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3D Laser Scanning: The Best Way to Preserve Evidence on Construction Site Accident Scenes

Q. What do cranes collapsing in New York and Missouri and a parking garage collapse in Florida have in common?

 

A. 3D Laser Scanning was used to capture and preserve evidence on each of these accident scenes.

 

Long used by criminal prosecutors, 3D laser scanning is rapidly working its way into the world of civil litigation. The more complicated the environment, the more value 3D laser scanning can add to site preservation and collection of evidence.  

 

This technology is particularly suited to construction site accidents because they are some of the most complicated environments that litigators face.  

 

Dynamic and ever-changing, construction sites can seldom be preserved for the timeframe that it takes litigants to get to court, much less conclude discovery. Similarly, due to the complicated events on a construction site, it can be difficult to capture all relevant evidence and accurately demonstrate witness lines of site and other perspectives.

 

3D Laser Scanning overcomes all of these difficulties.

 

How it works

3D laser scanners are set up on tripods and use light to measure and record the horizontal and vertical position of everything they can “see.” They capture data from each setup in less than five minutes and are moved around to different positions to collect data from every angle. 

 

This data is used to produce a 3D world that can be visited by lawyers and experts at any time for site analysis and data collection. This data can then be turned into demonstrative exhibits for the Judge and jury.

 

Traditional data collection vs. 3D laser scanning

Site preservation of a construction accident scene is typically done by one of the following methods: 

 

1.      Hand-drawn site sketches on 2D blueprints, plus 2D photographs

2.      Land surveying total-station measurements

3.      3D laser scanning, plus 3D spherical photography

 

Hand drawn sketches based on handmade measurements are commonly used to provide rudimentary 2D diagrams for use in litigation. However, in addition to providing two instances in which human error can be introduced, site sketches are time-consuming and invariably incomplete.  Photographs certainly help paint a picture for the Judge and jury, but parts of the picture are lost in translation.

 

A land surveying total station increases the accuracy of a site sketch. However, each point must be known at the time and deliberately collected. Once the site is altered, there is no opportunity to collect additional data. Plus, the limited number of points collected by this method makes constructing an accurate 3D model difficult, and thus, less likely to be admissible in court.

 

3D laser scanning addresses all of the inaccuracies and inefficiencies by providing fast, detailed, accurate, and complete information of even the most complicated environments. Perfect as-built information can be reviewed and analyzed at any time without the need for a site visit.

 

Lines of site from any point can be reconstructed. With the addition of spherical photography, the virtual world is indeed a perfect representation of the site.

 

New tools provided by 3D laser scanning technology

3D laser scanning also gives litigators new tools that were previously too pricey or just unavailable. For instance, lawyers and experts can now easily:

 

·         Visit the construction site from anywhere in the country

·         Virtually walk around the construction site and enter any building

·         Customize viewpoints to simulate those of witnesses and actors on site

·         Overlay scanned data onto photographs and measure the distance between any points

·         Preserve data that would not have been collected upon original inspection

·         Preserve data from inaccessible areas (e.g., ceilings, unsafe areas, remote locations)

·         Create a 3D model that is accurate and admissible

·         Create video fly-throughs of the job site for the Judge and jury, including animation simulating the actual accident.

 

Case studies

Crane accidents – Crane accidents are, unfortunately, a relatively common occurrence. Cranes have completely collapsed, killing and injuring construction workers in New York City and Bellevue in 2013 and Miami and Kansas City in 2008.  

 

After these accidents, nobody wants to leave the site intact. Rescuers need access. OSHA wants the site stabilized. Owners and contractors want to continue with construction. 3D laser scanning quickly collects evidence for litigants, allowing the site to be mediated without risking spoliation of evidence.

 

Additionally, these sites are unsafe until the failed structural members can be removed. For instance, after the Missouri power plant crane collapse, OSHA erected barriers to prevent anyone from entering the scene of the collapse. However, since 3D laser scanners take measurements of anything visible, forensic site data was still able to be collected.

 

The 3D nature of the data preserved allows litigants and their structural engineering experts to make more accurate theories about the mechanisms of failure. They can work backwards to determine the causes and orders of failure that led to the collapse. It also works to disprove claims made by others.

 

Miami parking garage collapse – In October 2012, a parking garage being constructed for Miami Dade College collapsed on itself. Each floor collapsed on the one below like a stack of pancakes, killing and trapping workers inside.

 

Obviously, this site needed to be cleared to locate victims, address unsafe conditions, and finish the construction. Within 24 hours of the collapse, a 3D laser scanning crew was onsite. As a result, existing site conditions were preserved so that rescue and demolition could proceed.

 

Conclusion

3D Laser Scanning is the superior method for preservation of evidence on construction site accident scenes.

 

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David Headrick has over 20 years of experience in the surveying, engineering, and legal industries, both as a project manager for LandAir Surveying and as a lawyer in private practice.  He has represented numerous land surveyors, designers, architects, contractors, and other industry professionals throughout his career.  Today, David serves as an executive and project manager for LandAir Surveying Company, Inc., focused on developing and managing the company’s 3D Laser Scanning Division.  Contact him at (865) 599-0148 or dheadrick@lasurveying.com. View his LinkedIn profile here.

3D Forensic Scans: Three civil applications

In my travels along the 3D laser scanning superhighway, I’ve spent a lot of time talking to criminal forensic experts. This group was one of the earliest adopters of laser scanning technology and I’ve had the pleasure of meeting agents with the FBI, the Secret Service, and even generals and admirals who are familiar with its capabilities.

In my experience, the most advanced groups in the specific application of the technology to prevent and investigate crimes have been the Secret Service and Scotland Yard. Both have programs written specifically to analyze the data and use it proactively to protect kings, queens and presidents.

High definition scanning allows you to check every site line – not just one or two.

Our firm has worked on several “criminal” projects over the years – some supporting the prosecutors and their evidence and others supporting the defense teams and their clients. But we also work with the litigation and documentation of forensic evidence for civil or construction projects.

Many jobs require our expertise to go out and document the existing conditions of a site. We have literally traveled from Montana to Texas to Georgia working with clients on various cases.

Perhaps the most famous civil forensics projects were the scans used for analysis of the World Trade Center attacks and the Minneapolis bridge collapse. On both of these projects, the scan data after the destruction of the structures was used to determine exactly what caused the failure.

Obviously, in the World Trade Center, the initial impact of the plane created the fire ball and damage, but it was the fuel in the plane that heated up the beams in the structures and ultimately caused them to fail, each floor collapsing on the one below as the entire structure came down. The melted beams were documented with laser data.

Structural Integrity

One of our first projects was scanning a three story parking deck. During the initial walk around, we could tell that the deck – even though made of concrete – was warped and some of the columns were out of plumb. Other areas were cracked and stressed.

We produced plans and models with the data and structural engineers were able to determine that the structure was unsafe. Because of the density of the data sets, engineers were able to look at all surfaces rather than a few strategic spot shots before making their final determination.

By being able to look at the line of the vertical columns through the building, engineers could tell that the cost to fix the failing structure would be much larger than building new.

Large Vessel Analysis

We also had another project where we were asked to scan a large containment vessel that held various types of liquid depending on the product being produced or stored.

In this type of investigation, we were able to document that a certain vessel was out of plumb, warped or bent. This information was then used to determine if the vessel was safe and, if not, how and when to replace it before a failure occurred.

Settlement Monitoring

Being able to monitor when and how much something is settling is very important to a property owner. We recently worked on a very large project in the western United States that involved a large platform used for loading and unloading products.

In this case, one long section had settled much more that the specifications allowed and had begun leaning at a dangerous angle. The engineer showed me previous surveys and I asked him why they needed us if they already had survey data on the structure.

He explained how the parties involved were having difficulty understanding the traditional survey data and its implications.

Once we scanned the platform in 3D and modeled it, it was quite obvious to everyone how badly the shape of the original structure had changed, as well as the principal cause of the failure. This helped move the group discussion from, “There isn’t a problem,” to “How do we get this fixed?”

We have completed many other civil forensic projects for engineers ranging from dam failures to vertical wall failures and even construction slabs that were not level or flat. The common element in all of these projects was that the use of laser scanning technology was the perfect tool to document the conditions and the data was easy to interpret and model into a visual form that everyone could understand.

Forensic scanning of crime scenes will continue to grow, as will the 3D laser scanning of complicated civil projects. 3D laser survey data is becoming mainstream in analyzing the cause of catastrophic civil construction failures. If you know how something fell to the ground, you can usually tell what failed first.

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Tate Jones has over 40 years of experience in land and aerial surveying and was one of the country’s earliest adopters of 3D laser scanning technology. A nationally recognized expert in the field of 3D data capture, he has worked with hundreds of clients in the engineering, architectural and construction industries. Contact him at tjones@lasurveying.com or visit www.landairsurveying.com.