Method of transmitting data of a railway communication system comprising a supervision data analysis unit, and at least one pair of communication devices comprising a static communication device (10, 11, 12), located on or in the vicinity of a railway track (101, 102, 103), the static communication device being an access point to the railway communication network, and a mobile communication device, located on a mobile railway vehicle, each communication device (10, 11, 12, 1001) being identified by an identifier and comprising a data processing unit, the communication devices (10, 11, 12, 1001) and the data analysis unit being connected to a communication network, the method of transmitting data being implemented by the data processing unit of a measurement communication device of said at least one pair of communication devices, and comprising the following steps: - when the static communication device and the mobile communication device of said at least one pair of communication devices are within emission range, determination, by the measurement communication device, of a power level of the signal emitted by a measured communication device corresponding to the other communication device, separate from the measurement communication device, of said pair of communication devices, - formation of mobile data comprising the power level of the emitted signal, the identifier of the measured communication device, and the identifier of the measurement communication device, - transmission of the mobile data to the data analysis unit, and when said measurement communication device is static and when said railway communication system comprises at least one other static communication device within emission range of the static measurement communication device, the method of transmitting supervision data, implemented by the measurement communication device comprises in addition the following steps: - periodic calculation, by the measurement communication device, of a sliding average of a power level of the signal emitted by said at least one other static communication device over a predetermined temporal window, - formation of static data comprising the sliding average, the identifier of said at least one other static communication device, and the identifier of the measurement communication device, - transmission of the static data to the data analysis unit. - when the static communication device and the mobile communication device of said at least one pair of communication devices are within emission range, determination, by the measurement communication device, of a power level of the signal emitted by a measured communication device corresponding to the other communication device, separate from the measurement communication device, of said pair of communication devices, - formation of mobile data comprising the power level of the emitted signal, the identifier of the measured communication device, and the identifier of the measurement communication device, - transmission of the mobile data to the data analysis unit, - periodic calculation, by the measurement communication device, of a sliding average of a power level of the signal emitted by said at least one other static communication device over a predetermined temporal window, - formation of static data comprising the sliding average, the identifier of said at least one other static communication device, and the identifier of the measurement communication device, - transmission of the static data to the data analysis unit.