§ 25.2. Definitions.

Beacon. A light with one or more beams directed into the atmosphere or directed at one or more points not on the same property as the light source; also any light system with one or more beams that rotate or move.

Cutoff. A luminaire light distribution where the emission does not exceed 2.5 percent of the lamp lumens at an angle of 90 degrees above nadir, and does not exceed ten percent at a vertical angle of 80 degrees above nadir. These emission values apply to all lateral angles around the installed luminaire.

Footcandle. A unit of measure for illuminance on a surface that is everywhere one foot from a point source of light of one candle, and equal to one lumen per square foot of area.

Full cutoff. A luminaire light distribution where zero emission occurs at all angles of 90 degrees or greater above nadir, and the emission does not exceed ten percent of total lamp lumens at a vertical angle or 80 degrees above nadir. These emission values apply to all lateral angles around the installed luminaire.

Glare. The sensation produced within the visual field by luminance that is sufficiently greater than the luminance to which the eyes are adapted, causing annoyance, discomfort, or loss in visual performance and visibility.

Illuminance. The quantity of light arriving at a surface divided by the area of the illuminated surface, measured in footcandles. Horizontal illuminance applies to a horizontal surface; vertical illuminance applies to a vertical surface. Average illuminance is the level of illuminance over an entire illuminated target area. Maximum illuminance is the highest level of illuminance on any point within the entire area; minimum illuminance is the lowest level of illuminance on any point within the entire area.

Illuminance levels. All illuminance levels and foot candles noted in this ordinance mean the maintained illuminance levels: the illuminance levels occurring just prior to lamp replacement and luminaire cleaning. The average illuminance level applies to an entire illuminated target area. Minimum and maximum illuminance levels apply to small areas within the entire illuminated target area. Unless otherwise noted, illuminance levels refer to horizontal illuminance levels.

Lamp. The component of an outdoor luminaire that produces light.

Light trespass. Unwanted light emitted beyond the boundaries of the property on which the luminaire is located, detrimentally affecting residents, vehicle operators and pedestrians, the natural environment, and astronomical observations.

Luminaire (light fixture). A complete fixed or movable lighting unit consisting of a lamp or lamps and ballasting (when applicable) together with the parts designed to distribute the light, to position and protect the lamps, and to connect the lamps to the power supply.

Person. Any individual, tenant, lessee, owner, or any commercial entity, including, but not limited to, a firm, business, partnership, association, joint venture, corporation, or organization, whether commercial, religious, fraternal, social or otherwise, or any agent thereof.

Roadway lighting. Lighting that is specifically intended to illuminate roadways for automobiles, excluding the lighting intended to illuminate roadways only for pedestrians.

Security lighting. Continuous illumination of nonroadway territory when there is no minimal nighttime activity by authorized individuals.

Semi-cutoff. A luminaire light distribution where the emission does not numerically exceed five percent of the total at an angle of 90 degrees above nadir, and 20 percent at a vertical angle of 80 degrees above nadir. These values apply to all lateral angles around the installed luminaire.

Shielded. provided with internal and/or external shields, top and side visors, hoods, and internal louvers to limit glare, sky glow, and light trespass caused by emission from luminaires.

Sky glow. The brightening of the nighttime atmosphere by light emitted above the horizontal plane and by light reflected upward from illuminated surfaces, which reduces the visibility of astronomical objects.

Uniformity ratio. A higher level of illumination in relation to a lower level of illumination within a given target area. A value for either the maximum-to-minimum ratio or the average-to-minimum ratio may be required. For example, if the average-to-minimum uniformity ratio is 4:1 for the given target area, the lowest level of illuminance is no less than one divided by four (25 percent) of the average level of illuminance.

(Ord. No. 2001-009, § 2, 7-10-01)