At five to ten feet from the edge, we are considering primarily canopy luminaires. Since the UIF values for the analyzed luminaires range from about 0.4 to 0.1, the practical value of 0.25 is adopted for this range. Luminaires will rarely be farther than twenty feet from the edge, since few canopies are larger than about 40 or 50 feet across, and the luminaire will begin to approach the other edge. Using the factors of 1.0 for pole-mounted luminaires and luminaires mounted within five feet from the edge of an overhang or canopy, 0.25 for luminaires 5 to 10 feet from the edge, and 0.1 for those 10 feet or more from the edge, lighting is included toward the lumens per acre caps in approximate proportion to uplight impacts, without requiring an involved analysis for each installation. Since we define the UIF as the ratio between the uplight for the canopy-mounted luminaire and the uplight for the same luminaire with no canopy present, the reflectance of the ground surface cancels and can be ignored.
All designs assume luminaire heights of fifteen feet.
To determine the area integral, the average illuminance value is multiplied by the square footage of the specified area. For the pole-mounted configuration, the appropriate area is chosen to be the rectangular area that includes all points with illuminance 0.01 footcandle and above. To determine the UIF for a luminaire mounted at the canopy edge, the appropriate area is just half of the area for the pole-mounted configuration, with the dividing line running through the point directly below the luminaire. For a luminaire mounted two feet from the canopy edge, the appropriate area begins at the point two feet from the point directly below the luminaire, and so forth. This approach assumes that no light escapes upward from the ends or far side of the canopy.