## 1 Introduction
### Implementation of BIM Standards in the Czech Republic  
The introduction of BIM in the Czech Republic was legislatively launched by the Resolution of the Government of the Czech Republic No. 958/2016 on the importance of the BIM method for construction practice in the Czech Republic. The Ministry of Industry and Trade was entrusted by the Government of the Czech Republic with the implementation of BIM, which developed through the Czech Agency for Standardization the Concept of BIM implementation in the Czech Republic [1]. In the Ministry of Transport, the guarantor of BIM implementation is the State Fund for Transport Infrastructure, which developed the Prescription for Building Information Modelling (BIM) of Transport Infrastructure [6].  
The Railway Administration implemented the introduction of BIM technology into its organization with the document Strategy for the implementation of the BIM process with the assumption that it would play the role of data manager in the BIM process [7]. Currently, the documentation of railway infrastructure is heterogeneous and consists of about 65% of data in digital form and about 35% of data in analogue form. The aim is to unify the availability of data through a common data environment with efficient tools for data management and updating.  
BIM data must be highly standardized, especially for the usability of machine-readable exchange formats that are used to update BIM data during the operation phase of the construction. Therefore, it is necessary to emphasize the standardization of the format and the standardization of the data contents.  
Format standardization at the international level in the field of BIM is addressed by the IFC (Industry Foundation Classes) standard, which is already implemented in the CSN standards. The IFC format serves as an interchange format between different BIM software.  
Contents standardization is about using the so-called LOIN (Level of Information Need). A BIM model contains geometric and non-geometric data and therefore two levels of detail (LOD) are distinguished, namely the Level of Detail of Geometry (LOG) and the Level of Information (LOI).  
BIM models must be georeferenced in a binding geodetic coordinate and height reference system because the compatibility with the cadastre data maintained in the Information System of the Cadastre of Real Estate must be ensured due to the property law aspect. In the Czech Republic, this is in the Datum of Uniform Trigonometric Cadastral Network (S-JTSK) and in the Baltic Vertical Datum--After Adjustment (Bpv). The Unified Geodetic Reference System must be correctly implemented in the BIM software. Cartesian coordinate systems in BIM or CAD software are mathematically right-handed, while geodetic systems are mathematically left-handed. Therefore, when the coordinate systems differ, the geometric data must be transformed into the BIM environment. Another specific feature of the BIM environment is the modelling of elevations. The geodetic height reference system and the position coordinate system do not form a Cartesian coordinate system together. Problems arising from this will become apparent in largescale constructions. The designer designs the building objects into a geodetic datum whose dimensions are converted into zero elevation and the corresponding cartographic representation of the geodetic reference system. Particularly in the case of projects for long sections of transport structures, the problem of distortion of dimensions is significantly manifested. Therefore, it is also necessary to take this into account in the BIM environment. The problem of georeferencing a BIM model in IFC format can be found, for example, in [8; 9].