Regional crop monitoring and discrimination based on simulated ENVISAT ASAR wide swath mode images

Abstract

The current paper investigates the potential contribution of ENVISAT wide swath (WS) images for discrimination and monitoring of crops at a regional scale. The study was based on synthetic aperture radar (SAR) images acquired throughout an entire growing season. Advanced synthetic aperture radar sensor (ASAR) images in both narrow swath (NS) and WS modes were simulated based on 15 European Remote Sensing (ERS) satellite images recorded over Belgium. Unlike ‘real’ ASAR imagery, this exercise provided a consistent data set (i.e. same incidence angle, same acquisition date, same acquisition hour) to study the impact of spatial resolution on the SAR signal information content. A quantitative approach using 787 parcels of medium field size and various data combinations assessed monitoring and discrimination capabilities for six crop types: wheat, barley, grasses, sugar beet, maize and potato. The spatial resolution impact of the ASAR sensor was discussed with respect to the field size by comparing the results obtained from NS (30 m) and WS (150 m) mode images. WS temporal profiles were able to discriminate the various crops of interest and were representative of the crop development observed in the region. Furthermore, parcel‐based unsupervised classifications successfully discriminated between grass, wheat, barley and other crops of large parcels (success rate of 83%). Dedicated interpretation schemes were developed in order to discriminate between cereal crops.

Keywords:

• Crop monitoring
• Crop discrimination
• ENVISAT
• Wide swath‐ASAR
• Coarse spatial resolution
• Synthetic aperture radar

Acknowledgments

This research was carried out in the framework of the project ‘Dedicated Remote Sensing Product Generation for the Agro‐Industry: Cereal Case’ lead by Synoptics b.v. (NL) (van der Werf 2000) and sponsored by the Data User Programme (ESA‐ESRIN). The authors are also grateful to the Belgian Ministry of Agriculture – CTS for the field boundary data and the AGRIFISH unit of the Joint Research Centre for the European field size distribution statistics. The SAR data were provided by ESA in the framework of the ERS‐1/2 Pilot Project A02‐B102.