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15 April 2008 Runway infrared range concept for EVS
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A major problem in obtaining FAA approval for infrared EVS-based operations under poor-visibility conditions is the lack of correlation between runway visible range and IR attenuation or range. The "IR advantage" in fog, although often substantial, varies greatly as a function of detailed droplet-size distribution. Real-time knowledge of the IR extinction at a given destination is key to reliable operations with lower decision heights. We propose the concept of a Runway Infrared Range (RIRR), to be measured by a ground-based IR transmissometer. Although RVR determination now utilizes single-point scatterometry, the very (Mie) scattering mechanism that often affords a significant IR range advantage necessitates a return to two-point transmissometry. As an adaptation of RVR technology, RIRR will include separate determinations of background-scene and runway/approach lights ranges, respectively. The latter algorithm, known as Allard's Law, will encompass background level, light-settings, visible extinction, and camera performance (usually at short-wave IR). The assumptions and validity of this RIRR parallel those for the traditional RVR. Also, through extended monitoring at a hub, the RIRR may be inexpensively surveyed throughout a fog season, thus predicting the economic benefits of IR-based EVS for that site.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
J. Richard Kerr "Runway infrared range concept for EVS", Proc. SPIE 6957, Enhanced and Synthetic Vision 2008, 695702 (15 April 2008);

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