Agricultural plains monitoring using interferometric SAR data

Abstract

By means of Interferometric Synthetic Aperture Radar (InSAR) data, our aim in this work is to examine the ground deformation changes of eight agricultural plains in northwestern part of Turkey. This part of the country is tectonically active, highly vegetated, experiencing rapid human population growth and infrastructural change. All these influences make the agricultural plains monitoring and control challenging. One of the problems is that a stable solution cannot be achieved through traditional, time and resource consuming land-dwelling methods. Improved, yet insufficient are the optical remote sensing systems, which are greatly reliant on appropriate weather conditions. As a method, on the other hand, InSAR holds a viable solution that offers high spatial, and lately with Sentilel-1 satellite constellation of the European Space Agency (ESA) data also provides high temporal resolution. When data are acquired from two different perspectives, contrary to optical images InSAR gives an opportunity of 3-dimensional measurements of earth' surface displacements. For interferograms generation of Sentinel-1 TOPS IW mode data, we applied to an open-source processing tool, known as GMTSAR (Generic Mapping Tools SAR). We mapped the ground surface deformation field of the agricultural basins using SAR data spanning between the years of 2014 and 2017. In order to calculate the deformation velocity field of the agricultural basins we used the Stanford Method for Persistent Scatterers technique on three separate Sentinel-1 tracks (ascending T58 & T131 and descending T138). Seasonal fluctuations are noticeably observed in the results. Nevertheless, the results retain a clear declining trend in the areas of six out of eight cultivated plains (75%). The estimated surface deformation rates obtained from both ascending and descending tracks vary among the plains reaching the maxima of 2 (+/−1) cm/yr for Bursa and Karacabey agricultural plains. Bandirma and Manayas were the two other two plains where we did not find any vertical or horizontal displacements.