Visibility monitoring using mobile application

Abstract

Visibility is clarity with which the distant objects are perceived in the atmosphere with the naked eye. Visibility monitoring is an important concern in health, environment and transport safety context. Quantitative measures of visibility are increasingly becoming important in various areas as they are representative of the particles present in the environment that causes degradation of the visibility. Existing techniques of visibility estimation employ human observers, optical instruments, chemical sensors or combination of some of them. These techniques suffer from poor spatial and temporal resolution, high cost of installation and maintenance, need of specialized personnel, continuous power supply requirement and difficulty in portability. We propose a smart phone-based visibility monitoring system which estimates air visibility/quality in terms of a quantitative measure: Turbidity. In principle, the application calculates turbidity as difference of intensity of captured sky image and analytical value of sky luminance obtained by implementing Perez model. The estimated turbidity tagged with date, time, location, solar position and luminance is sent to the backend server generating consolidated database for mapping of turbidity and generating various analytical reports. The application can easily be deployed to be used by large number of people facilitating citizen science. The results from application were validated against the observations from SAFAR India application at different stations in Ahmedabad, dates and under variable weather conditions.