## 4 Results
### The Number of Points Detected on Raster Images  
The following coefficients were verified for the requirements of the assessment of the number of detected points for all pairs of raster images (from all projections): The average, the maximum and the minimum number of detected and matched key points (characteristic points) (Table 3) and the percentage of incorrectly detected and matched key points (characteristic points) (Table 4). Statistical data was developed with the use of the original application in Matlab software. The statistics presented in Table 3 show the detector effectiveness (statistics of numbers of detected points) on the different test sites in each of the three cartographic transformations. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{3}{*}{**Detector**} & \multicolumn{6}{c}{**Average Computation Time [Minutes \& Seconds]**} \\ \cline{2-7}  & \multicolumn{3}{c}{**Test Site I**} & \multicolumn{3}{c}{**Test Site II**} \\ \cline{2-7}  & \multicolumn{3}{c}{Cartographic transformation} \\ \cline{2-7}  & Spherical & Orthoimage & Mercator & Spherical & Orthoimage & Mercator \\ \hline FAST & 0\&17 & 1\&0 & 1\&44 & 4\&2 & 1\&1 & 3\&31 \\ SURF & 7\&15 & 0\&14 & 4\&10 & 8\&57 & 2\&5 & 6\&10 \\ \hline \multicolumn{7}{c}{**Test site III**} & \multicolumn{6}{c}{**Test site IV**} \\ \hline FAST & 0\&13 & 0\&4 & 1\&38 & 0\&11 & 0\&3 & 1\&6 \\ SURF & 0\&43 & 0\&2 & 1\&55 & 8\&50 & 0\&6 & 4\&50 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Time for detection and matching of characteristic points for particular projections of point clouds, for test sites I and II (both scenarios). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{3}{*}{**Statistic**} & \multirow{3}{*}{**Detector**} & \multicolumn{6}{c}{**Statistics of Number of Detected and Matched Keypoints**} \\ \cline{3-8}  & & \multicolumn{3}{c}{**Test Site I**} & \multicolumn{3}{c}{**Test Site II**} \\ \cline{3-8}  & & \multicolumn{3}{c}{Cartographic transformation} \\ \cline{3-8}  & & Spherical & Orthoimage & Mercator & Spherical & Orthoimage & Mercator \\ \hline \multirow{3}{*}{**Avg**} & FAST & 3614 & 5676 & 1961 & 9150 & 16764 & 1808 \\  & SURF & 3023 & 7466 & 2200 & 10153 & 6525 & 8516 \\ \hline \multirow{3}{*}{**Min**} & FAST & 1944 & 2954 & 785 & 599 & 289 & 378 \\  & SURF & 1626 & 2087 & 461 & 1103 & 2610 & 1617 \\ \hline \multirow{3}{*}{**Max**} & FAST & 8314 & 12774 & 3420 & 44813 & 44138 & 101975 \\  & SURF & 4644 & 19254 & 7634 & 44813 & 11251 & 31914 \\ \hline \multirow{3}{*}{**Statistic**} & \multirow{3}{*}{**Detector**} & \multicolumn{6}{c}{**Test Site III**} & \multicolumn{6}{c}{**Test Site IV**} \\ \cline{3-8}  & & \multicolumn{6}{c}{Cartographic transformation} \\ \cline{3-8}  & & Spherical & Orthoimage & Mercator & Spherical & Orthoimage & Mercator \\ \hline \multirow{3}{*}{**Avg**} & FAST & 426 & 159 & 202 & 35 & 44 & 17 \\  & SURF & 244 & 83 & 304 & 36 & 12 & 20 \\ \hline \multirow{3}{*}{**Min**} & FAST & 111 & 30 & 22 & 13 & 13 & - \\  & SURF & 16 & 8 & 10 & 13 & - & - \\ \hline \multirow{3}{*}{**Max**} & FAST & 1615 & 965 & 1228 & 99 & 99 & - \\  & SURF & 1608 & 194 & 1390 & 99 & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Statistics of number of detected and matched keypoints for particular projections of point clouds for all test sites (both scenarios). The analyses performed for test site I show that, on average, the minimum and maximum numbers of points (for all pairs of scans) were detected using FAST and SURF detectors, respectively, for scans in the spherical projection, using FAST and SURF detectors in the case of orthoimages and using SURF and FAST detectors for the Mercator projection. The largest number of corresponding points was obtained for the SURF detector with the use of spherical images. Based on the analysis of data acquired from test site II, it may be stated that the highest numbers of tie points were detected using the FAST detector for raster images in the Mercator projection, orthoimages and spherical images.