Crop Phenology Retrieval Using Polarimetric Signatures

Today, agricultural products have important role in human life. Phenology monitoring of agricultural fields by remote sensing and synthetic aperture radar is useful because it provides key information for farmers with extensive fields. This paper deals with the retrieval of phenological stages of agricultural crops by the degree of polarization (DoP), co-polarized and cross-polarized polarimetric signatures. The DoP is taken as one of the main parameters of the scattered wave, which is received polarization-basis rotation invariant. It is shown that the DoP signature provides information about the phenology that can be complementary to that provided by the conventional polarization signatures. The phenology retrieval is performed by a new approach based on the polarimetric signatures and matching parameters. In this approach, first a signature of each phenological stage is randomly selected as the reference signature. Then, using the matching parameters, the similarity values between the reference and other signatures are calculated. Finally, the phenological stages are identified by analyzing the results. The time series of RADARSAT-2 fine quad-pol images acquired over the Barrax area have been used in this study. This dataset includes a dense revisit time along the growth cycle by combining different incidence angles and different orbit passes (ascending/descending). The experimental results show the good performance of using the DoP signatures, average accuracy 63%, and the similarity between them for retrieving the phenological stages. The DoP signatures are less sensitive to the incidence angle, but more dependent on the physical characteristics of the crops. The results also demonstrate that the matching parameters based on the geometric features of signatures can provide valuable information especially for the oat crop.