I was running tonight and my iphone endomondo track put me on top of the Schuman EU Building; not completely accurate and typical of urban canyons phenomenon. This reminded me that accuracy of GPS signals is can be very relative. The systems can even be seriously hampered when solar storms occur. On the website gps.gov a lot of info can be found related to the fact that in 2013 period solar storms will be at their peak period The advice of the US government even mentions "GPS users should keep this in mind and always have a secondary means of navigation or timing." So time to buy a paper map? Not really, but the land based correction mechanisms (RTK part of GNSS) will become more important for landing airplanes correctly etc...In Belgium the full 3 networks ( Flepos in Flemish area, Walcors in Walloon area, GPSBru in Brussels) Seems that more and more commercial applications are turning to these geodetic solutions: will network configurations be able to keep up