# Mapping Areal Precipitation with Fusion Data by ANN Machine Learning in Sparse Gauged Region
## 3 Results and Discussion  
### Precision of Original TRMM Products  
#### 3.1.1 Grids with the Gauge Station  
According to the methods above, the precision criteria of original TRMM products on the 20 grids with the gauge station are shown in Table 1. The names of the gauge stations are LengHu (LH), XiaoZaoHuo (XZH), GeErMu (GEM), HeXi (HX), MangYa (MY), NuoMuHong (NMH), GeErMu4 (GEM4), DaChaDan (DCD), HuaiTouTaiLa (HTTL), GaHai (GH), NaChiTai (NCT), WuLan (WL), DeLingHa (DLH), DuLan (DL), ChaHanWuSu (CHWS), XiaRiHa (XRH), XiangRiDe (XRD), KeEr (KE), ShangGaBa (SGB), ChaHanHe (CHH), respectively. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**Gauges**} & \multicolumn{4}{c}{**Original 3B42 RT**} & \multicolumn{4}{c}{**Original 3B43**} \\ \hline
**No.** & **Name** & **X (°)** & **Y (°)** & **DEM** & **MAP** & **MAP** & **Bias** & **RMSD** & **MAP** & **Bias** & **RMSD** \\  & & & **(mm)** & **(mm)** & **(mm)** & **(mm)** & **(\%)** & **(mm)** & **(mm)** & **(\%)** & **(mm)** \\ \hline
1 & LH & 93.33 & 38.75 & 2777 & 19.88 & 41.10 & 106.79 & 23.17 & 36.19 & 82.07 & 18.42 \\
2 & XZH & 93.68 & 36.80 & 2772 & 30.34 & 81.60 & 168.97 & 57.76 & 77.49 & 155.44 & 52.74 \\
3 & GEM & 94.90 & 36.42 & 2812 & 47.32 & 126.01 & 166.30 & 81.28 & 113.31 & 139.46 & 68.68 \\
4 & HX & 94.60 & 36.38 & 2822 & 47.34 & 121.63 & 156.91 & 77.60 & 111.21 & 134.89 & 68.22 \\
5 & MY & 90.85 & 38.25 & 2942 & 50.16 & 68.37 & 34.55 & 26.85 & 60.59 & 19.79 & 20.07 \\
6 & NMH & 96.42 & 36.43 & 2796 & 55.54 & 118.66 & 113.65 & 67.30 & 117.21 & 111.05 & 65.48 \\
7 & GEM & 94.78 & 36.30 & 2957 & 61.76 & 126.01 & 104.05 & 67.61 & 113.31 & 83.48 & 55.44 \\
8 & DCD & 95.37 & 37.85 & 3190 & 104.00 & 122.89 & 18.17 & 38.35 & 119.28 & 14.69 & 28.18 \\
9 & HTTL & 96.73 & 37.35 & 2867 & 107.94 & 160.30 & 48.51 & 65.39 & 162.39 & 50.45 & 63.29 \\
10 & GH & 97.43 & 37.23 & 2877 & 161.24 & 157.18 & \(-\)252 & 32.02 & 168.12 & 4.27 & 26.18 \\
11 & NCT & 94.57 & 35.87 & 3966 & 182.31 & 230.40 & 26.38 & 70.91 & 222.21 & 21.89 & 65.31 \\
12 & WL & 98.48 & 36.92 & 2959 & 222.26 & 157.31 & \(-\)29.22 & 83.38 & 174.37 & \(-\)21.55 & 66.26 \\
13 & DLH & 97.37 & 37.37 & 2988 & 228.68 & 201.19 & \(-\)12.02 & 41.53 & 203.84 & \(-\)10.86 & 35.93 \\
14 & DL & 98.10 & 36.30 & 3190 & 240.73 & 183.92 & \(-\)23.60 & 73.11 & 195.62 & \(-\)18.74 & 58.43 \\
15 & CHWS & 98.12 & 36.23 & 3273 & 244.97 & 211.97 & \(-\)13.47 & 54.70 & 218.89 & \(-\)10.65 & 45.53 \\
16 & XRH & 98.15 & 36.42 & 3143 & 252.91 & 183.92 & \(-\)27.28 & 95.16 & 195.62 & \(-\)22.65 & 81.60 \\
17 & XRD & 97.87 & 35.97 & 3100 & 285.18 & 264.48 & \(-\)7.26 & 57.26 & 265.41 & \(-\)6.93 & 55.43 \\
18 & KE & 97.70 & 35.95 & 3269 & 307.43 & 278.26 & \(-\)9.49 & 70.71 & 277.94 & \(-\)9.59 & 70.63 \\
19 & SGB & 98.58 & 37.00 & 3168 & 332.05 & 170.04 & \(-\)48.79 & 171.22 & 187.25 & \(-\)43.61 & 151.87 \\
20 & CHH & 98.57 & 37.05 & 3351 & 432.30 & 257.26 & \(-\)40.49 & 189.76 & 258.21 & \(-\)40.20 & 187.08 \\ \hline \end{tabular}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multicolumn{2}{c}{-} & Average & – & – & – & 170.72 & 163.12 & 36.51 & 72.25 & 163.92 & 31.63 & 64.24 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The precision of original Tropical Precipitation Measurement Satellite (TRMM) products (2001–2016). LH: LengHu; XZH; XiaoZaoHuo; GEM: GeErMu; HX: HeXi; MY: MangYa; NMH: NuoMuHong; GEM4: GeErMu4; DCD: DaChaDan; HTTL: HuaiTouTaiLa; GH: GaHai; NCT: NaChiTai; WL: WuLan; DLH: DeLingHa; DL: DuLan; CHWS: ChaHanWuSu; XRH: XiaRiHa; XRD: XiangRiDe; KE:Er; SGB: ShangGaBa (SGB), CHHanHe; MAP: Mean Annual Precipitation. It is clear in Table 1 that the average mean annual precipitation (MAP) of 3B42 RT and 3B43 on the 20 grids are 163.12 mm and 163.92 mm, respectively, which look quite close to that of the gauged precipitation (170.72 mm). However, it can be found that the TRMM precipitation is higher in the low gauged precipitation areas (LGPA), including the stations of LH, XZH, GEM, HX, MY, NMH, GEM4, DCD and HTTL.