Luminance measurement for underground mine lighting

Underground mine lighting is critical for the safety of miners and for the ability of miners to perform their jobs. Measuring luminance to determine proper illumination within an underground mine is faced with many challenges because in practice, luminance measurements are affected by the photometer accuracy, measurement method, and condition of the measurement surface. Laboratory experiments and field testing in an underground coal mine were performed at four rib locations in order to quantify various sources of variance, including the variances due to angle offset of the photometer, measurement distance from the coal rib, changing texture of the coal rib, and wetness of the coal. The variations among different locations of coal ribs within the mine were also considered. Results showed a very large variation in the luminance measurements that ranged from a -42.9% luminance change when the coal rib was wetted up to a 76% luminance change when the photometer perpendicularity was offset by 5°. The results indicate that field measurement of luminance is likely impractical given it is affected by multiple factors that are difficult to control in the field.