Evaluation of Sample Taxicab Security Cameras

摘要

Background: Taxicab drivers have high homicide rates compared to all worker occupations. To help taxi fleets select effective taxicab security cameras, this project tested eight sample taxicab security cameras for determining their photographic quality which correlated to the effectiveness of in-taxicab facial identification. Methods: Five photographic quality metric thresholds: 1) resolution, 2) highlight dynamic range, 3) shadow dynamic range, 4) lens distortion, and 5) shutter speed, were employed to evaluate the photographic quality of the sample cameras. Waterproof tests and fire-resistive tests on recording memory cards were conducted to determine the memory card survivability in water and simulated fire. Results: The Full-HD (1920 × 1080 pixels), HD (1280 × 720 pixels) and dual-lens VGA (2 × 640 × 480 pixels with wide-angle and telephoto lenses) cameras performed well in resolution tests in daylight conditions. The resolution of a single-lens VGA (640 × 480 pixels) camera did not meet the resolution minimum requirements. All of the recording memory cards passed the five-meter/72-hour waterproof test. A fire resistant chamber made with one fire insulation material could protect a single memory card at 538 lang="EN-US" style="font-size:11.5pt;font-family:;" "=""> style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°C/1000 style="font-size:11.5pt;font-family:宋体;"> style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">° style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">F lang="EN-US" style="font-size:11.5pt;font-family:;" "=""> for a five-minute simulated fire test. Conclusions: Single-lens VGA-resolution (640 × 480 pixels) cameras are not suggested for use as security cameras in taxicabs with two or more rows of seats. The recording memory cards can survive 5-meter/72-hour waterproof tests. The memory card chamber built with an existing heat insulation material can protect an individual memory card during 538 lang="EN-US" style="font-size:11.5pt;font-family:;" "=""> style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">°C?(1000 style="font-size:11.5pt;font-family:宋体;"> style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">° style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">F lang="EN-US" style="font-size:11.5pt;font-family:;" "="">)/5-minute fire resistance oven-test.