## 3 Materials and Methods
### Description of Infrastructure  
The existing monitoring localization systems for railway vehicles often combine GNSS technology with additional systems, e.g., balises (physical or virtual) or odometers, which make the train position more precise and can be used both on multirail tracks and for more precise localization. This article aims to introduce the available localization system for additional support of the dispatcher control based on the GNSS, focusing on regional and single tracks where a certain inaccuracy resulting from the GPS character can be accepted.  
The infrastructure of the Czech rail network currently covers over nine and half thousand kilometres of railway lines divided into four categories (Figure 1).  
* Corridor lines recorded in the European railway system with a total length of 1402 km (pink color);
* National lines recorded in the European railway system with a total length of 1189 km (green color);
* National lines not recorded in the European railway system with a total length of 3748 km (red color);
* Regional lines not recorded in the European railway system with a total length of 3232 km (blue color).  
Single tracks cover approximately 7607 km, which corresponds to a maximum of 80% of the total length. The regional lines cover over 33% of the tracks [28; 29].  
To build a railway network model, it is inevitable to have suitable data, enabling us to develop a model with a certain degree of abstraction. Experiments have show that a rail network model design can be based on hectometer posts. These devices are physical elements located in the railway infrastructure rail yard (at about 100 m distances). Each of them disposes of a GPS coordinator, among others. Data analysis provided by the Railway Infrastructure Management--Technical Center proved that the following four data tables are generally sufficient for a railway network model design:  
* The stationing and hectometric posts table and TUDU (track definition node);
* The supertrack table;
* The railway stations table;  
Figure 1: Railway line structure in the Czech Republic.  
* The definition suprasections table.  
The key connection element between individual tables is always the TUDU. We can say that individual supertracks consist of definition supra-sections, where each suprasection contains the track definition nodes (TUDUs) with hectometre posts. The basic aspects of a railway network description are described as a complex in Figure 2.  
The hectometer points in Figure 2 indicate the distance in kilometers, and they are marked as grey points in the graph. The TUDUs are recorded by six-digit codes (163105, 163106, 16307, and 173202) and by full lines in the graph (red, black, orange, and brown). Individual suprasections (CLS 007, CLS008, REG023) are marked with a light blue color, and the supertracks by interrupted lines. Significant traffic points (line branching) are marked with a green square.  
The above indicated way of viewing infrastructure relates to the situation in the Czech Republic; however, a same or similar attitude or its variations can be applied also outside the country because hectometer posts exist on tracks in many European countries.