像元二分模型VFC：可用于基于植被指数和像元二分模型的植被覆盖度因子提取方法以及土地利用因子提取方法,通过叠置分析实现土壤侵蚀信息提取等等(Two pixel VFC model: can be used for extraction of vegetation index and two sub pixel model based on vegetation coverage factor and land use factor ex