The processing of measurement data from satellite
constellations such as Global Navigation Satellite Systems
(GNSS), including the well-known Global Positioning
System (GPS), have been successfully applied to virtually
all areas of geophysical sciences. In this work, a
method is described where Geographical Information Systems
(GIS) are employed to build hourly ionospheric Total
Electron Content (TEC) maps for 2011 over the southern
Iberian Peninsula. The maps used GPS-derived geometryfree
linear combinations attained from station data from
the Algarve, Alentejo (Portugal), Andalusia, Murcia and
Valencia (Spain) regions. Following the construction of
the ionospheric maps, it was possible to relate these results
to natural phenomena. The observed phenomena included
diurnal and seasonal variations: daytime TEC maxima,
nighttime TEC peaks, summer TEC value decreases,
and spring and fall TEC maxima. After validation of these
periodic phenomena, detection of non-periodic changes,
such as solar flares and tectonic interactions with the ionosphere
were attempted. The results showed a TEC increase
following a selected solar flare event and a potential TEC
build-up prior to the 2011 Lorca earthquake. Further studies
could open up the possibility of building early warning
systems. The presented methods, based on available software
packages, are also of value in monitoring the effect of
the ionosphere on radio signals, satellite and mobile communication,
power grids, and for accurate GNSS navigation