Parametric and nonparametric regression methods have been proven to successfully retrieve crop canopy parameters. However, once those models are calibrated for certain crops or geographical place their applicability to other crops and places is still unclear and it is an important consideration in an operational context. The tested models are parametric with two or three bands Vegetation Indices and different fitting functions and nonparametric linear and non-linear kernel based. The studied crop canopy parameters are aboveground fresh and dry biomass, vegetation fraction, mean plant height and nitrogen concentration in biomass. For calibration of the models, in-situ data from winter rapeseed and wheat crops with bare soil pixel added and remote sensing data from Sentinel-2 is used. In this study two different scenarios are considered in order to determine the applicability of both types of models for rapeseed and wheat crop parameters retrieval: 1) When applying models to the crop and period they are calibrated for: only the models for wheat before and after winter period give very good results for all studies parameters. Gaussian Processes Regression and its Variational Heteroscedastic variant with dimensionality reduction are the best performing for most of the parameters’ retrieval. Three bands Vegetation Index are the best parametric methods; 2) When applying the models to the crop and period they are not calibrated for: no model gives satisfactory results for any of the studied parameters.
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