A new video-camera-based visiometer system

We provide a novel design of atmosphere visibility measurement system with the contrast principle used in the naked eye visibility observation. The new digital photography visiometer system (DPVS), composed of a CCD camera and two identical targets, utilizes the contrast of dual targets to measure the visibility. Two operational modes are designed to enable the DPVS to accommodate the lighting conditions of the day and night. Two passive targets, black bodies, are employed for daytime visibility measurement, and two active lights, LED panels, are utilized for nighttime. The mathematical models of the dual targets for both daytime and nighttime are developed, and the sensitivity analysis shows the requirements of the hardware to achieve desired accuracy. The design of the target including the blackbody and the LED panel is briefly discussed, and the temperature dependence and stability of the LED panels are measured experimentally. Finally, the DPVS is compared with two commercial visibility devices, a forward scatter meter and a transmission meter for field validation. A 5-day comparative experiment shows that the measurements of the DPVS generally well agree with those of the transmissometer and the forward scatter meter for visibility up to 15 km, and the relative bias of 87% of the DPVS measurements lies between −0.2 and 0.2.