Snow covered surfaces show enormous variations in time and consequently need to be monitored using images with relatively high temporal resolution. For this MODIS sensor on board of Terra/Aqua is suitable. Different parameters affect the accuracy of Snow

Document Type : مروری

Abstract

Snow covered surfaces show enormous variations in time and consequently need to be monitored using images with relatively high temporal resolution. For this MODIS sensor on board of Terra/Aqua is suitable. Different parameters affect the accuracy of Snow Covered Surface estimation (SCS) where the surface topography (slope and aspect) is one of them. The low spatial resolution of MODIS images and presence of mixed pixels causes a decrease in precise SCS estimation using these images. In this work it is tried to assess the MODIS SCS estimation by comparison with moderate spatial resolution sensors such as ASTER on board of the same platforms. In this work the NDSI index of MODIS and ASTER for slopes between 20 to 50 percent were compared and two models of MODMASTER and MODFASTER for improvement of MODIS accuracy for SCS estimation is produced. The results of MODMASTER show a correlation(R) of about 88% and a RMSE of about 0.047 with the equivalent ASTER snow index. The MODFASTER which is based on estimation of the snow fraction in pixels showed a correlation of about 87% and RMSE of about 0.09 with the equivalent ASTER calculated snow fractions. Finally the results were compared with the works of previous workers and show some improvements.

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