Crop Phenology-Based, Object-Oriented Classification Approach Using SENTINEL-2A and NDVI Time Series: Sunflower Crops in Kırklareli TURKEY

Abstract

The aim of this study is to develop a methodology for determining sunflower cultivated areas with the help of high resolution SENTINEL-2A satellite images time series representing the phenological stages of the crop growth cycle, and its application in Kırklareli province. Spectral information representing phenological periods was obtained with the help of satellite images and normalized difference vegetation index (NDVI) time series, and an object-oriented classification approach was developed based on this spectral information database. Segmentation and classification decision tree algorithms were produced by using this spectral information database, object shape criteria and other auxiliary thematic maps. The best performance in segmentation was achieved by increasing the weight coefficient of the "Canny edge” layer, which is the edge determination layer defined in the multiresolution method of "Canny edge” algorithm to define the agricultural parcels. Object-oriented classification was carried out based on the this segmented parcels. First, summer, winter, fallow and continuous green areas were determined through the classification decision tree algorithms. The summer and winter crops were classified using the parcel spectral information of the crop-based learning samples that allocated in field work. The crops for which class definition could not be made were passed through a second elimination in the "unclassified" group and later assigned to their classes. In the last stage, parcels whose class definition could not be made were named as "other" class. According to the confusion matrix and accuracy analysis results, sunflower, which was determined in two classes as early and late sowing, was classified at 98% and 92% accuracy, respectively.