两种应用场景下NDVI时间序列数据拟合方法研究

Study on NDVI Time Series Data Fitting Method Based on Two Application Scenarios

植被覆盖指数(NDVI)时间序列数据集包含地表植被的长势、生长周期、时空变化等信息,其拟合重建结果可应用于物候信息提取、生态质量评价、人类活动扰动识别、覆被变化动态监测等方面。基于TIMESAT软件,选取物候参数提取和扰动识别2个应用场景,结合地面站点数据和Jacknife法模拟数据,对比分析非对称高斯函数拟合法(AG法)、双Logistic函数拟合法(D-L法)和Savitzky-Golay滤波法(S-G法)3种方法的拟合效果。结果表明:(1)3种方法拟合重建后提取的生长开始时间(SOS)、生长结束时间(EOS)、生长周期(LOS)等物候参数接近站点数据,AG法和D-L法保持NDVI时序曲线整体变化特征的能力较强,提取的SOS和EOS更接近站点数据;(2)人类活动扰动识别应用场景中,S-G法在滤波时能够最大限度地保留时序曲线细节变化,恢复速率相关系数达到0.618,回归估计标准差低于AG法和D-L法,因此识别精度最优。

The NDVI time series data contains information about the growth,growth period,spacial-temproral changes of surface vegetation,and the fitting reconstruction results are applied to phenological information extraction,ecological quality evaluation,human activity disturbance recognition,dynamic monitoring of mulching change,etc.Based on TIMESAT software,we select two application scenarios,combining ground station data and Jacknife method,simulation data,and analyze the fitting effect of asymmetric Gaussian function(AG),double Logistic function(D-L)and Savitzky-Gray method(S-G).The results showed that the extracted growth start time(SOS),growth end time(EOS)and growth cycle(LOS)and other terminal parameters are close to site data,AG and D-L maintain the overall change characteristics of NDVI timing curve,and the extracted growth start time and growth end time are closer to site data.In human activity disturbance recognition application scenarios,S-G method can maximize the timing curve detail changes during filtering,so the recognition accuracy is better than AG and D-L methods,with recovery rate reaching at 0.618 and estimated standard deviation of regression lower than AG and D-L method.