AVHRR、SPOT-VGT和MODIS 3种NDVI遥感数据在韩江流域的对比分析

A comparative analysis of AVHRR,SPOT-VGT and MODIS NDVI remote sensing data over Hanjiang River basin

【目的】寻找最能真实反映南方地区植被变化状况的遥感数据,并将其用于评价土地覆被变化及其带来的影响.【方法】通过分析韩江流域2001—2006年间AVHRR、SPOT-VGT和MODIS 3种归一化植被指数(NDVI)遥感数据,比较它们对不同植被响应特征的异同,并采用线性回归方法分析它们的相关关系.【结果和结论】3种NDVI遥感空间分布总体格局大体一致,且MODIS和SPOT-VGT的NDVI空间分布吻合良好.MODIS传感器波段宽度窄、空间分辨率高,对地物分辨能力高,NDVI在流域内的变化范围大,数值分布分散.3种NDVI的季节变化步调基本一致,幅度相当.MODIS NDVI最能精确反映地面植被覆盖的变化,而AVHRR NDVI反映的流域地面植被变化情况与实际不相符.3种NDVI反映的各种植被季节变化情况基本一致,MODIS NDVI与SPOT-VGT NDVI的相似度更高.MODIS NDVI能够明显区分农作物、郁闭灌木林和草地的季节变化与其他植被的不同,比SPOT-VGT NDVI和AVHRR NDVI能更好地反映地面植被的多样性和植被覆盖的变化.在全流域和各种植被类型上,3种NDVI两两间都表现出一定的线性关系,其中MODIS NDVI与SPOT-VGT NDVI间的线性关系最强.由MODIS NDVI与AVHRR NDVI的线性回归关系预测的韩江流域2000年的NDVI与实测值吻合良好,为MODIS NDVI时间序列向历史年份拓展提供了思路.

【Objective】To select an optimum time series in remote sensing data for evaluating land cover changes and their impacts on southern China. 【Method】Three types of remote sensing NDVI data from AVHRR,SPOT-VGT and MODIS were analysed to compare their similarities and differences in different vegetation types over Hanjiang River basin from 2001 to 2006,and their correlations were analysed using linear regression method. 【Result and conclusion】These data had generally similar distribution patterns in space. MODIS and SPOT-VGT NDVI matched well. MODIS could recognize objects more clearly on the earth surface due to its spectrally narrow sensors with high spatial resolution. In MODIS NDVI,values varied within a wide range,therefore more vegetation types could be detected. Three types of NDVI changed seasonally similar to the same amplitude. MODIS NDVI reflected vegetations seasonally change more accurately. In AVHRR NDVI,some vegetation types change did not match with the actual situation. Although different vegetation types seasonally changed in the same way in three types of NDVI,changes in a more temporally identical pace could be found in MODIS NDVI and SPOT-VGT NDVI com-pared with AVHRR NDVI. MODIS NDVI could distinguish seasonal changes of croplands,closed shrublands and savannas from other vegetation types. It showed that MODIS NDVI had a higher resolution on reflecting vegetation types and their development compared to SPOT-VGT NDVI and AVHRR NDVI.Throughout the whole basin and on a variety of vegetation types,there were some linear relationships among three NDVIs,while the linear relationship between MODIS NDVI and SPOT-VGT NDVI was the strongest. Based on the linear regression of MODIS NDVI and AVHRR NDVI,MODIS NDVI was estimated accurately consistent with the measured values of NDVI of Hanjiang River basin in 2000. MODIS NDVI time series can provide developing ideas of the historical years.