# Mapping Aquaculture Ponds for the Coastal Zone of Asia with Sentinel-1 and Sentinel-2 Time Series
## 3 Data and Methods
### Satellite Data Processing  
In this study, we utilized all available Sentinel-1 IW GRDH and Sentinel-2 L2A data from 1 January 2019 to 31 December 2019, provided as an analysis-ready data (ARD) cube within the satellite imagery archive by the Google Earth Engine team [28]. The global datasets of the twin-satellite missions Sentinel-1 and Sentinel-2 have been available since October 2014 (Sentinel-1A) and June 2015 (Sentinel-2A), respectively. Based on experience from a previous study [32] on the use of Sentinel-1 SAR data for the mapping of aquaculture for four river deltas in Asia, the multi-sensor approach presented in this study has been \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Country** & \multicolumn{2}{c}{**Total \({}^{*}\)**} & \multicolumn{2}{c}{**Fishes**} & \multicolumn{2}{c}{**C crustaceansans**} & \multicolumn{2}{c}{**Mollusks**} \\ \hline  & **tons** & **World** & **tons** & **World** & **tons** & **World** & **tons** & **World** \\  & **Share (\%)** & **tons** & **Share (\%)** & **tons** & **Share (\%)** & **tons** & **Share (\%)** \\ \hline China & 48,246,255 & 56.54 & 27,086,062 & 48.09 & 5,674,350 & 54.14 & 14,579,369 & 83.07 \\ India & 7,795,000 & 9.13 & 7,005,792 & 12.44 & 776,208 & 7.41 & 13,000 & 0.07 \\ Indonesia & 5,950,000 & 6.97 & 4,913,000 & 8.72 & 977,800 & 9.33 & 58,400 & 0.33 \\ Vietnam & 4,442,257 & 5.21 & 3,137,200 & 5.57 & 977,157 & 9.32 & 315,000 & 1.79 \\ Bangladesh & 2,488,600 & 2.92 & 2,342,768 & 4.16 & 145,832 & 1.39 & / & / \\ Myanmar & 1,082,141 & 1.27 & 1,019,886 & 1.81 & 62,255 & 0.59 & / & / \\ Thailand & 964,266 & 1.13 & 431,423 & 0.77 & 384,567 & 3.67 & 116,135 & 0.66 \\ Philippines & 858,277 & 1.01 & 709,317 & 1.26 & 87,345 & 0.83 & 61,615 & 0.35 \\ Japan & 598,229 & 0.70 & 278,429 & 0.49 & 1400 & 0.01 & 305,500 & 1.74 \\ Republic of Korea & 593,586 & 0.70 & 112,124 & 0.20 & 7952 & 0.08 & 442,046 & 2.52 \\ Iran & 505,000 & 0.59 & 449,950 & 0.80 & 55,050 & 0.53 & / & / \\ Cambodia & 305,408 & 0.36 & 291,738 & 0.52 & 1590 & 0.02 & 11,900 & 0.07 \\ Taiwan & 291,499 & 0.34 & 197,516 & 0.35 & 17,621 & 0.17 & 73,500 & 0.42 \\ Malaysia & 224,171 & 0.26 & 153,033 & 0.27 & 53,909 & 0.51 & 16,608 & 0.09 \\ Pakistan & 160,744 & 0.19 & 160,438 & 0.28 & 306 & 0.00 & / & / \\ Dem. & & & & & & & & \\ People’s & 76,560 & 0.09 & 13,995 & 0.02 & / & / & 62,400 & 0.36 \\ Rep. Korea & & & & & & & & \\ Sri Lanka & 33,841 & 0.04 & 27,448 & 0.05 & 6098 & 0.06 & 27 & 0.00 \\ Singapore & 5831 & 0.01 & 4708 & 0.01 & 195 & 0.00 & 15 & 0.00 \\ Hong Kong & 3787 & 0.00 & 3167 & 0.01 & / & / & 620 & 0.00 \\ SAR & 1500 & 0.00 & 1020 & 0.00 & 440 & 0.00 & 40 & 0.00 \\ Brunei & & & & & & & & \\ Darus-salam & 933 & 0.00 & 341 & 0.00 & 592 & 0.01 & 2 & 0.00 \\ Timor- & & & & & & & & \\ Leste & 120 & 0.00 & 119 & 0.00 & 1 & 0.00 & / & / \\ \hline
**ROI total** & (22 & **74,628,006** & **87.45** & **48,339,474** & **85.82** & **9,230,669** & **88.07** & **16,056,177** & **91.49** \\ countries) & & & & & & & & \\ Asia total & 75,435,608 & 88.40 & 49,082,188 & 87.14 & 9,321,341 & 88.93 & 16,060,694 & 91.51 \\ World total & 85,335,990 & 100.00 & 56,327,079 & 100.00 & 10,481,319 & 100.00 & 17,550,576 & 100.00 \\ \hline \hline \end{tabular} ROI: Region of interest (ROI) refers to all Asian countries, which cover the coastal zone of Asia (CZA); see Section 2. * excluding aquatic plants; Note: / represents lack of available data or the production volume is regarded as negligibly low.  
\end{table} 
Table 3: Aquaculture production (excluding aquatic plants) for all countries in the study region and respective shares of the main aquatic product groups in 2019. Data source: [1]. further developed and adopted. The most significant advancement is the integration of water coverage information derived from multispectral Sentinel-2 data. Figure 6 shows all relevant processing steps of the applied workflow in this study.