Topographic and spatial-scaling effects on the sunlit time of the different terrains

A revised sunlit time computation model based on the DEM data in rough terrain has been developed in this paper. In order to improve the accuracy of the calculation, an earth curvature revising factor Q was carried out in the model base on the former researchers. In this study, 6 sample areas of representative terrain types within P. R. China were selected and their spatial distributions of sunlit time on the vernal and autumnal equinoxes, the Summer Solstice and midwinter day in two different resolutions (500 m and 1000 m) were calculated using the model developed in the study. In this paper, the calculated results of sunlit time using revised and unrevised models were finely compared and the topographic and spatial-scaling effects on the sunlit time were deeply analyzed through two aspects: the different terrain types and different spatial scales of the original DEM data. The changing rules of sunlit time according to the geomorphology and spatial scale were found out and very significative in applications