基于RGB图像的刺槐季节变化监测适用指数研究

The Evaluation of Efficiency of Color Metrics in Monitoring Robiuia Pseudoacacia Phenology based on RGB Images

随着普通数字相机的广泛使用,利用普通数字相机拍摄获得的RGB图像提取植被生长的特征时间点是监测植被季节变化的一种有效方式。为此提出了多个为量化特征时间点的提供数据基础的颜色指标,但其有效性仍是这一植被监测方法的制约因素。以黄土高原广布的刺槐为对象,利用缩时相机获取的数字照片为基本数据。通过提取绝对绿度指数(Green Excess Index,ExG)、相对绿度指数(Green Chromatic Coordinate,Gcc)、绿红植被指数(Green Red Vegetation Index,GRVI)和色相指数(Hue based on HSL,Hue)等颜色指数,比较了上述4个颜色指数在平均值法和最大亮度法两种分析方法下提取植被生长过程时间节点的效果,与实际观测结果相比较,遴选最佳指数。结果表明:基于平均值法的ExG指数的提取的生长期开始(Start of the Seasonality,SOS)、生长期结束(End of the Seasonality,EOS)最接近实测值,ExG可以较好地拟合出刺槐生长过程中的关键时间节点。该方法实现了对植被生长状况主要时间节点的自动提取,弥补了遥感监测和人工物候观测的不足,为生态系统植被生长变化研究补充了新的数据来源。

The widely application of digital camera，especially the appearance of time-lapse camera，inspired the monitoring vegetation seasonal dynamic using time-series RGB imagery.Extract critical temporal stage of vegetation dynamic is the most useful aspect.Color index including Green Excess Index（ExG），Green Chromatic Coordinate（Gcc），Green Red Vegetation Index（GRVI），and Hue based on HSL（Hue） are the most widely used metrics.However，their efficiency for specific plants may differ.In this study，the efficiency of four color indices mentioned above were tested taking RGB imagery of Robiuia Pseudoacacia as data source.The critical timing point of plant growth and senescence reflected by greenness of leaves were used to pick out the most efficiency color index.The results showed that the best SOS（Start of the Seasonality），EOS（End of the Seasonality） can be extracted using ExG following the