Department of Civil Engineering and Geomatics, Faculty of Engineering and Technology, Cyprus University of Technology, P.O. Box 50329, 3036, Lemesos, Cyprus.
Environ Monit Assess. 2009 Dec;159(1-4):281-92. doi: 10.1007/s10661-008-0629-3. Epub 2008 Dec 6.
Although there have been many studies conducted on the use of satellite remote sensing for water quality monitoring and assessment in inland water bodies, relatively few studies have considered the problem of atmospheric intervention of the satellite signal. The problem is especially significant when using time series multi-spectral satellite data to monitor water quality surveillance in inland waters such as reservoirs, lakes, and dams because atmospheric effects constitute the majority of the at-satellite reflectance over water. For the assessment of temporal variations of water quality, the use of multi-date satellite images is required so atmospheric corrected image data must be determined. The aim of this study is to provide a simple way of monitoring and assessing temporal variations of water quality in a set of inland water bodies using an earth observation- based approach. The proposed methodology is based on the development of an image-based algorithm which consists of a selection of sampling area on the image (outlet), application of masking and convolution image processing filter, and application of the darkest pixel atmospheric correction. The proposed method has been applied in two different geographical areas, in UK and Cyprus. Mainly, the method has been applied to a series of eight archived Landsat-5 TM images acquired from March 1985 up to November 1985 of the Lower Thames Valley area in the West London (UK) consisting of large water treatment reservoirs. Finally, the method is further tested to the Kourris Dam in Cyprus. It has been found that atmospheric correction is essential in water quality assessment studies using satellite remotely sensed imagery since it improves significantly the water reflectance enabling effective water quality assessment to be made.
尽管已经有许多研究致力于利用卫星遥感技术监测内陆水体的水质，但很少有研究考虑卫星信号的大气干扰问题。当使用时间序列多光谱卫星数据监测水库、湖泊和水坝等内陆水域的水质监测时，这个问题尤其严重，因为大气效应对水上卫星反射率的影响占大多数。为了评估水质的时间变化，需要使用多日期的卫星图像，因此必须确定大气校正后的图像数据。本研究旨在提供一种基于地球观测的简单方法，用于监测和评估一组内陆水体的水质时间变化。所提出的方法基于开发一种基于图像的算法，该算法包括在图像上选择采样区域（出水口）、应用掩蔽和卷积图像处理滤波器，以及应用最暗像素大气校正。该方法已在英国和塞浦路斯两个不同的地理区域应用。主要是将该方法应用于 1985 年 3 月至 11 月期间在英国伦敦西部的泰晤士河谷地区获取的一系列 8 张存档的 Landsat-5 TM 图像，该地区有大型水处理水库。最后，该方法在塞浦路斯的库里斯大坝进一步进行了测试。研究发现，大气校正对于使用卫星遥感图像进行水质评估研究至关重要，因为它可以显著提高水体反射率，从而能够进行有效的水质评估。
