Evaluation of Navigational Range Lighting Parameters for Daytime and Nighttime Conditions
COAST GUARD RESEARCH AND DEVELOPMENT CENTER GROTON CT
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The purpose of this study was to evaluate, using experimental methods under actual field conditions, parameters and relationships used by the U.S. Coast Guard USCG in the design of daytime and nighttime lighted parallax navigational ranges. In one experiment, thresholds of minimal separability, in terms of the angle at the observers eye subtended by two lights, were measured for various light intensity combinations under both daytime and nighttime conditions. In a separate experiment, thresholds for detection of lights under daytime conditions were determined. Results suggest that the current process used by the USCG to prevent blurring together of the two lights while minimizing required tower heights for nighttime ranges is valid. For the daytime results, the design guidelines for minimum tower height separations, for the illuminance levels evaluated, are adequate for illuminance ratios less than 1.61. Results for the second experiment showed that the present USCG practice of using a factor of 1000 to convert the illuminance level specified for nighttime range light signals to a level adequate for daytime use is also valid. This Validation of current practices allows the USCG continued significant cost savings in the construction of towers used for navigational ranges.
- Navigation and Guidance