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The global ionospheric total electron content maps (GIMs) provide integrated electron densities between the ground and the GPS satellite altitude (20,200 km). Satellite altimeter ionospheric delay corrections require integrated electron densities between the ground and altimeter satellite altitude. In the case of the Geosat Follow-On (GFO) spacecraft, flying at 800 km, we estimated that using GIM TEC data alone, up to a 2 cm path delay can be introduced into the GFO measurements for high solar activity period by not taking into account the electron content above this altitude. Furthermore, the GIMs can have errors of 20–30 TECU in low latitudes for high solar activity in areas where there is little GPS data (such as over the oceans). In this paper, we describe the results of ingesting GIM TEC data into the International Reference Ionosphere model (IRI-95) to mitigate these two effects.