Radio occultation measurements performed by the satellites CHAMP, GRACE and FORMOSAT-3/COSMIC provide a huge data set for atmospheric and ionospheric investigations on a global scale. The data sets are used to extract information on sporadic <i>E</i> layers appearing in the lower ionospheric <i>E</i> region. This is done by analyzing signal amplitude variations of the GPS <i>L</i><sub>1</sub> signal. Sporadic <i>E</i> altitudes in northern midlatitudes found from radio occultation measurements are compared with ground-based ionosonde soundings. A large correlation of sporadic <i>E</i> altitudes from these two techniques is found.