EXPLORING NEW 3D TECHNOLOGY - PART 2

Continuing our discussion from our February 2023 issue, ATA Associates conducted a mock investigation on a road in Webster, Texas.

The goal of the test was to compare technology error margins to determine if newer technology matches or exceeds already court qualified technology. Conditions of a planned incident site were established to set up a controlled environment in which measurement variables were all known. Extensive physical measurements were taken to compare subsequent measurements made using technology.

Officers from Harris County Constable Precinct 8 and Webster Police Department created a safety barricade with their vehicles at each end of a 700 ft road to prevent vehicles from entering the test area, and two test scenarios were conducted:

(1.) An accident reconstructionist documents the vehicles at the site.

(2.) An accident reconstructionist documents the site and then documents the vehicles at a separate location.

The following chart lists the multiple types of technology used to document the site and each vehicle. The traditional technology is established, court-qualified technology commonly used in the industry already. New technology indicates equipment or software that has become available in the past five years.

With Vehicles On-Site (Scenario 1)

Each piece of equipment was given one hour to make on-scene adjustments and to complete its assigned purpose. We positioned the box truck and F-150 on the road according to markings we had previously painted on the road and the FARO scanner was positioned to scan the vehicles on site at six different scan points. The site with vehicles was then photographed with the iPhone 14 Pro Max and a Nikon Coolpix B500 camera.

While the FARO was scanning, we flew the drone overhead to photograph the site aerially and photographed the vehicles for Context Capture. Using both the iPhone 14 Pro Max and Nikon Coolpix B500 camera, we photographed the vehicles from three heights (approximately 2 ft, 4 ft and 6 ft) then moved about 2 ft laterally and repeated the process until we completely circled the vehicle.

After photography and FARO scanning was completed, we subsequently scanned the vehicles and site with the iPhone applications.

Without Vehicles On-Site (Scenario 2)

Once all the vehicles were photographed and scanned at the site, we moved both the F-150 and box truck off-site to create a more realistic scenario. Most accident reconstructionists do not have the opportunity to view the vehicles at the accident site, so documentation of the individual components was completed as it would be done independently in a post-incident setting. The site was photographed with an iPhone 14 Pro Max, a Nikon Coolpix B500 Camera and a DJI Mavic 3 Drone. Other site documentation used a V-Box Data Logger, a Spectra survey system and a Moasure ONE survey system.

Multiple drive through passes were made while recording the site layout with a VBox Data Logger, whose data would be used to verify site surveys executed with the Spectra and Moasure ONE survey systems.

In theory, if every scan and the subsequent processing of that scan was perfect, then every 3D graphic would overlay without error. This graphical analysis is supported by numerical analysis in which measurements taken from the actual site and vehicles were compared in a 3-dimensional (X, Y, Z) format to measurements taken from the 3D renderings. Any differences that were found between the physical measurements and those in the 3D renderings were determined to be based on source accuracy.

In conclusion, we have determined that all forms of technology we evaluated have been verified for accuracy and have been proven to be successful. In addition, all technologies must be understood and worked within its specific parameters and idiosyncrasies. If properly applied in the right environment, all the tested technologies and tools can be useful to a crash investigator when trying to understand what occurred during a crash event.

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LITHIUM BATTERIES - UNIQUE FIRE CHARACTERISTICS PART 1

By Steven D. Emerson, PhD, PE
Emerson Technical Analysis, LLC

Lithium batteries are found just about everywhere in our lives, from mobile phones to flashlights to EV automobiles. Large grid-scale battery storage is touted as the answer to non-dispatchable, renewable power sources such as wind turbines and solar arrays. These batteries are lightweight, packed with energy, rechargeable and convenient, and they will become even more widespread in the future.

However, lithium batteries can burst into flame if mishandled. It is not unusual to see reported fires of electric vehicles or battery-powered buses. New York City’s Chief Fire Marshall reported over 200 fires in 2022 alone from micro-mobility devices. On the other end of the size spectrum, large demonstration units of grid-scale power storage have been plagued with destructive fires. Because of their extraordinary intensity, these fires often propagate to nearby vehicles or buildings, and they are also unusually difficult to extinguish. What makes them so unique?

BATTERY DESIGN

The most common lithium battery today is the lithium-ion battery. The figure below depicts its general architecture, in both charging and discharging modes.

Such batteries can best be described as electrochemical cells. This suggests that both physics and chemistry are involved: physics to govern electricity flow within the battery case and around external circuits; chemistry because of the reversible chemical reactions that store energy within the cell.

Component parts include:

"Anode" (negative charge) and "Cathode" (positive charge) on opposite ends of the battery. These metal connections serve as collectors of electrical current from internal reactions, and as contacts to the external world.

"Electrolyte" is the liquid solution that allows lithium ions (Li+) to diffuse as they migrate from anode (where they have given up an electron) toward the cathode during discharge, and in the opposite direction upon charging. Electrolyte commonly contains dissolved lithium hexafluorophosphate (LiPF6) salt in organic carbonates.

"Separator" is a thin insulating film, inserted between the anode and cathode to prevent internal short circuiting. Lithium ions diffuse through the microporous structure.

"Lithium Metal Oxides" (on cathode side) and "Lithium Carbon Compounds" (on anode side) provide lithium ions within the battery electrolyte itself.

(...to be continued next issue)

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