The Basel watch show is taking place this week and while there are luxurius watches on display by Patek Philippe, Ulysse Nardin or Rolex there are also some technological innovations. This year it's GPS making its way to watches, at least to the surprising Citizen Appleseed that synchs to GPS satellite signals to adjust itself each day.
Using radio signals to adjust a watch is not new since Junghans launched the "Mega 1" in 1990. This type of watch is now common and they synch to the low frequency signals broadcast by base stations located in Europe, the USA and Japan but coverage is limited to these regions. What's new with the Appleseed is using GPS signals that have worldwide coverage. GPS watches already exist but they are large and their battery life is limited (the new stylish Nike+ TomTom watch claims 40 days though) as they need to synch to multiple satellites at the same time and decode their ephemeris data to calculate a fix. In addition GPS signals come from satellites placed in orbit at about 20,000kms and are very weak with a frequency of 1575Mhz that had little indoor penetration
Citizen must have found a way to work with the weak signals indoors and what must have helped is that to get just the time, only part of the signal of one single GPS satellite has to be decoded. Since Citizen use the "Ecodrive" (solar charging) the battery life is potentially unlimited.
Availability is announced for the fall so in the meantime we still have an exuse to be late ;-)