A study on rice field edge extraction in Radarsat SAR images

In order to make an accurate estimation of how much rice has been planted, it is essential to calculate the area of rice fields as precise as possible. Therefore, to delineate the edge of rice fields and remove the area occupied by the widened ditch roads around the rice fields caused by corner reflector effect in SAR images, have become a critical topic in rice monitoring and yield estimation using SAR images. To detect the linear features of rice fields for rice monitoring, this paper introduces an edge detection and extraction scheme in Radarsat SAR images by applying a two-dimensional (2D) filter in eight directions. To reduce the isolated speckle noise on SAR images, an sigma-filter is performed firstly and then the two-dimensional filter in eight directions can be selected and applied to detect edges. Finally, a nonlinear operator is used to threshold its magnitude and produces the edge maps of Radarsat SAR images. The proposed scheme achieves positive results of extracting linear features, reducing the speckle noise effectively, and meeting the need of practical radar remote sensing application in rice monitoring and yield estimation