## 7 Conclusions  
Considering that coordinate transformation represents a significant tool in the field of geodesy and geoinformatics, the aim of this article was to provide a closer explanation of all transformation models, with an emphasis on the process of determining transformation parameters, and, finally, calculating transformation parameters for all models with the example of the territory of the Republic of Croatia. In order to calculate transformation parameters, a set of 5000 identical points in the inherited HDKS system and the new HTRS96 system of the Republic of Croatia was used. Transformation parameters of all transformations and the corresponding external accuracy assessment are given in Table 9.  
Although transformation parameters are a crucial metadata for coordinate transformation, they alone are not sufficient for a unique implementation of the transformation. It is also important to know with respect to which convention they are calculated and which form of rotation matrix was used during their calculation. These data should be provided to users along with the transformation parameters in order to successfully perform a unambiguous coordinate transformation. If users, after performing the transformation, wish to return to the original coordinate system, they should use only one set of transformation parameters and the inverse form of the basic transformation expression instead of two sets of parameters.  
**Author Contributions:** Conceptualization, M.P.; methodology, T.B.; software,M.D.; validation, M.P. and A.B.; formal analysis, M.D. and T.B.; investigation, M.D. and T.B.; resources, M.P.; data curation, M.D. and T.B.; writing--original draft preparation, T.B.; writing--review and editing, M.P., M.D., and A.B.; visualization, T.B.; supervision, M.P. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The datasets presented in this article are not readily available because there are restrictions applied to the datasets due to copyright permissions of Croatian State Geodetic Administration.  
**Conflicts of Interest:** The authors declare no conflicts of interest.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Parameter** & **3p** & **5p Standard** & **5p Abridged** & **7p** & **8p** & **9p** & **12p** \\ \hline \(t_{x}\) (m) & 644.192 & 651.902 & 652.010 & 546.509 & 512.173 & 380.278 & 21.389 \\ \(t_{y}\) (m) & \(-213.131\) & \(-210.792\) & \(-210.746\) & 162.269 & 152.010 & 155.903 & 21.389 \\ \(t_{z}\) (m) & 442.788 & 497.803 & 497.354 & 469.395 & 529.617 & 653.169 & 21.389 \\ \(da\) (m) & - & 767.897 & 767.889 & - & - & - & - \\ \(df\) (\(c^{\prime}\)) & - & \(4.828\times 10^{-6}\) & \(4.890\times 10^{-6}\) & - & - & - & - \\ \(r_{x}\) (\(c^{\prime}\)) & - & - & - & \(-5.906\) & \(-5.587\) & \(-5.212\) & - \\ \(r_{y}\) (\(c^{\prime}\)) & - & - & - & \(-2.075\) & \(-3.129\) & \(-5.991\) & - \\ \(r_{z}\) (\(r^{\prime}\)) & - & - & - & \(11.507\) & \(11.510\) & \(12.003\) & - \\ \(u_{x}\) (ppm) & - & - & - & \(-4.418\) & \(-1.788\) & \(13.597\) & - \\ \(\mu_{y}\) (ppm) & - & - & - & - & \(-3.149\) & - \\ \(\mu_{z}\) (ppm) & - & - & - & - & \(-12.464\) & \(-26.094\) & - \\ \(u_{11}\) (\(\circ\)) & - & - & - & - & - & 0.999901 \\ \(u_{12}\) (\(\circ\)) & - & - & - & - & - & 0.0000241 \\ \(u_{13}\) (\(\circ\)) & - & - & - & - & - & - & 0.0000882 \\ \(u_{21}\) (\(\circ\)) & - & - & - & - & - & - & 0.000003 \\ \(u_{22}\) (\(\circ\)) & - & - & - & - & - & - & 0.0000352 \\ \(u_{31}\) (\(\circ\)) & - & - & - & - & - & - & -0.0000407 \\ \(u_{32}\) (\(\circ\)) & - & - & - & - & - & - & 0.0000218 \\ \(u_{33}\) (\(\circ\)) & - &