Precision and safety-critical Global Navigation Satellite System (GNSS) applications require high-fidelity monitoring of space weather conditions, particularly ionospheric disturbances. These systems are highly sensitive to sharp spatial gradients and rapid Total Electron Content (TEC) variations. To support both operational and scientific needs, this study proposes and evaluates two variants of the Gradient Ionosphere indeX (...

Spaceborne GNSS reflectometry (GNSS-R) has emerged as a valuable technique for surface and atmospheric remote sensing, particularly under grazing-angle geometries where atmospheric effects are amplified. Single-frequency missions such as ESA passive REflecTomeTry and dosimetrY (PRETTY) rely on model-based corrections to account for ionospheric and tropospheric delays. In this study, we exploit PRETTY’s capabilities to perform...

Ionospheric tomography offers three-dimensional (3D) description of the electron density distribution, enabling the direct incorporation of electron density data into the slant total electron content (STEC) computation. As a result, STEC derived from tomography helps mitigate the ionospheric delay experienced in the line of sight between global navigation satellite systems (GNSS) and satellites positioned in low Earth orbits (...

Ionospheric indices give information about ionospheric perturbations, which may cause absorption, diffraction, refraction, and scattering of radio signals, including those from global navigation satellite systems (GNSS). Therefore, there may be a relationship between index values and GNSS positioning results. A thorough understanding of ionospheric indices and their relationship to positioning results can help monitor and fore...

To aid single-frequency GNSS users, the Neustrelitz Total Electron Content Model (NTCM) has been proposed as an adequate solution to mitigate propagation errors besides the GPS Klobuchar and Galileo NeQuick models. Using the three effective ionization coefficients broadcast in the Galileo navigation message as driver parameters, the version NTCM-GlAzpar, in general, performs equal to or better than NeQuickG when compared to th...

The differential code biases (DCBs) of the global positioning system (GPS) receiver onboard low-Earth orbit (LEO) satellites are commonly estimated by a local spherical symmetry assumption together with the known GPS satellite DCBs from ground-based observations. Nowadays, more and more LEO satellites are equipped with GPS receivers for precise orbit determination, which provides a unique chance to estimate both satellite and...