基于“北京一号”小卫星数据的密云水库流域植被覆盖度估算方法比较

“北京一号”小卫星（BJ-1）是一颗拥有高时频、覆盖宽度大等优势的对地观测小卫星。运用BJ-1遥感数据，以密云水库流域为研究区域，通过NDVI像元二分法、三波段梯度差法估算其植被覆盖度，并尝试利用重归一化植被指数（RDVI）法进行植被覆盖度估算。通过对3种方法估算结果的比较发现：RDVI法的估算结果与实测值的吻合度较高，而三波段梯度差法则出现较大误差，NDVI像元二分法的估算结果精度居中。结果表明：运用BJ-1数据，采用RDVI法可以有效地进行连续的、大范围的植被覆盖度估算。

Comparisions of Estimating Methods of Vegetation Fraction Based on “BJ-1” Microsatellite Imagery

BJ-1 Microsatellite is the advanced member of the Disaster Monitoring Constellation(DMC) with two powerful cameras.One camera can monitor coverage of 600km by 600km,while the other developed by Sira,can capture images of a 24km wide strip of ground with a resolution of four metres.Vegetation fraction coverage is an important parameter for describing vegetation quality and indicating ecosystem change.In this study,BJ-1 images were used to detect and analyze the vegetation fractional coverage in the basin of Miyun reservoir.Based on the analysis of the current methods,this paper uses three kinds of methods,including Dimidiate Pixel Model from Normalized Difference Vegetation Index(NDVI),3-bands Grads Difference Method and a new method based on Renormalized Difference Vegetation index(RDVI).According to the experimentation,the estimating values by RDVI method has a better relationship with the verification values,while the other two methods appeared a bigger difference with the ground true values.On the whole,RDVI method shows good characteristics and can be used in estimating of vegetation fraction in conjunction with BJ-1 satellite image data.