## 4 Assessment of the Developed Approach
### Assessment of Structural Element Reconstruction
#### 4.3.1 Inspection of Reconstructed Walls  
The results of 3D semi-automatic reconstruction of walls and slabs are shown Figure 14 for both datasets. For visualisation purposes exploded perspective views are used. For the individual house 44 objects were created (12 walls and 32 portions of walls) whereas for office building 127 objects were created (35 walls and 92 portions of walls). For both datasets, about a third of wall portions corresponds to indoor parts of facades since the approach considers indoor point clouds exclusively. A visual inspection of the results superimposed with input indoor point clouds allowed to determine that 93% of acquired objects were reconstructed automatically for the individual house and 94% for the office building.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Ceilings and Grounds**} & **Walls** & **Objects** \\ \hline \multirow{4}{*}{**Individual house**} & TP & 99\% & 89\% & 94\% \\  & FP & 1\% & 11\% & 6\% \\  & FN & 3\% & 1\% & 21\% \\  & Precision & 99\% & 89\% & 94\% \\  & Recall & 97\% & 99\% & 82\% \\ \hline \multirow{4}{*}{**Office building**} & TP & 99.5\% & 93\% & 81\% \\  & FP & 0.5\% & 7\% & 19\% \\ \cline{1-1}  & FN & 4.5\% & 9\% & 8\% \\ \cline{1-1}  & Precision & 99.5\% & 93\% & 81\% \\ \cline{1-1}  & Recall & 96\% & 91\% & 91\% \\ \hline \hline \end{tabular}
\end{table}
Table 3: Assessment of point classification into several categories.  
In order to assess the geometric quality of the reconstruction, deliverables created manually based on indoor point clouds of the buildings were exploited. For each floor of the buildings, a 3D rigid body transformation was performed so that floor plan extracted from the results of the 3D automatic reconstruction can be superposed to floor plan created manually. For that purpose, control points corresponding to points in common between the two plans were selected. Table 4 presents the minimum, the maximum and the mean of the 2D deviations observed for these control points for each floor of the two buildings. Deviations of one millimetre to several centimetres are observed between control points selected in floor plans created manually and automatically. Moreover, for all floors the mean of deviations is lower than 2 cm.  
Based on the superimposition of floor plans created manually and automatically, a visual inspection was performed to check if objects correctly describe the buildings. This inspection shows that 93% of objects are correctly placed for the individual house whereas 88% of objects are correctly placed for the office building. The falsely placed objects are mostly portions of facade walls. Figure 15 presents an example of the inspection of reconstructed walls for the 2 nd floor of the office building. The floor plan was extracted from a building information model constructed manually based on point clouds. Reconstructed walls and portions of walls are presented in red in the figure and points used for the calculation of the 3D rigid body transformation are in green.  
\begin{table}
\begin{tabular}{c c c c c} \hline  & \multicolumn{1}{c}{**Number of Points**} & \multicolumn{1}{c}{**Mean of Deviations**} & \multicolumn{1}{c}{**Minimum**} & \multicolumn{1}{c}{**Maximum**} \\  & & **Points** & **(cm)** & **Deviation (cm)** & **Deviation (cm)** \\ \hline
**Individual** & Garden level & 34 & \(1.1\pm 0.8\) & 0.2 & 4.4 \\
**house** & 1 st floor & 23 & 0.9 \(\pm\) 0.6 & 0.2 & 2.3 \\ \hline  & Ground floor & 20 & \(1.1\pm 0.6\) & 0.4 & 2.7 \\
**Office** & 1 st floor & 24 & \(1.2\pm 0.9\) & 0.1 & 3.7 \\
**building** & 2 nd floor & 32 & \(1.7\pm 1\) & 0.6 & 4.1 \\  & 3 rd floor & 10 & \(1\pm 0.6\) & 0.1 & 1.8 \\ \hline \end{tabular}
\end{table}
Table 4: Deviations between control points selected in floor plans created manually and automatically.  
Figure 14: Results of the 3D reconstruction of walls and slabs in an exploded perspective view.