## 2 Research Background  
The issue of parking-space-occupancy evaluation is currently a frequent subject of scientific analysis and study. It is part of the general scope of subjects related to intelligent  
Figure 1: An example of distributing cameras and lidars in a car park using the direct method. transport systems and technologies [4; 5; 6; 7], including image analysis [8]. This is a particularly important matter, as the increase in the number of cars (along with electric cars) results in longer search times for an available parking space, especially in city centers. For this reason, various concepts and technical solutions have been developed to determine the current number of vehicles in parking spaces, and thus inform subsequent drivers about the available number of parking spaces [9; 10; 11]. In one study, the authors elaborated on the analysis of the above mentioned areas [12]. They characterized in detail the currently used parking models, adopting four modeling approaches: mathematical, probabilistic, economic, and analytical. It is a useful review of the models, especially in the context of a further analysis of the estimation of the measurement uncertainty of the number of vehicles in a car park. The issue of the availability of parking spaces can be considered not only in terms of a given car park but also for a broader view, including car parks located in a specific area (e.g., district, city). In one of their publications, the authors of [13] presented such an approach. They used a hierarchical approach that supported drivers in locating a parking space in a car park free of charge. For this purpose, they used two levels of decision making. In the first level, the algorithm checked only the nearest car park. In the second level, the algorithm focused on the car park closest to the one checked and looked for an available parking space there. This solution was effective and saved drivers' time. Despite the positive outcome, the uncertainty regarding the number of available parking spaces in individual car parks was not taken into account. To identify available parking spaces in a car park, other authors proposed a measure based on the cooperation of drivers who reported available parking spaces [14]. In return, they received some type of bonus. This concept was based on a blockchain block solution. Information about beacons from parked vehicles was also used. The idea is interesting from a practical point of view. Still, it is difficult to assess its correct functioning at the present stage (especially for estimating the measurement uncertainty of the number of vehicles in a car park). In another study, the authors proposed using pressure sensors to determine the occupancy of parking spaces [15]. The designed system, thanks to the use of pressure sensors (detecting vehicles entering and leaving) and the Raspberry Pi, was characterized by low implementation and flexible adaptation to various car parks. This solution was interesting, but lacked an accurate evaluation method for the identification of entering vehicles. Thus, this method should be supplemented with data from a video monitoring system. This approach is presented in this article. Another way to estimate the occupancy of parking spaces was proposed by the next study's authors [16]. They used ultrasonic vehicle detection technology. The individual ultrasonic sensors were connected to a RS485 bus, which enabled data transmission to the parking management information technology (IT) system. As a result, drivers received information about the number of vacancies that they could then use. The article assessed the correctness of the system operation including, in particular, the correctness of the data from the ultrasonic sensor (the ambient temperature and the distance between the parked vehicle and the sensor were taken into account). Despite the proposed solution's practical implementation, it was expensive as it required wiring to connect the ultrasonic sensors.