An Automatic Retrieval Method for Artificial Terrace Based on Illumination Model of DEM Shading
As one of the most typical artificial landforms in loess plateau of China, artificial terraces have important value in agricultural production as well as soil and water conservation. The previous studies on terrace automatic extraction only focused on their boundaries and failed to achieve effective and automatic extraction of their ridge lines. In this study, a quick extraction method of terraces based on illumination and shading simulation of DEM is proposed. Firstly, illumination and shading simulation in four-direction is carried out using 1 m digital elevation model (DEM) generated by Unmanned Aerial Vehicle (UAV) technology and average value of four simulations was calculated. Secondly, the image of the mean value is binarized into a logistic image using a proper threshold. Also, valley and other non-terraced areas were masked off. Finally, terrace ridge lines were obtained by automatic vectorization of the logistic image. Some broken lines were filtered by a proper length threshold to improve the extraction precision. Taken Wangdonggou watershed, Changwu County, Shaanxi Province as the study area, the experiment results showed that this method had a preferable extraction accuracy of 89.09%. Furthermore, the parameters involved in this method were also discussed. The results showed that if we take two orthogonal symmetric direction angles as the direction angles, arctangent value of the slope of terrace ridges as the altitude angle, an empirical formula (t=180-σ) was used to calculate the threshold value of the logistic image, the quick automatic extraction of artificial terraces of loess plateau can be achieved.
DEMartificial terraceillumination of the shadingloess plateauGIS
NETL
NSTL
万方数据
维普
