Sensing Human Society

Although the commercial use of cellular communications began as far back as 1983, owing to the high price of both the service and the devices used, it was limited primarily to business purposes. Cellular phone prices began to drop drastically in the mid-1990s, and today, in the developed world, cell phones are owned by people of all ages, professions, and income levels, with cell phone penetration in the developed world recently passing the 80% mark (Eurostat, 2005). In 2005 the United Kingdom had a 102% penetration rate, second only to Israel with a penetration rate of 106% and Sweden with a rate of 103% (World Bank, 2006). In recent years the penetration of this communications technology has accelerated also in many parts of the developing world. It is expected that, by 2010, more than 50% of the world's population will own a cellular phone, at which time we will be able to refer to human society as a whole as a cellular society. The operation of a cellular phone network requires the network operator to be able to constantly detect the subscriber's proximity to a specific antenna ( c̀ell'). This enables the operator to transmit incoming and outgoing calls to and from the user's handset. This feature allows the tracking of the device. However, it is clear that there are more accurate tracking technologies currently availableösuch as global positioning systems (GPS), for example (Shoval and Isaacson, 2006)öthat are increasingly being embedded into cell phones nowadays. The fact that an ever-increasing proportion of human society constantly carries a tracking device at all times and in all places creates new possibilities for spatial research. If all the phones that belong to the network are tracked at specific periods, cell phone location data can be used for the aggregative analysis of human activity, and, in practice, this enables the human sensing of entire populations. The application of this aggregative approach makes it possible to take a synoptic view of the time ^ space activity of hundreds of thousands of people in urban and metropolitan areas, or even the time ^ space activity of millions of people at a national level. This fact, coupled with the considerable progress in the field of GIS, currently places us on the verge of a veritable revolution in human time ^ space activity research.