Sometimes I don’t have to look past the front page of the local newspaper to see a good example of laser scanning in action.
Tragically, there was a police-involved shooting in Cobb County, Georgia, this past weekend, as reported by the Atlanta Journal-Constitution. The suspect allegedly robbed a gas station and then led the police on a high speed chase. The chase ended on I-75 when the suspect pointed a weapon at the police officers and was shot dead.
This was a very unfortunate incident, but the impact on the community was far lessened due to the outstanding work of the Georgia Bureau of Investigation.
The shooting and subsequent chase left many cars wrecked and damaged and, ultimately, the interstate was forced to close temporarily. As you can imagine, this was not a calm situation.
The GBI dispatched their laser scanning team to the site to set-up and scan the area to document the evidence both known and unknown at the time. They also generated 3D photography to further document the area in its entirety.
Using this method, they not only saved time, but were also able to quickly collect the data that would be necessary if the case were to go to trial.
So why use laser scanning to document a scene like this?
First, consider the sheer size of the scene. In this case, the area of study was larger than a football field. Without scanning, investigators would have had to take multiple photographs and make measurements with total stations that shoot one point at a time or worse, measure with 100 foot-long measuring tapes.
This takes much more time, requires more people, and creates much more chance for errors. The errors could be wrong measurements or even missed objects.
When you combine the laser point cloud data with the photographic data, the measurements and the scene become much more intuitive and obvious. You can place the evidence markers by the evidence within the scene and the scanner automatically picks them up.
Instead of making and recording many different angles and distances, you simple put in the points per square foot you want to capture into the scanner and in about 15 minutes, you have a completed scan with photography.
You can look at the scan and very clearly see the markers and measure from any object in the scan to any other object in the scan. So, if you need to know how long a skid mark is, for example, you would just click two points – one at the beginning and one at the end – and the measurement would be instantly generated.
With laser scanning, time at the scene is used to locate and mark the evidence and important points in the scene. All critical measurements can be made offsite after the scene is moved and the traffic is moving again.
Here’s the most important part: If you need information about the scene, but did not know it at the time of the scan, all is not lost! If it exists in the scan, you can make all the measurements you need to document the new (previously unknown) evidence.
More and more, laser scanners are being used to document crime scenes across the country. District attorneys like the scanned data because they can easily view it.
Scanned data is totally objective in that it collects the whole scene. It is easy to put a point down on the ground every square inch so that the coverage of the site is complete. Additionally, the fact that no one has to decide what measurements are made in the field before they release traffic is very important.
Judges like the data because the jury does not have to visit the site to understand the scene. Instead, they can simply view it in 3D on a computer screen without leaving the courtroom.
Laser scanning also saves time and money. Traffic still has to be stopped for an investigation, but if not for laser scanners, it would be stopped longer and there would be less information collected.
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 firstname.lastname@example.org or visit www.landairsurveying.com.