## 3 Results  
### Offsets Measurement  
Dimensional control of the survey boat and the offsets of measuring equipment on hydrographic boats was carried out in two stages. In the first stage, offsets were measured on the Hydrograf XXI boat, during which the Total Station-Terrestrial Laser Scanning (TLS) integrated survey method was tested. This method was tested due to the small size of the hydrographic boat, which meant that there was limited opportunity to select measurement stands for Total Station. In addition, Total Stations are generally limited in their ability to measure close points (less than 1 m) due to the problem of aiming and focusing on such a close target. Dual-purpose measurement targets were used to integrate Total Station measurement data with the point cloud from TLS (Figure 5). Tachymetric measurements were used as a reference for all measurements, to which laser scanning measurements were referenced. Tachymetric measurements were made using the technology of a (completely) free station--Total Free Station (TFS) [48; 49]. TFS measurements were made from two stations, each time without levelling the instrument (Total Station). The measurements were taken as random local datums and then combined into a sparse point cloud using transformation (5). The accuracy of the point clouds is shown in Table 2.  
Table 2 shows the point cloud accuracies after measuring offsets using the combined Total Station (TS) and TLS methods. The accuracy of the transformation of the tachymetric measurements to the combined point cloud was 1.4 mm, and the accuracy of the transformation of the TLS point cloud relative to the TS point cloud was 4.5 mm. This gives a total TLS cloud error of 4.7 mm, which is at the level of the point cloud density from terrestrial laser scanning. Taking this into account, the result of the transformation and the accuracy of the determination of offsets at the level of no worse than 5 mm was considered satisfactory. This type of survey on larger boats and ships does not impose restrictions on the use of Total Station, which occurs on small survey boats (instrument distance to measured point less than 1 m). It is therefore not necessary to supplement the measurements with additional TLS measurements and thus to combine data of different accuracies. In our study, this was necessary, and to increase the accuracy we used a coordinate transformation algorithm so that the combined point cloud from the Total Station and TLS measurements was at the level of accuracy of the Total Station measurement. This is especially true for points that are impossible to measure with Total Station. The next stage of the work involved dimensioning and measuring the offsets of the HYDROMAPPER boat. An electronic Total Station, Trimble SPS 930 (Trimble, Westminster, CO, USA), and two terrestrial laser scanners, Faro Focus 3D (FARO Technologies, Lake Mary, FL, USA) and Riegl ZF 5016 (RIEGL Laser Measurement Systems GmbH, Horn, Austria), were used for the measurements. A photogrammetric-geodetic (dual-function) warp was established to check the correctness and accuracy of the fit of the scans, which consisted of measurement discs that were measured with Total Station (Figure 2). The discs were visible on the scans and were used to orient the scans and check the accuracy of their fit. The coordinates of the control points are summarised in Table 3. The control points were measured in the local coordinate system, levelled with the measuring instrument (Total Station). \begin{table}
\begin{tabular}{c c c} \hline \multirow{2}{*}{**Accuracy Estimation**} & \multicolumn{2}{c}{**Coordinates’ Accuracy After Transformation [m]**} \\ \cline{2-3}  & **Calculated for Total Station** & **Calculated for TLS** \\  & **Point Cloud** & **Point Cloud** \\ \hline Mean error & \(1.4\times 10^{-3}\) & \(4.5\times 10^{-3}\) \\ Total error & \(1.4\times 10^{-3}\) & \(4.7\times 10^{-3}\) \\ (of point) & \(1.4\times 10^{-3}\) & \(4.7\times 10^{-3}\) \\ \hline \end{tabular}
\end{table}