An invaluable time series of the ionosphere's Total Electron Content (TEC) is available thanks to the Topex/Poseidon and Jason missions. Unlike sun-synchronous altimeters, these missions can be used to map daily harmonics of TEC, much like is done for ocean tides. Of special interest is TEC variability at n cycles/day, their seasonal variability, and their dependence on solar fluxes. A recent comprehensive paper by Lean et al. (2016) explored much of this material by using TEC data determined from the global network of GNSS stations. I discuss the kinds of high-wavenumber errors that occur in these GPS products, which nadir altimeters are particularly good at highlighting. The implications of relying on GNSS-based TEC data to correct for path delay -- now done routinely for single-frequency altimeters -- will be explored. Errors directly impacting determination of ocean tides are most obvious.