NCJ Number
220045
Journal
Law Enforcement Technology Volume: 34 Issue: 8 Dated: August 2007 Pages: 34,36,38,46
Date Published
August 2007
Length
11 pages
Annotation
This article describes the equipment features, benefits, and costs of three types of methods for traffic crash-scene measurement: manual measurement, electronic measurement, and photogrammetry.
Abstract
Manual measurement is the simplest method for measuring significant distances at crash scenes. This article describes the various types of tape that can be used, including a 300-foot tape measure and the Rolatape, which is a wheeled measuring device with a digital counter that quickly and accurately measures distance for crash reports (price begins at $99). Most law enforcement agencies, however, use a combination of electronic accident-scene mapping tools or a specific kind of mapping device. Among the chief electronic mapping methods are total stations, laser measurement systems, GPS (global positioning system), and laser scanners. Total stations combine electronic distance measuring (a cooperative laser to measure distance) and a theodolite for measuring angles. The technology of this system is described in detail. Laser measuring devices are increasingly being used to measure crash scenes. The Laser Technology, Inc., (LTI) laser systems combine reflectorless laser technology and electronic data collection. Although not a widely used method, GPS technology can be used to produce a graphical representation of a crash scene that is accurate to less than 2 centimeters. This system requires only one person for its operation. Photogrammetry, a third technique for measuring crash scenes, obtains three-dimensional measurements from photographs. It typically involves using a digital camera and close-range photogrammetry software. It is a one-person operation and takes a short time to complete at a crash scene. Since the cost of some of the described mapping technology is beyond the capability of some agencies, grant sources are discussed.