In June 2015, the Liaoning Provincial Environmental Engineering Assessment and Audit Center used the UAV infrared and visible light synchronous remote sensing technology to conduct monitoring experiments on the Honghe Mountain section of the Weihe River to test the practical application effect of the drone in the environmental monitoring work.
The infrared image mainly reflects the thermal radiation information of the target. Objects of different temperatures have obvious characteristics in the infrared band, and the lower the temperature, the deeper the color. The water discharged from some drainage outlets has a temperature difference between the river and the river. Generally speaking, the drainage temperature of steel, thermal power and other enterprises is higher than that of river water; during the day, the temperature of the water discharged by the culvert is lower than that of the river under the sunlight. In the infrared image, the water discharged from the drain is that the diffusion state of the river water is very obvious. The sewage discharged from the sewage outlet diffuses downstream in the direction of the water flow and spreads on the plane, which is strip-shaped and quickly oozes with the river water. A dilution occurs. Using these features, it is possible to effectively check the dark drains that are being drained in the grass on both sides of the river.
The infrared remote sensing monitoring of the drone is broad, and the water body diffusion process is easy to see the whole picture. The information such as the source of the sewage, the direction of the diffusion, the scope of the impact, and the mixed dilution with the river water can be observed. In order to find out the ins and outs of sewage, the use of infrared remote sensing images along the river can effectively detect the source of water pollution.
1. Monitoring point selection
The monitoring points and monitoring contents are as follows:
Table 1 Monitoring points and contents
Monitoring point | Monitoring content | Monitoring purpose |
Luohe (Hongtoushan) section | The application of visible light and infrared light technology finds suspicious sewage outlets along the river. | Conduct an investigation of the abnormal sewage inlet into the river and monitor whether there is abnormal discharge behavior. |
2. Infrared and visible image combined analysis
The visible and infrared light video is taken on the red-transparent mountain section, and the screenshots are compared according to the possible presence of the sewage outlet in the video, and the field analysis is performed. The results are shown in Figures 1-4.
The sewage outlet in Figure 1 is for the residential area to discharge domestic sewage into the river through the pipeline. The scene has odor, the water flow is small, and the visible light resolution is not obvious. The infrared light picture clearly shows that the discharged sewage is inconsistent with the surrounding water body.
In Figure 2, the sewage outlet is sewage from the waterworks, the discharge of wastewater is relatively clear, the water flow is small, and the visible light picture is not clearly distinguishable. The infrared light picture clearly shows that the discharged sewage is inconsistent with the surrounding water body.
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