A FIELD METHOD FOR MEASURING THE THERMAL INFRARED EMISSIVITY

In this work, a field method for measuring thermal infrared emissivities is proposed which is based on the box method, initially developed by Buettner and Kern (1965), for laboratory measurements. A theoretical analysis was made of the measurement carried out using the box and a correcting factor to Buettner and Kern's technique has been determined. Buettner and Kern's method has been modified to use radiative temperatures measured with a radiothermometer instead of radiance measurements. The walls of the box used and the cold lid was made of polished aluminium and the hot lid was made of black-painted anodized aluminium and it was heated in the field by solar radiation. With this method measurements of the thermal infrared emissivity of ground and vegetation can be obtained with a relative error not larger than 0.6%.