面向对象的天然绿洲与人工绿洲区分

以地处河西走廊东端、石羊河下游的民勤县湖区绿洲为例，以Landsat 8 OLI影像为数据源，从天然绿洲和人工绿洲的基本概念出发，在影像数据预处理、多尺度分割的基础上，综合考虑光谱、纹理、形状、上下文等信息，引入NDVI、最大化差异、紧致度、形状指数和空间邻接关系等多个特征，构建规则集进行天然绿洲和人工绿洲的区分，并将区分结果与基于最大似然法监督分类的绿洲区分结果进行比较分析。结果表明：使用面向对象的影像分析方法区分天然绿洲和人工绿洲的总体精度达到了91.75%，Kappa系数为0.65；较之面向像元的最大似然法监督分类结果，总体精度提高了10.40%，Kappa系数提高了0.13，其中人工绿洲条件Kappa系数提高了0.19，天然绿洲条件Kappa系数提高了0.30。面向对象的影像分析方法能够在一定程度上克服单一光谱特征分类方法的局限性，避免“异物同谱”和“同物异谱”现象带来的混淆，提高天然绿洲和人工绿洲区分的精度。

Object-oriented Natural and Artificial Oasis Distinguishing in Landsat Imagery: Taking Minqin Oasis as an Example

Taking Minqin Oasis in the downstream area of the Shiyang River Basin which is located in the east of Hexi Corridor as an example, the Landsat 8 OLI image was chosen as the data source. Under the consideration of the basic concept of the artificial oasis and natural oasis in this paper, combining with the information of the spectrum, texture, shape and context basing on the image data preprocessing and multi-scale segmentation, we introduce a series of indexes such as NDVI、maximum difference, compactness, shape index, the space adjacency relation and so on to construct a rule set for distinguish between natural oasis and artificial oasis. The obtained results were further compared with the results based on the maximum likelihood method. As a result, the total accuracy of using the object-oriented image analysis method to distinguishing between natural oasis and artificial oasis is 91.75%, and the Kappa coefficient is 0.65 by using the rule set established in this paper. Compared with the results based on the maximum likelihood method, the overall accuracy is improved by 10.40% and the Kappa coefficient is 0.13. The Kappa coefficient of the artificial oasis is increased by 0.19, and the Kappa coefficient of the natural oasis condition is increased by 0.30. The results showed that the object-oriented image analysis method can overcome the limitations of the classification method that only using spectral feature to a certain extent, avoid the confusion caused by the phenomenon of “same object with different spectrums” and “same spectrum with different objects”, and increase the accuracy of distinguishing between the artificial oasis and natural oasis.