Comparing the IFRM estimates provided by TECOR, RMextract, ALBUS, and spinifex for the D2 observation. Left panel: for the VLA “D2' observation on 2023 November 4. The ALBUS values, in magenta, are an excellent match to the observed IFRM values. All models based on global VTEC estimates overcorrect the IFRM by 0.5–1.0 rad m⁻². Right panel: for the MeerKAT observation on 2025 August 18. The observed IFRM is in magenta, the G01-sutm estimate is in blue. All models based on VTEC maps again overestimate the IFRM, although by less than for the VLA: about −0.3rad m⁻².