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基于实测数据建立了FPAR、LAI的植被指数估算模型(NDVI、RVI、NDWI),并将其应用于MODIS BRDF数据对德惠地区玉米FPAR、LAI进行估算,然后将MODIS 15A2 FPAR/LAI产品值分别与BRDF估算值、地面实测值进行对比分析。主要得出以下结论:植被指数NDVI、RVI都能较好地用于实测数据和MODIS BRDF数据的FPAR、LAI估算;NDWI虽然在实测数据中估算玉米FPAR、LAI的效果优于NDVI、RVI,但其应用于MODIS BRDF数据估算FPAR、LAI时,效果却较差。BRDF数据估算FPAR与MODIS 15A2 FPAR值的关系因生长时期不同而异,在玉米生长前期,前者高于后者,而生长后期两者却较相近;BRDF估算LAI值一直都高于MODIS 15A2LAI产品值。生长季前期,MOD15A2 FPAR、LAI值接近实测值,而在后期却高于实测值。通过分析也表明,玉米苗期MODIS 15A2 FPAR数值变化范围较小,产品算法对实际FPAR变化尚不够敏感,这可能是影响MODIS FPAR产品精度的一个原因。
Based on the measured data, the vegetation index estimation models (NDVI, RVI, NDWI) of FPAR and LAI were established and applied to MODIS BRDF data to estimate FPAR and LAI of maize in Dehui region. Then, the MODIS 15A2 FPAR / Compared with BRDF estimates and ground measurements. The main conclusions are as follows: Vegetation index NDVI and RVI can all be used for FPAR and LAI estimation of measured data and MODIS BRDF data. NDWI Although the estimation of corn FPAR and LAI is better than NDVI and RVI in the measured data, Its application in MODIS BRDF data estimation FPAR, LAI, the effect is poor. The relationship between FPAR and MODIS 15A2 FPAR values in BRDF data was different according to the growth period. In the early stage of maize growth, the former was higher than the latter, while the latter was more similar. The LAI value of BRDF was always higher than that of MODIS 15A2LAI . In the early growing season, the MOD15A2 FPAR and LAI values were close to the measured values, but higher than the measured values in the later period. The analysis also showed that the range of MODIS 15A2 FPAR values in maize seedlings was small and the product algorithm was not sensitive enough to the actual FPAR changes, which may be one of the reasons that affect the accuracy of MODIS FPAR products.