VTEC maps over Europe during the 09/03/2012 (day of year 069) for the period 11:45–12:00 UTC. (a) Ionospheric models in NRT; (b) Previous 15 days median model; (c) Differences between (a) and (b); (d) histogram and statistics of the differences (http://gnss.be/Atmospheric_Maps/static_ionospheric_maps.php). The color bars in the center represent the VTEC in TECU and the ionospheric range error (L1) in m (top), as well as the difference between the current and the median VTEC values in TECU (bottom).