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Ionospheric threats generated during storms included in the IOC threat model (i.e., delay fit residuals |I¯−I∼| that violate the inequality in Equation (2)), binned as a function of fit radius R_fit and the delay fit residual: (a) threat counts without data deprivation, (b) threat counts with data deprivation

Distribution of fit IPPs in the epoch on November 20, 2003, that generates a critical point at R_fit = 1450 and RCM = 0.575 in the tabulation of the disturbed-time branch of the ionospheric threat model: (a) all measurement IPPs in the epoch, (b) the IPPs that remain in the domain after directional station deprivation has been applied to remove the 12 most northeastern stations In each plot, X marks the location of the IGP in whose threat domain (indicated in red) the IPP responsible for the critical point (pictured in Figure 3(a) but not Figure 3(b)) is located. The fit domain centered on the IGP is indicated by the dashed line in Figure 3(b).

Quiet-time branch of the spatial–temporal ionospheric threat model when the tabulation of the Release 46-CY16 threat model is augmented by storm data from solar cycle 24 during 2011–2015: (a) threat model raw data, (b) threat model overbound

Directional station deprivation in a network configuration consisting of the 25 IOC WAAS stations (i.e., the first 25 stations listed in Table A1 of Sparks et al. (2026)) The depicted mask removes from fits of vertical delay the measurements recorded by receivers at the 12 most northeastern WAAS stations (in red). Data recorded at the station in Honolulu (black triangle) are ignored as well.

Release 51-CY18 spatial–temporal ionospheric threat model: (a) quiet-time raw data, (b) quiet-time overbound, (c) disturbed-time raw data, (d) disturbed-time overbound

LPV Release 6/7 spatial–temporal ionospheric threat model: (a) threat model raw data, (b) threat model overbound

Schematic diagram illustrating how vertical delay is estimated throughout the construction of the ionospheric threat model A delay estimate is evaluated at each IPP that lies within the threat domain surrounding a given IGP. Estimates are achieved by fitting all of the measured values of slant delay, converted to vertical delay, whose IPPs are located in a fit domain defined by a circle of radius R_fit centered on the IGP.

LPV Release 8/9.2 spatial–temporal ionospheric threat model: (a) threat model raw data, (b) threat model overbound