Comparison is made of topside equatorial parameters obtained from DMSP satellites with those measured from Jicamarca radar and those calculated from Another Model of the Ionosphere (SAMI2). To determine acceptable limits for this volume, knowledge of the spatial and temporal gradients in the parameters must be defined. Those can be obtained independently from each data source and are dependent on local time and season. Having described the spatial gradients, a comparison of the ionospheric variables can be made. The present study focuses on simultaneous ground-based and satellite data obtained for June 2002. Data for days 11, 12, and 13 are compared in this study. Satellite data are obtained from the DMSP satellites F13 (0600--1800 LT) and F15 (0900--2100 LT), respectively. Ground-based data are obtained from the Jicamarca radar. These are then compared with numerical computations performed by the SAMI2 model for the same period. Good agreement between observation and model is achieved for the total ion concentration during daytime and nighttime, while the ion and electron temperatures agree well at night. The light ion fraction is usually <20% from all three sources except during sunrise where the light ion content can be higher. Accounting for the variables H+ and He+ concentrations in the topside appears to be the major factor affecting the different data sources.