Nghiên cứu các chỉ số nhận biết nước từ ảnh Sentinel-2 trên nền Google Earth Engine: áp dụng cho thành phố Sa Đéc, tỉnh Đồng Tháp

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Thông tin xuất bản: Tạp chí Khoa học và Công nghệ Thủy lợi, 2020

Mô tả vật lý: tr.113

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ID: 300202

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Bài báo này trình bày các kết quả nghiên cứu ba chỉ số NDWI, MNDWI và WNDWI cho nhận biết, phân biệt và giải đoán pixel có nước và không nước từ ảnh Sentinel-2 trong thành phố Sa Đéc, tỉnh Đồng Tháp trên nền Google Earth Engine. Bộ lọc thông cao trước tiên được áp dụng để đồng nhất độ phân giải theo không gian cho dải băng hồng ngoại sóng ngắn (SWIR) từ 20 về 10 m trong vùng nghiên cứu. Các diện tích nước và không phải nước trong miền quan tâm sau đó được số hóa trực tiếp từ Google Earth sử dụng công cụ GIS để tạo bộ dữ liệu tham chiếu. Tiếp theo, phân tích độ nhạy của giá trị ngưỡng và hệ số trọng số được thực hiện khi sử dụng chỉ số WNDWI, kết quả thể hiện rằng giá trị -0.11 và 0.50 được xác định tương ứng cho giá trị ngưỡng và hệ số trọng số. Sai số tổng thể, hệ số kappa, sai số EC và EO lần lượt tương ứng là 0,98, 0,85, 0,015 và 0,006. Trong số ba chỉ số đã chọn, chỉ số WNDWI và MNDWI phù hợp nhất để phát hiện các vùng nước trong khu vực nghiên cứu, với sai số tổng thể >
0,98 và hệ số kappa >
0,84. Cuối cùng, khả năng và hiệu quả của việc ứng dụng GEE cho việc giải đoán ảnh cũng được thảo luận.This paper presents the results of using three popular water indices namely NDWI, MNDWI, and WNDWI on detecting water bodies for the Sa Dec city, Dong Thap province based on Google Earth Engine (GEE) cloud platform. The high pass filter is firstly applied for pan-sharpening of the shortwave infrared (SWIR) band from 20 to 10 m in spatial resolution of the domain of interest. The real water and non-water areas in the domain of interest are then digitized directly from Google Earth using the GIS tool in order to create the reference dataset. Next, sensitivity analysis of the threshold value and weighted coefficient are performed when using the WNDWI, resulting in values of -0.11 and 0.50 are obtained for the threshold value and weighted coefficient, respectively. The overall accuracy, kappa coefficient, error of commission and error of omission equal 0.98, 0.85, 0.015 and 0.006, respectively. Among three selected water indices, WNDWI and MNDWI are the most suitable indices for detecting water bodies in the studied area, with the overall accuracy>
0.98 and kappa coefficient>
0.84. Finally, capacity and time consuming on detecting water bodies using Sentinel-2 images based on GEE are also discussed.

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