锡林郭勒草原遥感植被物候的地面照相验证

Ground photography verification of remote sensing-derived vegetation phenology in the Xilinguole grassland

利用内蒙古锡林郭勒整个生长季节的草地物候照相观测数据和不同的卫星遥感数据,分析了二者之间的统计关系。结果表明,1)MODIS可见光波段的反射率与地面照相观测的平均亮度值之间呈显著正相关(P<0.05),其中,500m空间分辨率的MODIS反射率与地面照相平均亮度值之间的相关性最高,而TM/ETM+反射率与地面照相平均亮度值之间的相关不显著(P>0.05);2)MODIS归一化植被指数(NDVI)与地面照相相对绿度指数(G%)之间的正相关明显高于其他植被指数与绿度指数之间的相关性;3)基于遥感与地面照相数据提取的物候发生日期之间的误差大多在7d之内。由此可见,通过地面照相可以客观地评价遥感物候监测的可靠性,这对于选择适宜的遥感数据源和物候监测指标,具有重要的意义。

Using photographic observation data of grassland phenology over the entire growing season and different satellite remote sensing data in Xilinguole of Inner Mongolia,we analyzed statistical relationships between the two datasets.The results showed that MODIS reflectance in visible light band positively correlated(P<0.05)with the ground photographic digital number,in which the most significant correlation appeared between MODIS reflectance in 500 mspatial resolution and the ground photographic digital number.Nevertheless,TM/ETM+reflectance did not significantly correlate(P>0.05)with the ground photographic digital number.The positive correlation between MODIS Normalized Difference Vegetation Index(NDVI)and relative greenness index from ground photography(G%)was obviously higher than those between other vegetation indices and greenness indices.Errors between phenological occurrence dates derived from remote sensing and ground photography data were mostly within 7days.In conclusion,the reliability of remote sensing phenology monitoring by means of ground photography was of crucial for selecting appropriate remote sensing data source and phenological monitoring index.