## 3 Results
### Comparison of GIS vs. BIM Remodelling Options  
The need to rework existing CAD building documentation into BIM or GIS stems from the current needs of large building managers, given that the building was originally designed in CAD and was not previously documented in either a BIM or GIS environment. The fundamental need is to use as much information as possible from the construction documents corrected to the as-built state, including ensuring its effective accessibility, which can be addressed through BIM or GIS. When comparing the two ways of remodelling CAD documentation into BIM and GIS, it is important to stress that both approaches share a common basis, i.e., the creation of objects to which descriptive information is linked. However, the two approaches differ in the detail of the geometric information. For the purpose of maintenance of the building during its lifetime, it is also advisable to consider the degree of simplification of the documentation, or the possibility of using schematization with appropriate linking to the archive of the execution documentation. The BIM model is in 3D and thus more detailed, so it detects potential height collisions much better. In GIS, height collisions have to be resolved by analyzing the drawing in the context of attribute-resolved levels, which is less convenient. Another advantage of the BIM model is the possibility of using models of prefabricated parts, which can be easily imported into the BIM model, when modelling building structures. With regard to the documents used for the design, it must be considered that BIM or GIS models must be compatible in particular with cadastral data and therefore it is necessary to respect the relevant national geodetic reference system, which is defined by \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Relationship** & \
\begin{tabular}{c} **Number of** \\ **Elements** \\ \end{tabular} & **Percent** &
\begin{tabular}{c} **Example of** \\ **Element** \\ \end{tabular} & **Description** \\ \hline
1 to 1 & 10 & 25 & tracked & one RA standard element corresponds to one BIM standard element \\ N to 1 & 16 & 40 & culvert & multiple RA standard elements correspond to one BIM standard element \\
1 to N & 2 & 5 & bridge & one RA standard element corresponds to multiple BIM standard elements \\ N to N & 1 & 2.5 & platform & more RA standard elements correspond to more BIM standard elements \\  & 6 & 15 & shaft & RA standard element can be incorporated into a similar BIM standard element based on experience \\  & 5 & 12.5 & building & RA standard element is addressed by a different regulation \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of elements of the RA standard and the BIM standard. the reference surface and map projection, for their correct geographical location. A specific feature of BIM or GIS models of linear structures is the distortion of the model resulting from the geodetic reference system used. In terms of georeferencing, this functionality is not completely standard in current BIM software. In the case of the Bentley ProjectWise CDE environment used, the geographic coordinate system parameters of the model can be taken from the initial import of the model data. In the GIS model, georeferencing is solved quite standardly by assigning the appropriate national geodetic reference system, but it is necessary to change the dimension to a 2D model with database information, or to use tools to support a 3D BIM model placed in the GIS scene. The need to use 2D or 2.5D GIS results from the need for compatibility with the DTM CZ established by legislative regulation [3]. The ESRI ArcGIS Pro platform offers support for accessing BIM data through the Industry Foundation Classes (IFC) format as well as the Revit Project File (RVT) format. This allows you to view all the details, textures and information for individual objects, but without the ability to edit or modify the appearance or structure.