This study investigates the potential for remote sensing of lake water bathymetry and geochemical by 1) examining the empirical based technique for retrieving depth information from passive optical image worldview-2 s...This study investigates the potential for remote sensing of lake water bathymetry and geochemical by 1) examining the empirical based technique for retrieving depth information from passive optical image worldview-2 satellite data, 2) performing atmospheric correction, 3) assessing the accuracy of spectrally based depth retrieval under field condition via field measurement, 4) producing bathometry and geochemistry mapping by examining spectral variations for identifying pairs of wavelengths that produce strong linear correlation coefficient between the band ratio. The results indicate that optical remote sensing of bathymetry and geochemical investigation is not only feasible but more accurate under conditions of typical lake water, supporting field survey. The Pearson correlation matrix (R) between the examined water samples/depth and the TOA reflectance values of the worldview-2 (WV-2) satellite data have been investigated and found good correlation. The models developed using the combination of different band pairs also show high accuracy. Cartographical maps were generated depending on the linear correlation coefficient between the measured parameters and the TOA reflectance values of the worldview-2 data. The investigation shows that dissolved oxygen (DO) of the lake water is slight lower than the permissible limit of Saudi standards for lake water. The shallow water has high DO concentration, whereas the deeper shows significantly lower down. Electrical conductivity measurements serve as a useful indicator of the degree of mineralization in the water sample. All the samples which have EC exceed limit. The spatial distribution of EC and TDS inferred that the EC and TDS concentration is the highest at the eastern part of the lake whereas concentration drops down towards the southern side. This study confirms that remote sensing incorporated with GIS and GPS could afford an integrated scheme for mapping water quality and bathometry of the surface water.展开更多
文摘全球气候变暖严重影响冰川的稳定性,南极多条冰川表面发生塌陷。由于缺少高空间和高时间分辨率的南极地表高程模型DEM(Digital Elevation Model),目前单支冰川表面时空变化的研究不充分。利用2011年—2016年11期南极参考高程模型REMA(The Reference Elevation Model of Antarctica)数据,开展东南极达尔克冰川表面塌陷区域的高程变化监测,并利用Landsat 7/8和Worldview-2光学影像等数据分析塌陷过程和原因。结果表明,达尔克冰川在2013年发生了一起严重的塌陷事件,塌陷深度最大约45.29 m,造成了约26.29×10^(6)m^(3)的水体损失;塌陷发生后,该区表面高程不断增加,于2016年恢复至塌陷前的高程。塌陷区具有明显的整体性沉降特征,并存在融水聚集,推测塌陷和达尔克冰川冰下湖的排水过程存在密切的联系。本研究证明达尔克冰川存在较大的不稳定性,同时验证了REMA数据监测冰川表面塌陷的可行性,为未来精细化监测南极冰盖/冰架响应气候变化提供技术参考。
文摘This study investigates the potential for remote sensing of lake water bathymetry and geochemical by 1) examining the empirical based technique for retrieving depth information from passive optical image worldview-2 satellite data, 2) performing atmospheric correction, 3) assessing the accuracy of spectrally based depth retrieval under field condition via field measurement, 4) producing bathometry and geochemistry mapping by examining spectral variations for identifying pairs of wavelengths that produce strong linear correlation coefficient between the band ratio. The results indicate that optical remote sensing of bathymetry and geochemical investigation is not only feasible but more accurate under conditions of typical lake water, supporting field survey. The Pearson correlation matrix (R) between the examined water samples/depth and the TOA reflectance values of the worldview-2 (WV-2) satellite data have been investigated and found good correlation. The models developed using the combination of different band pairs also show high accuracy. Cartographical maps were generated depending on the linear correlation coefficient between the measured parameters and the TOA reflectance values of the worldview-2 data. The investigation shows that dissolved oxygen (DO) of the lake water is slight lower than the permissible limit of Saudi standards for lake water. The shallow water has high DO concentration, whereas the deeper shows significantly lower down. Electrical conductivity measurements serve as a useful indicator of the degree of mineralization in the water sample. All the samples which have EC exceed limit. The spatial distribution of EC and TDS inferred that the EC and TDS concentration is the highest at the eastern part of the lake whereas concentration drops down towards the southern side. This study confirms that remote sensing incorporated with GIS and GPS could afford an integrated scheme for mapping water quality and bathometry of the surface water.
