InSAR time-series, designed to efficiently analyze data and detect structural instabilities in railway networks. This approach was validated across the entire railway network of the Netherlands, utilizing 213 Radarsat-2 acquisitions from 2010 to 2015. Over 3000 km of railway sections were analyzed, marking the first nationwide satellite-based application for railway monitoring. One of the main benefits of the InSAR remote sensing technique is that measurements of targets can be made repeatedly over large regions more effectively than traditional geodetic terrestrial measurement techniques such as levelling and theodolite. Terrestrial levelling measurements in the field and Global Navigation Satellite Systems (GNSSs) are highly precise in estimating the rate of subsidence along transportation lines but time-consuming and expensive when considering hundreds of kilometers of railways. In addition, InSAR eliminates the need to close down the railway for traffic and enables the collection of a significant amount of information that is transmitted regularly and on schedule. In recent years, a great deal of research has been performed on ground displacement, with a focus on linear-shaped infrastructures like railways and highways. These studies aim to monitor a range of factors, such as the structural strength and deformation of the rail [4; 5; 6; 7; 8; 9; 10; 11; 12; 13], assess the impact of tectonic and seismic movement on the rail [14], and determine the effect of ground subsidence caused by extraction of groundwater and human activity on the rail [15; 16; 17]. Radar interferometry has been utilized in the following ways: Small BAseline Subsets (SBAS) [14; 17; 18], Persistent Scatterer Synthetic Aperture Radar Interferometry (PS-InSAR) [3; 6; 7; 8; 9; 12; 19; 20; 21; 22; 23] and Differential Interferometric SAR (DInSAR) [24]. Long-term monitoring of the geological and geomorphological conditions surrounding the railway is important to ensure its safe and normal operation and to prevent fatal events and financial losses [10; 12; 25]. In some of these studies, geodetic methods such as ground levelling, GNSS and LiDAR were added to the SAR dataset(s), but no study comparing the InSAR method with the diagnostic train has been conducted so far. Therefore, the most important contribution and originality of this study is to include and use the diagnostic train in comparative analyses and to share the results. In addition, this work presents a unique study methodology by focusing only on railways, emphasizing the difference in the structure and the importance of observation precision. The diagnostic train measures, along with InSAR, have been utilized to monitor certain parts of a high-speed railway line between the capital of Ankara and Konya in Turkiye. The diagnostic train data assessed in this study pertain to the Roger-800 model train, and it conducts regular geometric measurements of the railway lines. Additionally, this diagnostic train is capable of performing point deformation measurements using a laser beam source on the rails at intervals of 25 cm. The levelling measurements collected from the train are used to examine the engineering health state of the lines. This allows the engineers of railway administration to carry out maintenance or repair activities, as well as prepare for future actions. For these reasons, this study is based on data acquired from the diagnostic train as the reference measurement system. Although there is a focus on collecting frequent measurement data, it is important to note that the current method can only collect data from the line approximately once every three months. This means that it cannot perform measurements at a high frequency, observe its surroundings and detect rapidly developing subsidence events. Hence, it is advisable to contemplate employing an alternative monitoring technique that may offer more frequent and reliable data, regardless of weather conditions and without the need for personal field visits.