Rizzi, R, Rudorff, BFT, Shimabukuro, YE, Doraiswamy, PC (2006). Assessment of MODIS LAI retrievals over soybean crop in Southern Brazil. INTERNATIONAL JOURNAL OF REMOTE SENSING, 27(19), 4091-4100.
In the present paper we have looked into the excessive occurrence of 255 standard fill value retrievals in Collection 4 MODIS LAI product over soybean areas from crop year 2001/2002 to 2004/2005, in Southern Brazil. The 255 standard fill value indicates that no leaf area index (LAI) retrieval was possible for the considered pixel. Time series of eight-day composite LAI images (MOD15A2) and 16-day composite NDVI images (MOD13Q1) were both compared with a soybean reference map derived from multitemporal Landsat images. The Land Cover Type 3 product (MOD12Q1) was also analysed to verify if the occurrence of those retrievals was related to misclassification of the broadleaf crops biome. Results indicated that the 255 standard fill value retrievals in Collection 4 LAI product were mainly related to soybean areas during peak growing season and occurred in every crop year we have studied. Eventual misclassification in the biome map was not the cause of those retrievals in the Collection 4 MODIS LAI product.