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Ph. D. candidate: Joseph, Xingang Zhou

Supervisor: Prof. Anthony G. O. YEH

Identifying Morphological and Functional City Centers

—a Mobile Phone Positioning Data Approach

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1. Introduction

2. Literature review

3. Aim and research questions

4. Research Design

5. Research Methodology

6. Conclusion

Outline

Identifying Morphological and Functional City Centers -

a Mobile Phone Positioning Data Approach

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1 Introduction

− The availability of mobile phone data has given a new momentum to explore urban structure and residents’ activities in a smart way (Batty et al., 2012)

− How to apply these new data to the urban planning theory is an essential problem to be explored

− Although the CBD is still the principal center in urban areas, population, jobs and employments have gradually centralized in a certain distance around the principal city centers. Their agglomeration has led to many sub-centers, which have great effects on urban spatial structure (McMillen and William Lester, 2003)

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2 Literature Review

Definition of sub-centers

Following population decentralization, urban workplaces tend to be decentralized. The employments are concentrated enough to qualify a district as a sub-center.

First, the workplaces density is significantly larger than areas around. Second, sub-centers should have multiple functions, including retailing, manufacturing and financial, and impact the urban structure in terms of population density and land prices. Third, sub-centers should be functionally connected with principal centers (McMillen and Smith, 2003).

The difficulty is to make the definition operational. How large is large? How to measure the impacts of sub-centers on urban structure?

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2 Literature Review

Identification of sub-centers

Many researchers identify sub-centers as employment density peaks among the urban area. (Giuliano and Small, 1991) used the Los Angeles as the study area, and defined a sub-center as an aggregated area that have at least 10 employments per acre and that together have at least 10,000 employees. McDonald (1987) defined a sub-center as a cluster of significant positive residuals from a simple regression of employment density with the distance from the CBD.

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2 Literature Review

Identification of sub-centers(McMillen, 2001) used a two-stage nonparametric estimation to identify sub-centers, and found that proximity to sub-centers plays an important role in employment density

The first step is to use a nonparametric estimator, locally weighted regression, to smooth employment density. The second step is to use a semiparametric regression to determine whether the potential subcenters have significant effects on employment density

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3 Aim and research questions

Aim:

Identifying Morphological and Functional City Centers

To explore urban spatial-temporal structure

The activity density analysis at different time of the day will help understand urban spatial structure, which is of great significance for urban planning and transport policy making

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3 Aim and research questions

• Research questions

• How to explain the variation of the population distributions in different parts of the city?

• Where are the morphological centers and functional centers?

• What is the general method for identifying city centers?

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4 Research Design

• Study area The study area is the urbanized area of one city in China (the city is anonymous here to protect the privacy of the mobile phone users)

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4 Research Design

• Data description

User ID Date Time Longitude Latitude

0032a435ce158d07 2457120039 114.21297 22.60739

00ce46a692154a1e 2456726001 114.38796 22.71257

01b6acc8fc1d7d89 2455688176 114.21297 22.60739

Sample records from the mobile phone dataset

− Mobile phone data

Spatial extent of the mobile phone towers

Spatial autocorrelation analysis

空间自相关分析（ spatial autocorrelation analysis）是一种检验具有空间位置的观测值是否与相邻空间位置上的观测值有显著关联的空间统计分析方法，用来评估所表达的模式是聚类模式、离散模式还是随机模式。

全局Moran指数反映整体的空间自相关强度

Spatial autocorrelation analysis

Local Moran’s I identifies statistically significant hot spots, cold spots, and spatial outliers

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• Identifying morphological city centers

5 Research Methodology

FAR (floor area ratio) of commercial and public facility land-use may be used as proxy to identify morphological city centers and sub-centers

The Municipal Building Survey (2009)

Building name, address, main function, number of storeys, and building footprint area

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• Kernel Density Estimation

5 Research Methodology

Kernel density estimation is used to transform the activity locations visited which are of point pattern to a continuous activity density surface (Kwan, 2000)Calculates a magnitude per unit area from point features using a kernel function to fit a smoothly tapered surface to each point使用核函数根据点要素计算每单位面积的量值以将各个点拟合为光滑锥状表面

http://meipokwan.org/Gallery/Density.htm

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• Identifying functional city centers

5 Research Methodology

Time-cumulative spatial activity density is used to understand the spatial distributions of intensity of various activity types

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5 Research Methodology

• Identifying functional city centers

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6 Conclusion

The city centers play important roles for residents’ activities. The city centers are

attractive not only for working and business during working hours, but also for

shopping and recreation at night.

城市中心在居民的日常活动中扮演重要的角色，不仅是居民就业活动的中心，同时也是晚上居民购物和休闲的重要场所

Thank you !

Q & A