Evaluation of the MODIS and ASTER Emissivity Products Using Insitu Measurements

Surface Emissivity mapping is a need in thermal remote sensing. Having accurate values of emissivity, one can determine surface temperature more accurate where this temperature can be used in environmental and climatic studies as well as in weather forecasting models. Due to the importance of surface emissivity and the accuracy in their estimation, assessment of the accuracy of MODIS and ASTER emissivity products have been considered in this work. For this, insitu measured values as well as laboratory values of emissivity from 6 different regions in United States of America, whom were extracted from the results of other researchers have used. In this work, TES method was deployed for calculation of ASTER emissivity values where MODIS emissivity values were extracted from 041 and 005 versions. Then, their differences with insitu measured values were calculated and their accuracies were compared with values extracted from bands 8.5 and 11m for concurrent images of these two sensors. The results of concurrent values of two sensors show that ASTER can produce 4.6% more accurate emissivity values in 8.5m band compared to MODIS’s. Also in 11m band, for all regions on the average ASTER has 0.7% accuracy compared to ground values where this for MODIS is 1.2%. It is found that the error for MODIS extracted emissivity values of low emissivity surface covers increases. on the overall, ASTER emissivity values are more accurate compared to MODIS values. It is recommended that this results be taken in to account when using MODIS emissivity products as input in meteorological models as well as those application where accurate emissivity values is needed.