NEDAM, or the Neustrelitz Electron Density Assimilation Model, is a four-dimensional variational assimilation scheme developed to retrieve electron density distributions from GNSS observations, demonstrating enhanced accuracy and performance in ionospheric modelling. NEDAM (Neustrelitz Electron Density Assimilation Model) emerges as a crucial tool in understanding the impact of the ionosphere on Global Navigation Satellite System (GNSS) signals. Validation through a European ground-based GNSS network and comparison with ionosondes and COSMIC-1 radio occultation observations during a geomagnetic storm period showcase NEDAM's superior accuracy. Particularly noteworthy is its improved precision in determining the critical frequency of the F2 layer compared to physics-based models, leading to enhanced reliability, even during storm conditions. NEDAM's ability to reconstruct both the peak density and its height sets it apart, addressing a critical aspect that was previously missing in research efforts.
