Plasmaspheric total electron content (PTEC) remains an elusive component of GPS TEC, even in middle latitude regions. PTEC is significant in measuring and modeling the ionosphere to altitudes much lower than GPS, such as for ground-based transionospheric radars that must detect and track orbital and ballistic objects. In addition, for GPS TEC observations to be useful for today's assimilative models, each TEC measurement needs to have an associated uncertainty. It is clearly beneficial if such uncertainty figures are not constant upper bounds, but rather are as data-specific and determined as possible. This paper presents results from a study using a chain of GPS stations on the west coast of North America. Ionospheric TEC, PTEC, and uncertainties are derived, and validated against Jason 1 TEC. We suggest that the methodology presented has potential to improve midlatitude ionospheric TEC accuracy for modeling, system impact and forecasting applications, and for monitoring PTEC.