# The Use of Earth Observation Data for Railway Infrastructure Monitoring--A Review  
[PERSON]  
1 Faculty of Mechanical Engineering, University of Nis, 18000 Nis, Serbia; [EMAIL_ADDRESS] (M.M. ); [EMAIL_ADDRESS] (M.T. ); [EMAIL_ADDRESS] (M.S.) [PERSON]  
2 OHB Digital Services GmbH, 28399 Bremen, Germany; [EMAIL_ADDRESS] (D.R.-D.); [EMAIL_ADDRESS] (A.K.) [PERSON]  
1 Faculty of Mechanical Engineering, University of Nis, 18000 Nis, Serbia; [EMAIL_ADDRESS] (M.M. ); [EMAIL_ADDRESS] (M.T. ); [EMAIL_ADDRESS] (M.S.) [PERSON]  
2 OHB Digital Services GmbH, 28399 Bremen, Germany; [EMAIL_ADDRESS] (D.R.-D.); [EMAIL_ADDRESS] (A.K.) [PERSON]  
1 Faculty of Mechanical Engineering, University of Nis, 18000 Nis, Serbia; [EMAIL_ADDRESS] (M.M. ); [EMAIL_ADDRESS] (M.T. ); [EMAIL_ADDRESS] (M.S.) [PERSON]  
1 Faculty of Mechanical Engineering, University of Nis, 18000 Nis, Serbia; [EMAIL_ADDRESS] (M.M. ); [EMAIL_ADDRESS] (M.T. ); [EMAIL_ADDRESS] (M.S.) Szebcnyi St.l. durability, stability under dynamic conditions, energy efficiency, and mechanical performance, ultimately increasing the safety, reliability, and sustainability of global rail transport systems [1; 2; 3]. In parallel, there are increased efforts for improvements of reliability and efficiency of railway infrastructure monitoring to identify critical areas and to monitor the effects of maintenance measures. Traditional methods, such as manual inspections and track recording vehicles, are now complemented by innovative technologies like sensor networks, machine learning, and remote sensing [4; 5]. This paper explores Earth Observation (EO) satellite data as a relatively untapped resource for monitoring railway infrastructure that offers novel solutions to enhance safety, reliability, and efficiency in this sector, providing valuable insights into environmental factors affecting railway infrastructure. The use of satellite data in railways primarily involves data from Global Navigation Satellite System (GNSS) and EO data. GNSS, which is extensively documented, has significantly improved navigation and signalling, enabling precise train tracking and reduced reliance on trackside infrastructure, leading to cost savings and improved safety [6; 7; 8; 9], and is already considered as key for the rail sector digitalization [10]. In contrast, the application of EO data in this domain has been limited but is gradually gaining recognition for its potential to revolutionize railway monitoring [11]. EO satellites use sensors like optical cameras, radar (SAR), and infrared to collect images and measurements of land, oceans, and atmosphere and to provide advanced tools with a high potential for analyzing railway operations, identifying issues early, and optimizing maintenance strategies. By integrating EO data with AI, rail network management can be safer and more efficient [12]. Despite its growing usage, significant knowledge gaps remain, particularly in terms of using EO data for comprehensive railway infrastructure monitoring. Related review papers, such as those by [PERSON] et al. [13] and [PERSON] et al. [14], primarily focus on general infrastructure applications, with railways as a minor consideration. Railway-specific studies, such as [15], often limit their scope to synthetic aperture radar (SAR) data. Consequently, to the best of our knowledge, this review provides the first systematic overview of EO data applications specific to railway infrastructure, examining their use cases and the broader range of satellite technologies employed. Current EO applications for railway monitoring reveal several deficiencies. The predominant reliance on SAR data, while effective for deformation monitoring, overlooks the potential of optical, thermal, and multispectral EO data for a holistic analysis of railway systems [14; 15; 16]. Furthermore, limited data resolution and revisit times pose challenges for real-time monitoring, especially in dynamic environments where rapid response is critical [17].