Abstract
Urban black-odor water is a serious water environmental problem worldwide that seriously affects the living environment and the health of residents. The detection of black-odor water is a primary problem of centralized governance. Remote sensing is an effective means for water-quality monitoring. However, in most urban areas, with their complex underlying conditions, black-odor water always shows an uncertain distribution and small area. Furthermore, because of similar spectral characteristics, it is easily confused with dark objects such as asphalt roads, dark roofs, bridges, river levees, and building shadows. In this article, we propose a new black-odor water detection method, without shadow misjudgment, for complex urban conditions. A remote sensing image from the Chinese high-resolution satellite Gaofen-2 (GF-2) was used for detection. Using in situ water-quality measurement data for verification, the results showed that the proposed method achieved an accuracy of 85.7% while reducing the false alarm rate to 3.5%. Compared to four other existing methods, the proposed method proved to be more practical because it can reduce the false extraction of nonblack-odor water to the greatest extent possible while ensuring accuracy The method proposed in this article has a good effect on the extraction of black-odor water in Nanjing City. Therefore, our method can be applied widely to screening and management of large-scale urban black-odor water and can provide reliable data for centralized treatment.
Highlights
BLACK-ODOR water (BOW) refers to water with an unpleasant color and/or odor [1]
The first was to realize the extraction of water from a complex environment, the second was to remove shadow effects, and the third was to develop a BOW detection method that eliminates shadow misjudgment through the analysis of hyperspectral reflectance data
The results showed that our method can effectively suppress the influence of background information, shadows, on water detection in a complex environment
Summary
Urban BOW is a product of the process of industrialization and is caused mainly by the discharge of pollutants [2] and non-circulation of the water itself. According to the 2015 China Environmental Bulletin, BOW accounts for 8.8% of the more than 900 sections under state control and monitoring in key waters across the country. The “Action Plan for Water Pollution Prevention and Control” issued by the State Council in 2015 required urban built-up areas to complete water quality screening by the end of 2015, begin eliminating BOW by the end of 2017 and generally eliminate BOW by the end of 2030. The detection of urban BOW is extremely urgent. Some of are temporary but others are perennial These features make it difficult to achieve accurate and large-scale detection in a short time. A more accurate and practical way to monitor the distribution of BOW needs to be identified
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