# Geometric Processing and Accuracy Verification of Zhuhai-1 Hyperspectral Satellites
## 3 Results and Discussion  
### Study Areas and Data Sources  
Geometric calibration is the premise of high data quality and the basis for satellite on-orbit processing. The OHS image of the Hubei area (No. 2018-09-28-OHS-Hubei) obtained on 28 September 2018, was used for OHS geometric calibration. The image size was 15,168 \((5056\times 3)\times 8147\) pixels. As shown in Table 2, the calibration control data include DOM and Digital Elevation Model (DEM) data in the Hubei area. The DOM resolution of the Hubei area is 2 m, the plane precision is better than 4 m, the DEM resolution is 15 m, and the elevation accuracy is better than 5 m (1\(\sigma\)). The average elevation of the area is 264 m and the maximum height difference is 556 m. Thumbnails of the image and control data are shown in Figure 4.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{ID} & \multicolumn{3}{c}{**Imaging Angle (\({}^{\circ}\))**} & \multirow{2}{*}{**Imaging Time**} & \multirow{2}{*}{**Band**} \\ \cline{2-2} \cline{5-6}  & **Roll** & & & **Pitch** & **Yaw** & \\ \hline \multicolumn{6}{c}{**3.2. Geometric Calibration**} \\
2018-09-28-OHS-Hubei & \(\mathbf{-1.09}^{\circ}\) & \(0.00^{\circ}\) & \(3.18^{\circ}\) & **2018-09-28** & 1-32 \\ \hline \multicolumn{6}{c}{**3.3. Band-to-Band Registration Accuracy**} \\
2018-9-12-OHS-Beijing & \(\mathbf{-5.26}^{\circ}\) & \(0.00^{\circ}\) & \(2.81^{\circ}\) & **2018-09-12** & 1-32 \\
2018-8-5-OHS-Tianjing & \(\mathbf{-11.85}^{\circ}\) & \(0.00^{\circ}\) & \(2.72^{\circ}\) & **2018-08-05** & 1-32 \\
2018-10-10-OHS-Shandong & \(\mathbf{-1.26}^{\circ}\) & \(0.00^{\circ}\) & \(2.95^{\circ}\) & **2018-10-10** & 1-32 \\ \hline \multicolumn{6}{c}{**3.4. Interior Orientation Determination Accuracy Evaluation**} \\
2019-01-13-OHS-Neimeng & \(\mathbf{11.84}^{\circ}\) & \(0.00^{\circ}\) & \(2.72^{\circ}\) & **2019-01-13** & 15 \\
2019-01-17-OHS-Henan & \(\mathbf{2.94}^{\circ}\) & \(0.00^{\circ}\) & \(3.00^{\circ}\) & **2019-01-17** & 15 \\
2019-01-24-OHS-Hebei & \(\mathbf{-0.50}^{\circ}\) & \(0.01^{\circ}\) & \(2.90^{\circ}\) & **2019-01-24** & 15 \\ \hline \multicolumn{6}{c}{**3.5. Block Adjustment**} \\
2018-08-12-OHS-Shanxi & \(\mathbf{8.64}^{\circ}\) & \(0.00^{\circ}\) & \(2.93^{\circ}\) & **2018-08-12** & 15 \\
2018-11-21-OHS-Shanxi & \(\mathbf{-8.69}^{\circ}\) & \(0.00^{\circ}\) & \(2.78^{\circ}\) & **2018-11-21** & 15 \\
2018-09-07-OHS-Shanxi & \(\mathbf{3.52}^{\circ}\) & \(0.00^{\circ}\) & \(2.79^{\circ}\) & **2018-09-07** & 15 \\
2018-11-19-OHS-Shanxi & \(\mathbf{9.82}^{\circ}\) & \(0.00^{\circ}\) & \(2.65^{\circ}\) & **2018-11-19** & 15 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Imaging information of experimental data.  
To fully verify the accuracy of the basic products after OHS geometric calibration, the spectral segment registration, single-view orientation, and regional adjustment accuracy of the product were evaluated. Three scene images obtained on 12 September 2018, 5 August 2018, and 10 October 2018, in Beijing, Tianjin, and Shandong, respectively, were used for accuracy evaluation of the spectral band registration. For the single-view orientation accuracy assessment, images obtained on 13 January 2019 and 17 January 2019 were collected. Also, three scene images obtained on 24 January 2019 are shown from Inner Mongolia, Henan and Hebei, respectively. DOM and DEM data were used for verification control of the corresponding area. The DOM resolution is 2 m, the plane precision is 5 m, the DEM resolution is 15 m, and the elevation accuracy is 3 m. Thumbnails of the experimental data and control data are shown in Figure 5, Figure 6, and Figure 7 for the different areas. Four-track 221-view basic product images covering Shanxi (12 August 2018, 21 January 2011, 7 September 2018, and 19 November 2018) were collected for regional adjustment accuracy assessment. The details of the calibration and verification data are shown in Table 2.  
Figure 4: Hubei regional geometric calibration image and control data.  
Figure 5: Neimeng regional control and verification data.