Citation

Reust TJ. Collision 2011; 6(1): 96-98.

Copyright

(Copyright © 2011, Collision Publishing)

DOI

unavailable

PMID

unavailable

Abstract

The global positioning system (GPS) navigation units commonly used by consumers for route guidance can record and store information. This information potentially can be downloaded and used to evaluate accident events. This study tests two of consumer GPS units. The available information from these units includes date, time, GPS coordinates, elevation, compass heading angle, travel distance and vehicle speed. Different price ranges and ages of units were compared to evaluate their sampling rates. The cost of the unit did not appear to affect the sample rate, but older units were found to sample less often than more recent units. Archive files are stored in some units. Testing was also conducted to evaluate the accuracy of the distance between data points. The results of this testing indicated that leg length (the distance between two successive data points) distances between 20-30 ft have an accuracy of approximately 3.3 to 10%. Distances between 1000 ft and less than 0.1 mi have an accuracy of about 1.7% and distances given in tenths of a mile have an accuracy of approximately 2.3%. Testing the accuracy of both single point GPS coordinates and continuous strings of coordinates was done by documenting the position of the vehicle at the beginning or end of a test and documenting the path position of the vehicle on the roadway. Results showed that the coordinate's positions may vary over time by as much as 8 ft. A translational shift (i.e., shifting the entire string without rotation) can be used to correct variations in a continuous string of coordinates.