## 3 Materials and Methods  
### Overview of the Approach  
The proposed automation of registration is a multi-stage process; it is based on the original software and it consists of (1) data conversion to the raster form, (2) aligning of pairs of raster TLS data for all possible combinations based on SURF and FAST algorithms, (3) the analysis of the quality of relative orientation of processed pairs, and (4) the final bundle adjustment. The presented TLS data processing is an original approach. As a result of this process decision may be made whether the obtained results meet the assumed accuracy criteria or they are considered as an approximation of the ICP method. For that purpose, the original application, as well as external software tools (LupoScan3D (Pro 2018.2, Lupos3D, Berlin, Germany, 2018), ArcMap 10.2.2 (Esri, Redlands, CA, USA, 2014)) were applied. In order to perform a complete analysis of the possibilities for applying algorithms for detecting tie points on an intensity raster, the form of the point cloud transformation should be determined to obtain the best results. Verification of the following parameters was required. 1. The time of pre-processing of the RAW TLS data. 2. The time of detection of characteristic points. 3. The percentage of incorrectly detected points and adjusted characteristic points. 4. The completeness of data registration
5. The number of detected control and check points. 6. The orientation accuracy of control and natural and marked check points. 7. The distribution of control and check points. Then, it was possible to assess which method of point cloud representation allowed the highest accuracy to be obtained for TLS data. The diagram showing research work and experiments performed is presented in Figure 2.  
Point clouds acquired by Z + F 5003 and Z + F 5006h terrestrial laser scanners were stored in binary form. Binary files, contrary to simple text files, do not have a uniform structure and they cannot be processed directly. Thus, it was decided to use a temporary version of the Software Development Kit (SDK) of the Z + F scanner. Importing and conversion of TLS data were performed by means of the original application based on the SDK tools of the scanner. The idea of the automatic TLS data registration presented in this paper (according to the diagram presented in Figure 2) consists of the following stages:  
1. generation of intensity rasters in the spherical projection and orthoimages (with the depth map) using LupoScan and rasters in the Mercator projection and maps of XYZ coordinates in the original application and in ArcMap. 2. detection of characteristic points using the SURF (blob) and FAST (point) detectors on point clouds processed to the raster form in the spherical projection, in the Mercator projection and in orthoimages. generation of pairs of raster using the methods of permutations without repetitions \(\mathrm{C_{n}^{k}}=\left( \begin{array}{c}\mathrm{n}\\ \mathrm{k}\end{array} \right)=\frac{\mathrm{n!}}{\mathrm{E}(\mathrm{n-k})! }\), where: k = 2 (a pair of scans), n - the number of all scans-the spherical projection and the Mercator projection,  
2. generation of pairs of raster using the methods of permutations without repetitions \(\mathrm{l*C_{n}^{k}}=\left( \begin{array}{c}\mathrm{n}\\ \mathrm{k}\end{array} \right)=\frac{\mathrm{l*n!}}{\mathrm{E}(\mathrm{n-k})! }\), where: 1 - the number of planes (the number of walls, the ceiling, and the floor) k = 2 (a pair of scans), n - the number of all scans-orthoimages,the complete process of calculations was performed for all projections (2.1 and 2.2) using SURF and FAST algorithms.