Analysis of the ionospheric equivalent slab thickness based on ground-based GPS/TEC and GPS/COSMIC RO measurements

► Ionospheric slab thickness based on ground- and air-based GPS measurements has been analyzed. ► Diurnal variations of the slab thickness are generally characterized by higher values in nighttime. ► Pre-sunrise peaks of the slab thickness are observed for non-auroral latitudes in all seasons. ► Peaks of the slab thickness in mid-noon are detected near geomagnetic equator in all seasons. ► Diurnal ratios of the ionospheric slab thickness are highest in the EIA crests in winter.