ISPRS-Annals ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences ISPRS-Annals ISPRS Ann. Photogramm. Remote Sens. Spatial Inf. Sci. 2194-9050 Copernicus Publications Göttingen, Germany 10.5194/isprs-annals-IV-1-W1-83-2017 LANDSAT BIG DATA ANALYSIS FOR DETECTING LONG-TERM WATER QUALITY CHANGES: A CASE STUDY IN THE HAN RIVER, SOUTH KOREA Seong J. C. 1 Hwang C. S. 2 Gibbs R. 1 Roh K. 1 Mehdi M. R. 3 Oh C. 4 Jeong J. J. 5 Dept. of Geosciences, University of West Georgia, Carrollton, Georgia, USA Dept. of Geography, Kyunghee University, Seoul, South Korea NED University of Engineering & Technology, Karachi, Pakistan Dept. of GIS Engineering, NamSeoul University, CheonAn, South Korea Dept. of Geography, SungShin Women's University, Seoul, South Korea 30 05 2017 IV-1/W1 83 89 Copyright: © 2017 J. C. Seong et al. 2017 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://isprs-annals.copernicus.org/articles/IV-1-W1/83/2017/isprs-annals-IV-1-W1-83-2017.html The full text article is available as a PDF file from https://isprs-annals.copernicus.org/articles/IV-1-W1/83/2017/isprs-annals-IV-1-W1-83-2017.pdf

Landsat imagery satisfies the characteristics of big data because of its massive data archive since 1972, continuous temporal updates, and various spatial resolutions from different sensors. As a case study of Landsat big data analysis, a total of 776 Landsat scenes were analyzed that cover a part of the Han River in South Korea. A total of eleven sample datasets was taken at the upstream, mid-stream and downstream along the Han River. This research aimed at analyzing locational variance of reflectance, analyzing seasonal difference, finding long-term changes, and modeling algal amount change. There were distinctive reflectance differences among the downstream, mid-stream and upstream areas. Red, green, blue and near-infrared reflectance values decreased significantly toward the upstream. Results also showed that reflectance values are significantly associated with the seasonal factor. In the case of long-term trends, reflectance values have slightly increased in the downstream, while decreased slightly in the mid-stream and upstream. The modeling of chlorophyll-a and Secchi disk depth imply that water clarity has decreased over time while chlorophyll-a amounts have decreased. The decreasing water clarity seems to be attributed to other reasons than chlorophyll-a.