  The R-Mode system, an advanced terrestrial integrated navigation system, is
designed to address the vulnerabilities of global navigation satellite systems
(GNSS) and explore the potential of a complementary navigation system. This
study aims to enhance the accuracy of performance simulation for the medium
frequency (MF) R-Mode system by modeling the variance of time-of-arrival (TOA)
measurements based on actual data. Drawing inspiration from the method used to
calculate the standard deviation of time-of-reception (TOR) measurements in
Loran, we adapted and applied this approach to the MF R-Mode system. Data were
collected from transmitters in Palmi and Chungju, South Korea, and the
parameters for modeling the variance of TOA were estimated.
