Ionospheric variability can have serious consequences for operational navigation systems that use GPS signals. Climatological models of the ionospheric electron density distribution do not have the fidelity and resolution to predict the occurrence of many of the most important features and the strongest ionospheric gradients. An alternative approach is to assimilate ionospheric measurements to produce regional or even global maps of the electron density distribution. In turn, these can be converted to total electron content (TEC) maps for particular applications. The assimilation of ionospheric data has developed to the point where three dimensional (3D) global maps of ionospheric electron density and TEC can be obtained routinely. In this paper, we describe high quality global maps of electron density distribution and TEC obtained using our IDA3D ionospheric data assimilation algorithm. A study of the October-November 2003 storm period illustrates the global coverage that can be achieved with ionospheric imaging, and permits study of the development of ionospheric enhancements and depletions during geomagnetic storms. One advantage of 3D imaging is that the vertical distribution of electron density and vertical gradients can be studied as well as the horizontal density distribution and gradients. An important feature that often develops over the United States during storms is an F-region ionospheric enhancement called the Storm Enhanced Density (SED). Associated with the SED are very large TEC values and sharp gradients that have application for GPS navigation and the FAA's Wide Area Augmentation System (WAAS). We show how both the horizontal and vertical structure can be mapped and characterized by the assimilation algorithm. In particular, we show that the peak height of the plasma associated with the SED often rises to 600 km altitude or greater. These results could be used to provide information to operational systems.