APPLICATION OF SENTINEL-1 MULTI-TEMPORAL DATA FOR CROP MONITORING AND MAPPING R. Nasirzadehdizaji 1, *, F. B. Sanli 1 , Z. Cakir 2 1 Dept. of Geomatic Engineering, Faculty of Civil Engineering, Yildiz Technical University, 34220 Esenler, Istanbul, Turkey - rouhollah.nasirzadehdizaji@std.yildiz.edu.tr, fbalik@yildiz.edu.tr 2 Dept. of Geology, Faculty of Mines, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey - ziyadin.cakir@itu.edu.tr KEY WORDS: Sentinel-1, SAR, Backscatter, Time-series Analysis, Agricultural Monitoring, Crop Mapping ABSTRACT: The Synthetic Aperture Radar (SAR) technique superiority has provided various opportunities in agricultural studies mainly on crop monitoring and management. This has resulted in many different investigations and improvements in crop growth monitoring, crop disaster prediction and providing accurate information to precise farming. In this study, a time-series of Sentinel-1 SAR images were acquired throughout the agricultural season synchronously with the field measurements to investigate the temporal backscatter changes for different crop types. From the backscattering analysis, it was observed that each similar crop type in different test fields due to the distinct methods of irrigation and fertilization has shown different intensity values. However, they all follow a roughly identical backscattering trend during growing stages of the crop and useful information can be extracted, such as estimating irrigation and harvesting time according to the changes made in backscatters. In comparing with ascending orbit in VH and VV polarizations it has indicated that the homogeneity between SAR backscatters is high for each field with the same crop type in descending pass direction with VH polarization. In contrary, high-intensity values are recorded in VV polarization for entire crop types. It is also observed that polarimetric composite images for a different date are useful to roughly identify crop types, and validated with the application of classification methods in the study area. As preliminary results, it is demonstrated that SAR data provide useful information about crops status. Hence, Sentinel-1 SAR data are ideal preference due to its free availability and constant long-term data archive. * Corresponding author 1. INTRODUCTION Agriculture is in amongst important activities that have played a key role in providing food security to a growing population of the world (Soria-Ruiz, 2009). In this regard, sustainable food security is dependent on precise agricultural activities monitoring and the collection of accurate farming information (Canisus, 2017). Precision agriculture is a management strategy that integrates information and communication technologies with the agricultural industry. Therefore, the information of each component of the small area in a farm is used to adapt the type and amount of inputs in those areas in order to evaluate and manage the temporal and spatial variability more precisely. Satellite data are widely used to study and investigate agriculture activities changes as dynamic phenomenon over the time and in terms of quantitative and qualitative agricultural products, estimation of the planted area, the identification of certain types of crops, the growth stages and disaster prediction (Zhang, 1999). Synthetic Aperture Radar (SAR) remote sensing system uses the microwave wavelength portion of the electromagnetic spectrum. Hence, the application of SAR data is very useful in agricultural monitoring due to the sensitivity of the microwave wavelength to the several characteristics of the crops. SAR is an active system independent of illumination sources to obtain data day- and-night and provide reliable and frequent imaging, independently of cloud coverage, as a key factor in the context of agricultural applications (Moreira, 2013). Microwaves can penetrate through clouds where the cloudy sky is a serious obstacle to the application of optical images particularly in a rainy climate. The SAR system has sensitivity to the physical morphology and the geometrical characteristics of the land surface and cover (soil roughness, moisture, vegetation structure, etc.). Therefore, radar sensors collect the echoes of the backscattered signal in a sequential way thus very different to that of optical satellite data, which measure reflected solar light in visible and infrared wavelengths (Wooding, 1995). The two-polar-orbiting satellite constellation (Sentinel-1A and - 1B) equipped with a dual-polarized SAR C-band at a 20 m spatial resolution offers a 6 days repeat frequency in a different operational mode which enables users to access freely available of a constant long-term data archive for applications requiring long-range time-series (Panetti, 2012). This study investigates the potential of Sentinel-1 polarimetric SAR backscatter data in an agricultural area for growth monitoring of different crop types (maize, sunflower, wheat and potato) and crop mapping using that polarimetric composite of images which are produced from multi-temporal analysis. 1. MATERIALS AND METHODOLOGY 1.1 Study site description and field surveys The Konya basin in the central Anatolia Turkey, (38⁰ 40′ N, 32⁰ 26′ E) which is about 40 km 2 , was selected for field measurements and satellite images collection (Figure 1). The study area has partially flat topography with a gentle slope (2%– The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLII-4/W18, 2019 GeoSpatial Conference 2019 – Joint Conferences of SMPR and GI Research, 12–14 October 2019, Karaj, Iran This contribution has been peer-reviewed. https://doi.org/10.5194/isprs-archives-XLII-4-W18-803-2019 | © Authors 2019. CC BY 4.0 License. 803