Calibration and validation of the Australian fractional cover product for MODIS collection 6

Abstract

ABSTRACTFractional cover of photosynthetic vegetation (FPV), non-photosynthetic vegetation (FNPV) and bare soil (FBS) is an important input for assessment of the productivity of global pastures and rangelands. Here we describe the updating of this product using the new Moderate Resolution Imaging Spectroradiometer (MODIS) Nadir BRDF-Adjusted Reflectance (NBAR) Collection 6 reflectance product (C6) and a major expansion of the field calibration database. Fractional cover based on the C6 input exhibited reduced bias and root mean square error compared with the Collection 5 (C5) product. The expanded calibration database with more sites in arid areas provided greater separation between reflectance values of end-members for FNPV and FBS. Specific site variations in FNPV and FBS in arid areas could be traced to small but consistent changes in blue and green band, and occasional changes in short wave infrared reflectance in C6 when compared to C5. The recalibration described here provides an Australian fractional cover product with reduced uncertainty and improves the basis for a prototype global product for use in modelling of rangeland and pasture productivity.