When it comes to the forensic mapping of a motor vehicle crash or crime scene, one of the main rules is the K.I.S.S. (Keep It Simple, Sarge!) principle. You also need to be accurate in documenting the scene. I have found over the years, Laser Tech (LTI) has been able to, and still does, meet these primary needs.
The advent of drones, 3D scanners, and other types of modernized automated systems has many investigators swept up. No doubt, these advanced tools are powerful and useful in their own ways. Still, when it comes to the vast majority of crashes that require police to reconstruct the scene, a lot of these systems are overkill and tend to be cost-prohibitive.
Considering the final product you want to produce is the first step for an at-scene investigator. This will dictate what sorts of mapping equipment you should use. You’ll draw a basic flat 2D map of the scene to-scale in almost every instance. You can print this out, touch it, and put it in the case folder; believe it or not, many police agencies still use old-school case folders!
2D diagrams also enable crash reconstructionists to produce CAD program sequences in time, distance, and momentum, with all necessary diagrams ready for printing. These 2D diagrams are also very useful in court, especially when they’re enlarged or used in PowerPoint®. Some newer systems, advanced as they are, cannot support these basic needs.
Here’s a common topic of discussion: What is the measurement accuracy of this forensic mapping system? Is it more accurate than my other system?
Laser Tech’s crash reconstruction mapping kits can achieve a distance accuracy of ±1.6 inches, with an inclination and azimuth accuracy of ±0.1 degrees. Some will say that’s too high of a tolerance for distance. Others are quite comfortable with it. Before you decide, let’s take a closer look at accuracy when dealing with crash investigation mapping.
Were the tape measures certified? Did the fiberglass tapes stretch? Was it really a right angle for the coordinate measurement?
How long was that skid mark? I saw two more feet than you did! Do we use the longest skid or the shortest skid? Or, do we add and average the length of the skids for our speed calculations?
How wide was the pencil point? Six inches, one foot? So much for accuracy they taught us in class!
Are you holding your prism pole perfectly plum on the spot? What is your drone’s lens-to-sensor aspect ratio? What about the angle of view and image distortion?
We dismissed photogrammetry years ago as being so inaccurate that it couldn’t stand up in court! Even scanners don’t “get” everything. The “spot” requires enhancement, which then threatens to change its location, height, and even size.
None of this equipment is accurate enough to truly measure a critical speed yaw mark on a road surface.
You still have to complete this by hand. Investigators must take measurements on at least two portions of the yaw to record the decreasing radius of the arc for any speed calculations. Let’s not forget the sensitivity analysis! One must show the range of high and low speeds based on all the variables involved.
If the curb line is half an inch off, did it have anything to do with the crash? Nope! Remember, we draw our diagrams to a scale. It’s not a scaled diagram of the crash.
One of the significant advantages of a Laser Tech mapping system is that you are in control of the entire process from start to finish. You select the location to set up the station, you decide what evidence to document, and most importantly, you control the number of points to measure.
If you need 20 points, you shoot 20 points. If you need 500 points, you shoot 500 points. The system does not decide how many points to map or which points to map. With Laser Tech mapping solutions, you make all the decisions.
With Laser Tech’s LaserSoft® QuickMap 3D® as your data collection application, you can visualize the scene developing before your very eyes. You can even find distances between points and zoom into areas of the scene. Let’s also not forget that you can fire the laser wirelessly from the tablet! You are not relying on an automatic system. You know exactly what your LTI crash investigation mapping system is recording.
Adding to the problem are the many operational limitations and requirements of some newer systems. In plenty of cases, the operator has no control over this. Yes, every system has limitations; but in my experience, the LTI crash reconstruction mapping systems have much fewer limitations than drones or scanners.
Picture a crash or crime scene that requires crash investigation mapping. You are the investigating officer.
One of the first things you need to do is determine what evidence requires documentation. This dictates how large the area, or scene, will be. Imagine that you’re planning to utilize an LTI forensic mapping system. Your next step is to select a safe location to set up the station. ideally, you want to pick a spot where all evidence points are visible. If one location won’t do the trick, you can easily move, or traverse, your system as many times as the scene requires.
Your LTI mapping station consists of a survey tripod, tribrach, a MapStar® TruAngle® encoder, either a TruPulse 200X® or TruSpeed SXb® laser rangefinder, and a tablet with QuickMap 3D running. Setting up the station takes you about 5 minutes. You can cut that down even further once you become more familiar with the process.
You start shooting the evidence points in one of two ways: you can either shoot the laser to a prism or you can shoot directly to the point or object itself. If shooting to a prism, you’ll need a teammate to hold the prism pole at each evidence point. With this 2D mapping system, there is no need for you to register the target’s height. Your Laser Tech system “flattens” the scene.
When you “fire” the laser, your LTI crash investigation mapping system measures azimuth, inclination, and slope distance all at once. This data displays as a dot, with a sequential number and note, in an X-Y grid within your QuickMap 3D app. This makes it easy to see each evidence point you’ve recorded in the scene. As you record the points, you even have the ability to connect them with a line or arc. This is just the tip of the iceberg of features in QuickMap 3D!
You finish shooting the scene. Now, you can save your work in seven different formats and email them to the required addresses. Did I mention that you don’t need any cables? You can fire the laser and transfer the data over Bluetooth™ at a range of over 200 feet!
You’re back at the office. You download the files of the scene from your email and import the appropriate file(s) into your CAD program. From here, you basically connect the dots to draw the scene. You can add features as needed and the diagram can be as straightforward or as elaborate as you want to make it. Sometimes the aforementioned K.I.S.S. principle works here too.
Numerous CAD programs are out there, and the files you’ve created in QuickMap 3D® will open in all of them. I have found FARO® Zone 2D to be a very user-friendly program. It comes with more features than you might expect at its selling price! It also does not require a high-end gaming computer to run the software and will run on almost any modern computer or laptop.
I discussed dealing with a crash scene, but I would like to mention Laser Tech’s TruPoint 300® forensic mapping system briefly. It is a smaller total station system that can map both indoor and outdoor scenes. It uses the same tablets and QuickMap 3D software as the mapping systems discussed above. You get measurements by placing the red dot aiming feature at the evidence point. Just like other Laser Tech crash reconstruction mapping systems, each shot records the same three types of measurements outlined above. It also measures in 2D or 3D.
One of the side benefits of this system is an accuracy of ±1 mm (±0.04 inches) for distance measurements. This makes it a perfect tool for measuring the crush-profile of a vehicle.
Several goals present themselves when you investigate a crash scene. One of them is minimizing roadway closure time, which makes life easier for everyone involved. Laser Tech’s crash investigation mapping systems have the capability to quickly and easily produce the data to make a “basic” map. Still, they can produce detailed, extensive 3D measurements to achieve more than basic maps. Just remember, K.I.S.S.
Find out more about how Laser Tech solutions and other useful forensic mapping tools for crash investigation work together to keep your department's toolkit versatile and ready for all situations.Pros and Cons of 7 Crash Reconstruction Tools