## 3 Results
### Calculating the a Priori Accuracy Parameters for the Block  
The RMSE was calculated separately for the GCPs and CPs to evaluate the results' horizontal and vertical accuracy. Table 6 shows the values obtained in processing the four scenarios, the GSD, and the reprojection error.  
Equation (1) was applied to determine the estimation of the a priori horizontal error of the block; as the block size increases, the number of GCP at the edges should increase. Six strips were made for each block to cover the studied area. For the a priori vertical error, Equation (3) was used with the focal length equalling 15 mm.  
To determine the best a priori accuracy calculation equation for photogrammetry with digital sensors, Equations (5) and (6) values for \(\mu_{\mathrm{xy}}\) and \(\mu_{\mathrm{z}}\) were obtained for the four proposed scenarios, as shown in Table 7. These values can be compared in Scenarios A and C, as suggested by the authors [45].  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Scenario**} & **GSD** & **Reproj.** & **RMSE** & **RMSE** & **RMSE** & **RMSE** & **RMSE** & **CP\({}_{\mathrm{xy}}\)/** & **CP\({}_{\mathrm{x}}\)/** & **CP\({}_{\mathrm{xy}}\)/** \\  & **[cm]** & **Error** & **GCP\({}_{\mathrm{xy}}\)** & **CP\({}_{\mathrm{xy}}\)** & **GCP\({}_{\mathrm{z}}\)** & **CP\({}_{\mathrm{z}}\)** & **GCP\({}_{\mathrm{xyz}}\)** & **CP\({}_{\mathrm{xyz}}\)** & **CP\({}_{\mathrm{xyz}}\)** & **GSD** & **GSD** & **GSD** \\ \hline A & 2.7 & 0.3 & 0.3 & 4.8 & 2 & 10.7 & 2.0 & 11.7 & 1.8 & 4.0 & 4.3 \\ B & 2.7 & 0.4 & 0.7 & 4.6 & 2.3 & 6.8 & 2.4 & 8.2 & 1.7 & 2.5 & 3.0 \\ C & 2.7 & 0.4 & 0.3 & 4.5 & 1 & 9.9 & 1.0 & 10.9 & 1.7 & 3.7 & 4.0 \\ D & 2.7 & 0.5 & 0.9 & 5.3 & 2 & 10.9 & 2.1 & 11.0 & 2.0 & 3.5 & 4.1 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Parameters of the RMSE GCPs and CPs (in cm), using PIX4 Dmapper for the four scenarios studied, marking best results (green) and worst (red).  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Scenario**} & **Focal** & **Principal** & **Principal** & & & & & & \\  & **Parameters** & **Length** & **Point x** & **Point y** & **R1** & **R2** & **R3** & **T1** & **T2** & **Result 1** \\  & **[pix]** & **[pix]** & **[pix]** & **[pix]** & & & & & & \\ \hline \multirow{4}{*}{B} & Initial Values & 4559.840 & 2643.290 & 1912.470 & \(-\)0.005 & 0.009 & \(-\)0.008 & \(-\)0.001 & 0.004 & \multirow{4}{*}{0.34\%} \\  & Optimised Values & 4554.479 & 2640.732 & 1916.975 & \(-\)0.005 & 0.01 & \(-\)0.009 & \(-\)0.001 & 0.001 & \multirow{4}{*}{0.34\%} \\  & Uncertainties & 0.718 & 0.111 & 0.745 & 0.000 & 0.000 & 0.000 & 0.000 & 0.000 & & \\  & (Sigma) & 4564.399 & 2698.159 & 1910.765 & \(-\)0.004 & \(-\)0.043 & 0.087 & \(-\)0.003 & 0.004 & \multirow{4}{*}{3.30\%} \\ C & Optimised Values & 4725.975 & 2638.960 & 1945.875 & \(-\)0.006 & 0.014 & \(-\)0.015 & \(-\)0.001 & 0.001 & & \\  & Uncertainties & 14.225 & 0.484 & 1.421 & 0.000 & 0.000 & 0.001 & 0.000 & 0.000 & & \\  & (Sigma) & 4564.399 & 2698.159 & 1910.765 & \(-\)0.004 & \(-\)0.043 & 0.087 & \(-\)0.003 & 0.004 & \multirow{4}{*}{0.16\%} \\ D & Optimised Values & 4560.586 & 2642.156 & 1910.781 & \(-\)0.005 & 0.007 & \(-\)0.005 & \(-\)0.001 & 0.001 & & \\  & Uncertainties & 0.714 & 0.116 & 0.752 & 0.000 & 0.000 & 0.000 & 0.000 & 0.000 & & \\  & (Sigma) & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 5: _Cont._