouldn't be enough to define exactly where they start and stop, which is what I assume you need quite accurately picked up for your needs. I'd consider putting down some white tape adjacent to the extents of the skid mark which should be picked up clearly by the scanner and allow you to define it in the resultant data.

I doubt a camera even with good lighting would be able to pick up the skid in a satisfactory way.

I've scanned alot of race circuits at night and it picked up the skid marks very clearly, just from the intensity values of the data. Skid marks tend to have a much lower reflectance than the surrounding asphalt.

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Re: Skid marks and laser scanner question

Post by PDePoister » Thu Mar 16, 2017 1:31 am

Thank you all for the replies. It sounds like there are a couple different solutions to try. I think the next step is to go out and take some scans to try these ideas out. I'm especially interested to see what happens when the pavement is wet.

Thanks again!

Paul

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Re: Skid marks and laser scanner question

Post by kastopek » Thu Mar 16, 2017 5:58 pm

Good Afternoon,

We have scanned thousands of scenes involving a lot of evidence in different forms. (skids, gouges, scrapes, furrows, etc.) One thing I can tell you is you can never have enough scans out on the roadway. We always paint, unless the roadway "mainly interstate" is too dangerous (in that case we might back ourselves up and shoot evidence and a few common points with total station). Attached is our own color test we ran in color and black and white. Also, if your skids are going off the pavement and leaving furrows I suggest putting different colored ground stakes in to make them show up better. Do not use flags as the scanner pics up on it moving in the mind. If I can be of better help or you have other question send me an email and I will be glad to help.
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