Fig. 4From: Quasi-4-dimension ionospheric modeling and its application in PPPSeries of \({\sigma }_{i}\) in Eq. (9) for Q4DIM-2D TEC map of solution A (black) \(12\times 8\), solution B (red) \(24\times 16\), solution C (green) \(36\times 24\) and solution D (blue) \(48\times 32\) on DOY 001, 2020Back to article page