Towards a Comparative Science of Cities: Using Mobile Traffic Records in New York, London, and Hong Kong - Computational Approaches for Urban Environments - page 354

calls, SMS, or even data transfers? How does the results compare between multiple
cities? What are the signatures of the mobile network usage in major US, European,
or Asian cities, and how do they compare?
This chapter takes advantage of an unprecedented multimodal collection of
counter data recording the number of calls, SMS, request, and data transfer resolved
both in time and space in three cities - New York, London, and Hong Kong - to
investigate such questions. After presenting the data in Sect. 15.2 , Sect. 15.3 will
investigate the spatial repartition of activity in these three cities. Then in Sect. 15.4 ,
we will focus on people's behavior by investigating the dynamics of the activities on
both a local and city scale. In Sect. 15.5 , we will show how we can use a clustering
algorithm to automatically detect and classify such patterns either within one city
or across all of them. Finally, we will discuss in Sect. 15.6 how our work can help
us understand the changing nature of modern cities and especially what common
features can be captured in the patterns of human behavior: in these global cities,
what is the respective influence of city-specific and global factors on human life?

15.2 Materials and Methods

15.2.1 Geographical Background

Figure 15.1 shows a map of the three cities studied in this chapter: New York,
London, and Hong Kong. Greater London is divided into 33 “district boroughs,”
the central ones being referred to as Inner London , while the peripheral ones are
referred to as Outer London . The historic heart of London, the City of London ,isa
major business and financial center, where many banking and insurance institution
headquarters are located. While the city has a low resident population (around
7,000), over 300,000 people commute and work there every day, mainly in the
financial service sector. New York is divided in 59 “community districts,” gathered
into five boroughs. The boroughs of Queens, Brooklyn, Staten Island, and Bronx
are mainly residential. Manhattan is a major financial and decision-making center
(the UN headquarters, Times Square, and the Empire State Building are located
there). It has also one of the highest population densities in the world, with around
27,000 residents per square kilometers. Finally, Hong Kong territory consists of 4
regions split into 18 districts. Due to the mountainous nature of its land, less than
25 % of Hong Kong's territory is urbanized: the urban development concentrates on
Kowloon peninsula, the northern edge of Hong Kong Island, and a few settlements
throughout the New Territories.
Overall, London, New York and Hong Kong are comparable in terms of size and
population density (see Table 15.1 ). They are also all Alpha cities according to the
GaWC nomenclature of world cities (Beaverstock et al. 1999 ) which ranks cities
based on their connections with others in domains such as business, finance, law,
media, art, fashion, research, technology, education, tourism, and entertainment. As
Alpha cities, they are more integrated within the global economy than any other city.