Extraction of Jujube Planting Areas in Sentinel-2 Image Based on NDVI Threshold—a case study of Ruoqiang County

This study preliminarily explores the method of setting a single threshold and combining the screened images in the same time period with the threshold to extract the NDVI index from the jujube planting area in the crop area, which is fast, convenient, simple and easy to understand. According to the NDVI time series analysis results of jujube trees and other features in the study area, between June and July of the year, the lowest NDVI value of jujube trees to be extracted is always higher than the highest NDVI value of other features, while the "critical threshold" of jujube trees and other features is NDVI = 0.4. Therefore, the jujube planting area in the study area of simultaneous sentinel-2 image extraction was selected in cooperation with the measured sampling points of the research team in 2021. The jujube planting area in the study area obtained based on the NDVI threshold of this study is 78600 mu. Compared with the result of supervised classification extraction area of 85900 Mu, the extraction effect is in good agreement, indicating that it has certain applicability, and the processing process is fast and convenient.