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A Comparison of Metrology Used in Documenting Shooting Incident Trajectories

Toby Terpstra, Alireza Hashemian, Tilo Voitel, & Jonathyn Priest

Abstract: There are several methods and tools for documenting trajectory rods, but little research exists comparing accuracies of these methods. In this study, three targets were constructed, each having two sheets of ¼ in (.635 cm) plywood separated by a 3½ in (8.89 cm) void. Three shots from varying locations were taken at each of the targets for a total of nine shots. Prior to each shot, muzzle locations were documented with a total station, and afterwards the bullet hole locations were documented with the total station as well as a 3D laser scanner. Trajectory rods were then inserted through the primary and secondary bullet holes in the plywood targets and aligned using centering cones. This study compares the resulting accuracies from six different methods for documenting the trajectory rods. For each method, the resulting horizontal and vertical trajectory angles were compared to the baseline LiDAR mapping of the bullet holes and muzzle locations. A total of 102 measurements were taken with a combined average horizontal angle accuracy of 1.2° and a standard deviation of 0.9°. The average vertical angle accuracy was 0.7° with a standard deviation of 0.5°.


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