The Earth's ionosphere and plasmasphere is a solar-ionized region in the upper regions of the atmosphere. It extends from the D-region, at 60km, into the lower magnetosphere. The region, driven by solar activity and storms, acts as a dispersive medium which introduces both astrometric errors at very low (meter-length) wavelength radio light, as well as the Faraday Rotation of linearly-polarized radio light when coupled with the Earth’s strong magnetic fields. This rotation can be tens of degrees in the linear angle of polarization below the S-band (~2.0 GHz). We explored the use of RINEX interchange data from the GNSS receivers on the South African TrigNET network (which forms part of the International GNSS Service) and parametric profiles of the ionosphere (PIM, developed originally by the United States Air Force) to measure the amount of Faraday rotation induced by the ionosphere. We verify our measurements with long-term monitoring of the (stable) linearly-polarized quasar, 3C286, as well as the limb of the Moon as part of a larger joint-calibrator study between the Very Large Array (Socorro, NM, USA) and MeerKAT (Carnarvon, Northern Cape, South Africa) interferometers. We find a residual scatter in the predicted RM values of about 1 radian per meter squared at the Karoo site, which is consistent with scatter using the most accurate distributed IONEX models from the international geo and space sciences communities (NASA CDDIS-distributed JPL, CODE and UQRG models). This poster highlights the necessity of more research in the area of accurate ionospheric modeling, especially in southern geomagnetic latitudes and its implications for low-frequency full polarization science in the Square Kilometer Array and ngVLA era.