3D Scanning and Forensic Applications

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3D Scanning and Forensic Applications

Post by 3DForensics » Mon Aug 03, 2009 2:10 am

Hello All,

I am pretty new around here, but I wanted to discuss something that is very dear to me....3D Scanning and Forensics. I would like to start this thread as a means to discuss issues, techniques and such related to 3D scanning and Forensics.

To start things off, I'll just thow some things out there for discussion....

I think there is a bit of miscommunication from the media about the usefulness of 3D scanners. They make it sound as if you have all the answers once you have collected a scan at a crime scene. This is far from the truth. In fact, it is an extremely dangerous situation when people start relying on the technology to "find" things that could have been found at the scene of a crime by an experienced investigator. In my opinion, it's is much easier to lose something in a 3D scan or have something go unnoticed when compared to actually being present at a scene.

I am particularily curious about how people quantify the data in terms of accuracy? What kinds of errors can one expect in a long range scan from registering 5 or more scans? What about collecting data from specular, shiny and reflective objects?

I am curious to hear what your experiences have been.

Cheers,

Eugene

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Re: 3D Scanning and Forensic Applications

Post by Alexander Freydin » Mon Aug 03, 2009 6:17 am

Try to contact with user http://www.laserscanning.org.uk/forum/m ... file&u=432
Hi wrote about his experience last year...

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Re: 3D Scanning and Forensic Applications

Post by pburrows145 » Mon Aug 03, 2009 8:44 am

Hi there,

There are a number of police forces using the technology in the UK - they do not use the information for 'finding' anything, only presenting it in a court-ready/allowable manner (although some may argue that more in-depth interpretations may be derived from using the full 3D dataset away from the scene).

Many UK forces have imaging divisions which put together 3D fly-throughs from the data, some are even using web-based plug-ins to present the data, and even proprietary software, in-court.

The scanners are not THE solution, just A solution - part of a wider tool-kit including photography, video, hands on collection, illustrations, plans - the list goes on.

As far as the importance of scanners for this sector, the impact is immense, you only have to see a forces' collective jaws drop to realise they like the technology & what can be achieved with it.

There are few police guys on the forum so I would be interested to hear their thoughts...

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Re: 3D Scanning and Forensic Applications

Post by 3DForensics » Mon Aug 03, 2009 1:37 pm

I would have to agree with your comments completely. I like to think of the 3D scanner as a measurement and visualization tool, albeit a very powerful one.

I think my comments were aimed at some of the TV shows and articles that I have seen that talk about how 3D scanners are cracking tough cases and such.

If there are any Police on the forum, it would certainly be interesting to here how you have used the scanners in the field and even more importantly, what has been done with the data once it was collected!

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Re: 3D Scanning and Forensic Applications

Post by Z+FUK1 » Mon Aug 03, 2009 3:07 pm

Hi all

I totally agree, 3D laser scanning is a great tool in Forensics but it shouldn't be seen as a 'be all and end all' I can't imagine that a laser scanner would ever replace good investigation work.
However saying that, it can achieve a lot that other tools just can't manage.

I had a conversation with the Vice President of the IAFSM not so long ago about its role in accident documentation. (Eugene, see http://www.iafsm.com/)
It was fascinating to me, that without a tool to capture a crash scene, the involved vehicles had to be physically moved and rotated in order to reconstruct the scene of events!

One of the benefits I see Eugene is in being able to store the data. I imagine that crime cases must come under review, or become relevant to other cases. I wonder whether the ability to access this data at a later date would be of much interest.
Of course there's also a lot that can be done with laser scanning software, such as working out the height of the culprit in a crime scene, reconstructing gun shot angles or verifying eye witness testimony. The speed of a crashed vehicle(s) can be understood in part by creating a vehicle crush profile. For complex or serious crush profiles, thousands of measurements can be taken with a laser scanner. Can you imagine doing the same with a tape measure or other rudimentary device?

However saying that, my background is more marketing than technical and the big problem I see in that respect is in cost; 3D laser technologies are often just too expensive for Police forces, at least in the UK. When you couple this with what I perceive to be a relatively low level of awareness, I don't think we're quite there yet.
What does everyone else think?

Thanks

Andrea
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Re: 3D Scanning and Forensic Applications

Post by 3DForensics » Tue Aug 04, 2009 6:22 pm

Hey Andrea,

Thanks for chiming in.

Cost is definitely an issue from my perspective as I would love to purchase a mid-long range scanner and have explored this for a few different units, but being self employed means that you really need to be certain that business will be there or you will quickly find yourself in a world of financial trouble.

The ability to capture and record enormous amounts of data is only part of the equation. The other part is what are you going to do with all that data?? I believe that there are still going to be major developments in the software arena and in my opinion, the data analysis, manipulation and visualizaiton part is far more involved than the actual scanning.

Regards,

Eugene

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Re: 3D Scanning and Forensic Applications

Post by dmercel » Tue Aug 04, 2009 10:24 pm

Hi Eugene,

You ask some interesting questions that I think have quite complex answers. I think many people would agree with your statement about the media, and I think that generally the media tend to simplify and sensationalize almost everything. However, this does have the positive effect of increasing expectations of capability and helps to drive development and efficiency in many areas. The CSI effect!!

It is a sad truth that not every crime scene can be attended by an experienced investigator and therefore it is beneficial to have tools such as laser scanning / photogrammetry and videogrammetry to fill this void and allow a wider audience to consider a scene without attending it. This is not to say that it should always be relied on, but is nevertheless a valuable asset when other assets are not available. It is also very valuable when scenes contain hazardous agents that restrict operatives from entering and making direct assessments. But, as with every tool it must be used responsibly and in an appropriate manner and there be explicit understanding of the capabilities of such systems.

Generally, there is a procedure that is followed for each crime scene investigation, and in my experience I have not found that one tool eclipses another. Therefore, you do not find laser scanning replacing photography of a scene but instead complimenting it to provide a more in depth perspective. Hence, it is helping to improve investigation rather than replacing it.

Quantifying accuracy is a complex process and is dependent on numerous factors, as I am sure you are aware. To list a few: The hardware being used, atmospheric conditions, distance of observations, condition of object being observed, material of object, angle of observation to the object. The list goes on. Errors can be numerous and are dictated largely by the methods of capture. For example placing targets in a scene is one way of controlling it, however, if the target placement is bad then the absolute position of the scan may be less accurate than intended.
These errors can be increased by bad, or incompetent, processing practices, especially regarding registration.

To attempt to address this, one solution is to take check measurements with other instrumentation to help validate the survey. This can be in many forms such as points, control points, planes, measuring rods, tape measurements of objects within the scene and calibrated imagery. However, you have to have the software and expertise to incorporate all of these into the original survey data to effect a comparison.
It is also important to keep in mind the intentions of the survey and required accuracies to ensure the right method of capture is being used. It is a commonly held opinion that CSI requires absolute accuracy, however, this is not always the case and it needs to be considered what purpose the data capture serves and what it may be required to prove. In many cases the placement of an object to within mm is not necessary, but more its general position relative to other objects. It is always useful to bear in mind that some CSI's are perfectly possible without any measurements and many cases have been solved without using any specific measurement technologies. It always comes down to appropriate and responsible use of the assets and technologies available.

Hopefully, this helps to clarify some of the points you raised. I think it is quite a complex field and associations like the IAFSM are trying to help consolidate expertise in this subject to ensure more consistency in CSI measurement practices. I do recommend you look into this association further if you are involved in this type of work.

Cheers,

Dave

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Re: 3D Scanning and Forensic Applications

Post by 3DForensics » Wed Aug 05, 2009 12:08 am

In fact, I am aware of the IAFSM and visit their site regularly. I am currently not a member though, however I believe it is an organization well suited to my interests so perhaps I might be at the next meeting.

I think you raised some good points about the control points and required accuracies.

My background is originally in the aerospace industry which has tight tolerances (about 0.002") for just about every part. When I first realized what I was dealing with in the Forensics industry, I was amazed at how much allowable tolerance there really was. The fact is that many times the assumptions and methods made in an investigation (especially vehicle accidents) far outweight any of the errors of a total station or 3D scan. So, if you are down to a few millimetres, it's usually in the ballpark (but that doesn't always stop me from tyring for better :D ).

Also, I use a robotic total station for many of my surveys and I can't emphasize enough how important it is to have good control points (several if possible). I always provide a verifaible measurement with a long tape measure so I know the numbers agree and what my potential error might be. I say might simply because the fact that you checked a reference measurement with a tape measure doesn't mean that your measurement of interest has the same type of error. So, it might best be described as an indicator or potential error.

On another note, I heard that Z+F have some tools specific to crime reconstruction. Does anyone know of other companies that have similar tools that are related to 3D scanning?

Cheers!

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Re: 3D Scanning and Forensic Applications

Post by Matt Young » Wed Aug 05, 2009 2:09 pm

Dave,

It is really good to see someone with a complete understanding of the true nature of Survey and all the factors involved. To record a true picture of a piece of reality is far more complex than some people may give credit for. To be able to take into account all of the parts and the way they effect each other is at the root of a good survey. The need to provide accurate information in such a serious line of work, is in my opinion, a good way to bring out the best in survey methodolgy.

The main thing that the Laser scanning community should always remember, is that a laser scanner, although expensive is another usefull tool in the box, This is key to its success.

Matt
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Re: 3D Scanning and Forensic Applications

Post by andyevans » Wed Aug 05, 2009 2:58 pm

Hi Eugene,

Dave has supplied a very comprehensive reply and counter discussion points! Registration approaches and control accuracy is just one topic that I can sound off on for hours if you like :-)

I would like to echo the majority of statements made in this discussion. My impression of forensics so far is that many quality tools are required to reach a solution and dimensionally record the required evidence.

I also understand that some investigators would prefer to develop their own tools for analysis. "Let the forensics experts develop tools based on their expertise not the manufacturers devleop tools based on their perceptions of what is needed."

However, with my manufacturer hat on, I would like to highlight some thoughts from a recent forensics exercise that I was fortunate to be involved with. I will showcase a tool that is commercially available now (but please choose to ignore the tradenames if you wish so we do not cloud this discussion with marketing!)

Consider non-contact "remote sensing".

Laser Scanning with Survey Workflow (Occ/BS control) - This minimises requirements for targeting in the scene. Further a time-of-flight scanner, allows the user to focus their detailed scanning on the areas that matter, and in many cases may prove to be a more practical tool. Although, as you know all scanners have their pros and cons. Ultimately the user has to chose the characteristics that work best for their application.

Imaging Total Station - High angular accuracy, high distance measurement accuracy, but also a photographic record of all measurments. As well as highly accurate discrete point measurement, the Topcon IS is also capable of light scanning duties (this is dicsussed elsehwere in these forums).

Stereo-photogrammetry - Nowadays off-the-shelf digital cameras can be used to ahcieve high accuracy 3D models and generate surfaces that compliment scanning deliverables. Quick, and if used correctly also possible to achieve with minimal or no contact at the scene. The ImageMaster software can generate models with no requirements for targeting other than object points that can be indentified in the pair of photos.

The key though is having a single software to bring all this information together. ImageMaster could be the glue in this case to keep all the features of each instrument available to the end users but have all the relevant survey information in one place, ready to go for analysis by the forensics expert.........

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