## 5 Discussion  
This paper deals with the possibility and reliability of the TLS method for surveying of the RK. We expect the following benefits for our practice from our approach. TLS method is a fast, accurate, and reliable method to acquire a large amount of spatial data about the surveyed object's large range. All in-situ TLS measurements of the selected RK were made within 5 h. About 22 million points from 4 stations were surveyed. For the proposed TLS method, it is also preferred that the measurement can be performed safely from the station on the ground, and also, several mutually registered stations of scanners can be applied. The whole measurement was taken during a service shutdown of the RK in cold status. In comparison with the traditional method of measurement, the advantage of this method is that the sequential rotation of the RK is not necessary. As a most significant disadvantage of the TLS method, we consider especially the fact that in most cases, it is impossible to survey the entire body of RK (for example, the axes of radial rollers or the whole shell of the kiln) because of the complex shape of the RK and permanent obstacles.  
The accuracy of TS measurements results from the accuracy analysis according to Equations (2) and (3). Therefore, it can be considered as a reference and control methods of measurement for our new approach. The accuracy of the reference methods meets technical standards requirements--for example [56; 57], local methodological guidelines, and the practical approach according to, for example, [31; 32; 33; 34; 35; 36]. The TLS data's direct control consisted of measuring 203 points on the kiln shell, approximately in its middle part. Then, the distances of the measured TS points to the point cloud obtained by TLS were compared. RMSD determined in CloudCompare software has a value of 2 mm, which we consider a successful control of measurement's selected technology.  
In TLS measurements, the results can also be affected by the scans' mutual registration. Our direct field registration approach allows the first quality control of measurements directly in the field by determining the RMSD of the position and height of each temporary survey station. In our case, these values were up to 2 mm, which corresponds to the expectations according to the parameters of the used instruments [54; 55]. Similar scan registration results were achieved also by, for example, [18; 11; 38].  
Figure 32: Longitudinal cross-section of the axis of the RK.  
The proposed analytical solution results for point cloud segmentation using frequency histograms in selected intervals of the body radius were verified against the basic approach--i.e., manual segmentation.  
TLS measurement is fast, but the data processing is significantly slower. The most time-consuming part of the data processing phase is removing the maximum number of unnecessary points and keeping the maximum of the next processing's important ones. Just an effort to save time and automate the process of segmentation in the point cloud was our motivation for the analytical solutions for point cloud processing. Based on our results, we can recommend our proposed point cloud segmentation process, especially for similar cylindrical bodies.