Minimum Vertical Illuminance: 2 lux (0.2 fc) Using these guidelines, measurements should be taken at a 1.0-meter (~3-foot) elevation with the light meter pointing up the slope. For competition and event lighting , higher levels are required, as outlined in the Technical Elements for Event Lighting subsection. These levels ensure safe skiing and riding while minimizing energy use and glare, aligning with sustainability goals. Understand that half a footcandle is a very low level; yet, snow’s unique reflectivity provides sufficient visual acuity at these levels using a white light color temperature (Kelvin temperature). Uniformity… meaning consistent light levels from pole-to-pole, becomes a more important criteria to avoid eye adjustments from light-to-dark between poles. 2. Design Considerations Effective slope lighting must address unique challenges of snow-covered environments, including variable weather, reflective surfaces, and slope topography. The following considerations ensure functionality and sustainability: • Illuminance Uniformity : A uniformity ratio (average to minimum illuminance) of 3:1 or less is recommended to avoid overly dark or bright spots that could disorient skiers/riders. Semi-directional lighting enhances visibility by providing shading and modeling, helping skiers discern terrain features. Excessive uniformity can flatten perception, reducing safety. • Weather Conditions: In foggy or snowy conditions, increase the minimum vertical illuminance by 3 lux (0.3 fc) to compensate for light scattering and reduced visibility. This adjustment maintains safety without excessive energy consumption. • Field Measurements : Measure light levels during clear weather and a new moon with typical snow cover to account for snow’s reflectivity, which can amplify illumination. This ensures accurate design and minimizes over-lighting. • Luminaire Aiming: NSAA recommendations are for aiming luminaires downhill, aligning with the skier’s direction of travel. This assumes high intensity lighting sources such as high-intensity discharge (HID) lamps and LEDs. Lighting specifically designed for slope applications, like magnetic induction fixtures that can be aimed uphill to remove forward shadowing, came after NSAA recommendations were originally introduced. This is particularly important for competition racing, freestyle, halfpipe, and jumps. (See specific sections on these applications.) Adjustments must be made using LEDs for slope curvature and gradient to minimize "white-out" (overly bright, flat lighting) and glare. Proper aiming enhances terrain visibility and reduces light pollution. There is technology specifically designed for slope illumination based upon low-glare magnetic
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