Illuminance Uniformity of Outdoor Sports Lighting

Abstract This paper analyzes the illuminance uniformity of 30 outdoor sports fields at various points in their service lives. The study was limited to the fields that employ 1500 W metal halide lamps with a rated life of 3000 hours. The sample was comprised of 12 soccer fields, 14 baseball fields, and 4 softball fields, all of which are owned and maintained by municipal parks and recreation departments. Five uniformity indices were computed for both measured illuminance and initial design calculations: maximum to minimum ratio (Max:Min), maximum to average ratio (Max:Ave), average to minimum ratio (Ave: Min), coefficient of variation (CV), and uniformity gradient (UG). Measured uniformity was rarely as good as the uniformity predicted by the design calculations. The uniformity of the baseball and softball fields was better with hours-of-use, with infields and outfields exhibiting similar trends. Max:Min, UG, and CV indices, as well as the illuminance of the transition area between infield and outfield, are suggested as key evaluation parameters. Group vs. spot lamp replacement, as-built vs. as-designed, dirt accumulation, and out-gassing are factors that contribute to sports lighting uniformity.