Tuesday, December 20, 2011
Similar to the technology aiding speed enforcement, the tools used for crash reconstruction also aim to improve safety for officers and motorists.
Total stations, widely used by crash scene investigators, are one of several options for scene mapping. They measure horizontal and vertical angles and distance, and calculate the slope distance and the elevation of a point in 3D space. Most frequently used are ‘reflectorless’ total stations, which can measure a slope distance without a prism, and ‘robotic’ total stations, which are operated via remote control.
The Sokkia Prismless Mapper function for its reflectorless and robotic total stations is designed specifically for law enforcement uses. The Prismless Mapper’s extremely narrow, visible red laser pinpoints and accurately measures difficult positions such as small objects, edges of walls or targets located at a steep angle. It also measures through obstacles like chain-link fences and trees.
Neal Trantham, owner of Nebraska Accident Reconstruction, uses a Sokkia SET 630R reflectorless total station when crash scenes involve heavy traffic or occur at night. “At night, I can see the laser pointer (Prismless Mapper) on my Sokkia total station without sighting through the device, which saves a lot of time as I stand safely out of traffic,” says Trantham.
When speed of mapping is essential, Trantham recommends using a robotic total station. In this case, he uses a Sokkia SRX Robotic Total Station, which makes crash scene mapping a one-person operation, allowing other crash reconstructionists to take photographs, examine vehicular evidence and coordinate other investigation details.
“Clearing the scene quickly results in less disruption to the general public, but most importantly reduces the chance of secondary crashes occurring,” Trantham says.
An alternative scene mapping technology is a portable laser system that combines reflectorless technology and electronic data collection. Sgt. Richard Taylor of the Douglas County (Colo.) Sheriff’s Office Traffic Unit uses the LTI UltraLyte 200 Series mapping system for crash scene documentation. The UltraLyte accomplishes speed enforcement and crash reconstruction. Taylor uses it with LTI’s MapStar Angle Encoder for 3D mapping. The tools allow him to quickly and accurately document a scene.
Before the traffic unit began using the LTI tools, it documented crash scenes via baseline measurement (a crash scene measuring technique where the location of evidence is measured linearly from a fixed point such as a utility pole along the edge of the road) and hand-drawn sketches.
“When you have to take baseline measurements, you’re all over the road taking measurements,” says Taylor. “With the laser system, you set up at one location and that equipment doesn’t have to move. You just have one person in the field with a prism pole marking your evidence.”
The result: “You have fewer officers out in the roadway. With this equipment, it’s so much faster to clear the scene.”