Xintao Liu

The Hong Kong Polytechnic University | PolyU · Department of Land Surveying and Geo-Informatics

As the threat of urban heat island effect on human health continues to escalate, discussions on how to use landscape vegetation to mitigate high temperatures and improve outdoor thermal comfort have become important research topics. Although existing studies have explored the relationship between urban greenery and outdoor jogging activities, they...

Flooding caused by extreme climate change is becoming increasingly severe, especially in high-density coastal areas worldwide. Although many studies have conducted risk assessments of urban floods, most have not formed a comprehensive evacuation plan considering population distribution and flood disaster risk. To further enhance urban flood plannin...

This dataset provides a comprehensive analysis of urban population density and polycentricity dynamics across Chinese cities from 2001 to 2021. The data are meticulously collected and processed to reflect the evolution of subcenters within metropolitan areas, capturing changes in spatial structure and population distribution over two decades. Each...

Enhancing urban inclusivity is a crucial task for sustainable urban development. One key challenge is to create seamless and accessible urban space that caters to the mobility needs of people, especially the elderly. Addressing this pressing challenge requires a comprehensive overview of barrier-free facilities (BFFs) configuration within cities. I...

As technological advancements continue to blur the boundaries between cyber and physical spaces, individuals' activities are not limited to physical space and increasingly transcend singular space. Prior research on interactions between cyber and physical spaces oversimplified or even overlooked the interactions between the two spaces due to limite...

Amid rising mobility services in cities, the logistics sector plays a crucial role in envisioning daily services for local neighborhoods. Previous research has primarily identified key freight areas (KFAs) in small-scale regions using traditional census and travel survey data. However, differing from KFAs, other areas with distinct freight patterns...

In recent decades, our society has witnessed significant advancements in information and communication technologies (ICT), leading to the creation of cyberspace, also known as virtual space. Within this digital landscape, social media has emerged as a crucial component of cyberspace, with the ability to both reflect and profoundly influence our phy...

Insufficient urban parking in densely populated cities has led to challenges like traffic congestion and unauthorized parking. While existing literature extensively covers parking behaviors among private vehicles and taxis for commuters, limited research has been proposed centering on urban shared freight activities. It can be problematic to neglec...

Climate change has significantly increased the risks associated with urban flooding. However, most research on flood risk assessment focuses on large-scale climate changes and impacts, leaving a research gap in the high spatial resolution of flood risk assessment in inter-urban areas. This gap makes it difficult to guide regional planning for the g...

The development of Information and Communication Technology has shifted human activity from offline to online, and promoted digital economy. These changes challenge traditional methodologies relying on physical human activity as a micro-level reflection of the macro-level economy. To address this, a hierarchical framework is proposed to characteriz...

Urban sustainability has long been a major theme of city planning and development that seeks to optimize the socioeconomic and environmental circumstances to enhance the living environment for residents. It underlines that cities are complex urban systems shaped by a wide range of human activities and built environments, thus suggesting the necessi...

This paper brings a comprehensive systematic review of the application of geospatial artificial intelligence (GeoAI) in quantitative human geography studies, including the subdomains of cultural, economic, political, historical, urban, population, social, health, rural, regional, tourism, behavioural, environmental and transport geography. In this...

As urbanization accelerates, cities become more complex, coming along with more complex urban issues. Agent-based model (ABM) is a traditional method to simulate activities in a complex system, which has been widely applied in urban studies. However, due to its rigid initial settings, ABM has been criticized for its lack of intelligence, especially...

Superspreading events underscore the uneven distribution of COVID-19 transmission among individuals and locations. These heterogeneous transmission patterns could stem from human mobility, yet the underlying mechanisms are still not fully understood. Here, we employ an agent-based model incorporating urban scaling structure to simulate fine-grained...

The demands of socioeconomic development frequently lead to large-scale population migration among cities. While complex network and population migration algorithms have been employed to evaluate this phenomenon, predicting the future shift of urban networks has remained challenging. In this study, we expend the conventional two-dimensional percept...

The nighttime thermal environment affects people's nighttime leisure activities and energy consumption. While increasing studies have examined the interplay between urban morphologies and daytime temperature, a gap exists in understanding the nonlinear relationship in the nighttime thermal environment. To address this, the study employs a data-driv...

Transit-oriented development (TOD) aims to create pedestrian-friendly neighborhoods around transit hubs to improve urban mobility. However, it often overlooks the specific transportation needs of people with limited mobility. This study adopts Sen’s capabilities approach (CA) and the concept of conversion factors to analyze how ordinary pedestrians...

In recent decades, Digital transformation has significantly shifted human activities from physical space to cyber space. When users access the internet, uniform resource locator (URL) data are autogenerated. Using URLs, this study presents a novel framework for exploring cyber space structure from the perspectives of complex networks and activity f...

There has been growing interest in understanding how industrial variation and locational preferences are connected in recent years. However, little research has focused on the geographic disparities of industrial activities within megacities in terms of their spatial and functional variations. This study aims to addresses this issue by examining in...

Destination, as a key concept in tourism geography, has largely determined the scale at which tourist activity space was modeled and studied. Existing studies usually focused on investigating tourists’ activities and movements either at the intradestination (e.g., within a city) or interdestination scale. Although useful in numerous research contex...

Although shared e-scooters have displayed both complementary and competitive relationships with public transport, less attention has been paid to investigating the spatiotemporal variations of such relationships, and how the relationships are associated with the urban built environment. To bridge the gaps, we first explore the spatiotemporal hetero...

With the growth in the vehicle industry, autonomous driving has become a hot topic worldwide and has attracted increasing attention from both industrial and academic sectors. Maps, as pivotal geospatial information carriers, play a vital role in route planning and navigation service. Compared with conventional maps, high-definition (HD) maps posses...

Compared with administrative cities, natural cities can be generally referred to as the areas generated based on the density of different urban facilities (e.g., point of interest, road network, etc.). To some extent, natural cities are outperformed in some related urban studies, such as urban living structure analysis. Nevertheless, traditional wa...

Spatial morphology of 2D space has been well studied at the scales of building, community, and city in space syntax literature. Space syntax decomposes continuous geographic space into a set of unique axial lines and represents them as a spatial network to analyze spatial morphology. However, 3D spatial morphology remains largely unexplored, partia...

The Covid-19 pandemic has received immeasurable research attention across various scientific fields. We would argue that viewing Covid-19 through the lens of geography and urban analytics plays an essential role in interdisciplinary endeavors to understand and fight the pandemic. First, geographic location and time are the fundamental elements in t...

In recent decades, we have witnessed great advances on the Internet of Things, mobile devices, sensor-based systems, and resulting big data infrastructures, which have gradually, yet fundamentally influenced the way people interact with and in the digital and physical world. Many human activities now not only operate in geographical (physical) spac...

Household size and its spatial distributions reflect not only the socioeconomic development in a city but also the rationality of urban resource allocation. Most existing studies rely heavily on census data to explore the potentially influential factors using methods such as macro-statistical analysis and socioeconomic analysis, of which the spatia...

In recent years, shared freight systems have emerged in many cities as a new modality of freight transportation. However, little attention has been paid to the impact of a city’s socioeconomic status on the characteristics of a shared freight network. To fill this gap, in this study, the structural characteristics of an intra-urban shared freight n...

Agglomeration economies have been an increasingly prevalent interest in research communities of regional and urban studies. Recent evidence reports the importance of agglomeration economies closely associated with the urban network. However, limited efforts have been proposed to emphasize the spatial-functional roles of regional agglomeration and t...

Polycentric urban structures determine the combination and correlation of urban resources. In the past, nighttime light data was often used to identify the center locations, but the borders of polycentric urban regions (PURs) could not be obtained. Using multi-source remote sensing data and graph, this research proposes an effective method for poly...

Urban life involves a large variety of urban functions and human activities in a dense context due to the inherent nature of cities. Although technical frameworks have been previously proposed to understand urban functions and activities, there are limited studies that concern the individual places within a city and their detailed characteristics a...

This paper presents a proof-of-concept designer-in-the-loop schematic map drawing tool, based on the marriage of two approaches – manual and automated, which provides the technical interactivity of drawing tools between the user and the computer. We focus on concentric circle maps as opposed to the commonly used orthogonal mode representation, whic...

The specialization of different urban sectors, theories, and technologies and their confluence in city development have led to a greatly accelerated growth in urban informatics, the transdisciplinary field for understanding and developing the city through new information technologies. While this young and highly promising field has attracted multip...

In this workshop, we will attempt to challenge the current paradigm of cartography or GIScience, by advocating a new mapping paradigm. We will use the two concepts – natural cities and natural streets – to demonstrate the ubiquity of living structure and Scaling Law, and further demonstrate the automatic generation of all small-scale databases from...

In this study, we draw upon the concept of ‘activity space’ rooted in human geography and apply it in a contemporary urban context—Macao. Noting the growing trend of urbanisation and the blurring boundary of tourist-resident spaces, this research systematically analysed the mapping and structure of tourist and resident activity spaces and interpret...

Classification of land use and land cover from remote sensing images has been widely used in natural resources and urban information management. The variability and complex background of land use in high-resolution imagery poses greater challenges for remote sensing semantic segmentation. To obtain multi-scale semantic information and improve the c...

A surge in public demand has led to the increasing popularity of personalized mapping, and the automated construction of map symbols has been playing a key role its facilitation. Although several studies on map symbols (e.g., on the design of map symbols and explorations of the usability of map symbols) have been conducted, automated construction o...

Since the first confirmed case was reported in January 2020, Hong Kong has experienced multiple waves of COVID-19 outbreaks. Recent literature has explored the spatial patterns of disease incidence and their relationships with the built environment and demographic characteristics. Nonetheless, few studies aim at the comparative patterns of differen...

Three-dimensional transportation space is one of the most important characteristics of multi-layered cities; however, fine-scale built environment factors about facilities that support the 3D walking environment were unavailable in understanding travelers’ behaviors before heading to the Big Data era. Using both small (questionnaire survey) and big...

Although E-scooter sharing has become increasingly attractive, little attention has been paid to a comprehensive comparison of e-scooter sharing mobility in multiple cities. To fill this gap, we conduct a comparative study to reveal the similarity and differences of e-scooter sharing mobility by collecting and analyzing vehicle availability data fr...

Accessibility and mobility are positioned differently at the heart of transportation planning; whist a transportation system with high accessibility is not necessarily be able to support high mobility. In this short article, we evaluate and visualize the accessibility and mobility of pedestrian networks around the metro station areas in a transit-o...

Environmental exposure of people plays an important role in assessing the quality of human life. The most existing methods that estimate the environmental exposure either focus on the individual level or do not consider human mobility. This paper adopts a vector field generated from the observed locations of human activities to model the environmen...

Industrial agglomeration is a concentration phenomenon of economic activities in cities. In recent years, the geographic and functional structures of industries are constantly changing due to global industrialization and regional urbanization. Thus far, a scarcity of research has investigated spatial-functional organizations of sectoral industries...

The strategies using transit-oriented development (TOD) to optimize transportation sustainability have been implemented in many metropolitan areas and extended beyond the role of exclusively offering transit services. Research findings from existing literature have largely shown that metro station catchment areas can attract a substantial number of...

High-resolution nighttime light (NTL) satellite images are needed for monitoring human activities and socioeconomic dynamics at fine scales, but such NTL data are very limited. On June 11, 2021, China launched the Yangwang-1 (“Look Up 1”) satellite, which is a small optical space telescope that detects near-earth asteroids, but its visible band sen...

Since the first confirmed case reported in January 2020, Hong Kong has experienced four waves of COVID-19 epidemic outbreaks. Recent research has inspected the spatial patterns of disease incidence and the associated built environment and demographic characteristics but rarely focused on the differences between two wave epidemics. In this study, we...

Relationship between urban diversity and urban vitality is imperative for guiding better design in urban development, though existing frameworks are not able to efficiently examine the relationship at multiple scales. In this article, we propose a new framework to integrate nighttime light (NTL) imagery and multisource urban data into multiscale ge...

The increasing availability of location-acquisition technologies has enabled collecting large-scale spatiotemporal trajectories, from which we can derive semantic information in urban environments, including location, time, direction, speed, and point of interest. Such semantic information can give us a semantic interpretation of movement behaviors...

In this era of population aging, it is essential to understand the spatial distribution patterns of the elderly. Based on the smart card data of the elderly, this study aims to detect home location and examine the spatial distribution patterns of the elderly cardholders in Beijing. A framework is proposed including three methods. First, a rule-base...

Modeling bicycle traffic assignment requires consideration of the various factors and criteria that could play a role in a cyclist’s route decision‐making process. However, existing studies on bicycle route choice analysis tend to overlook the less tangible or measurable aspects of cyclist route decision‐making, such as a cyclist’s cognitive unders...

Agglomeration economies have become commonplace globally as a means to promote productivity advantages in cities. Despite that previous studies have examined external determinants such as input resource, labor pooling, and knowledge spillovers, a small portion of literature aims at emphasizing the impacts from local contexts. This research therefor...

With the COVID-19 vaccination widely implemented in most countries, propelled by the need to revive the tourism economy, there is a growing prospect for relieving the social distancing regulation and reopening borders in tourism-oriented countries and regions. The need incentivizes stakeholders to develop border control strategies that fully evalua...

With the COVID-19 vaccination widely implemented in most countries, propelled by the need to revive the tourism economy, there is a growing prospect for relieving the social distancing regulation and reopening borders in tourism-oriented countries and regions. This need incentivizes stakeholders to develop border control strategies that fully evalu...

City service demand fluctuates across space and time. Although various data, such as 311 hotline data and social media data, have been used to explore the spatiotemporal patterns of city services, data uncertainty and the uneven distribution of service demand are overlooked to some extent and thus could result in bias. To overcome these shortcoming...

Developing data-driven approaches to understanding urban structures is important for urban planning. However, it is still challenging to combine different transport datasets into a unified framework and reveal the dynamics of urban structures with the emergence of shared mobility. In this study, we propose two empirical multilayer networks to infer...

A robust bus transit network is of fundamental importance for sustainable development by alleviating urban problems. This paper aims to explore the robustness of 57 bus transit networks from the aspect of transferability. Bus transit networks are constructed using open-source data from the same data source for ensuring a consistent comparison, and...

A city is a complex system that never sleeps; it constantly changes, and its internal mobility (people, vehicles, goods, information, etc.) continues to accelerate and intensify. These changes and mobility vary in terms of the attributes of the city, such as space, time and cultural affiliation, which characterise to some extent how the city functi...

Revealing urban functions in cities can be an essential means to describe the characteristics of human activities and places. Through the lens of points of interest and tourist online reviews collected in downtown Hong Kong, this study develops a semantic-based framework to detect and compare urban functional identities. The findings depict a uniq...

The COVID-19 outbreak has necessitated a critical review of urban transportation and its role in society against the backdrop of an exogenous shock. This article extends the transportation literature regarding community responses to the COVID-19 pandemic and what lessons can be obtained from the case of Hong Kong in 2020. Individual behavior and co...

Urban agglomeration is an important strategy used to promote economic development and urbanization in China. Understanding the structure of urban agglomeration is therefore essential for policy makers and planners. In this study, the Beijing-Tianjin-Hebei urban agglomeration (BTHUG) is explored through a proposed spatial network analytical framewor...

The measurement of medical service accessibility is typically based on driving or Euclidean distance. However, in most non-emergency cases, public transport is the travel mode used by the public to access medical services. Yet there has been little evaluation of the public transport system-based inequality of medical service accessibility. This wor...

Many studies have evaluated the influence of the built environment on public transport. Some studies assign subjective weights to environmental factors, which could oversimplify spatial heterogeneity and overlook the temporal dimension. On the other hand, the spatial-interaction network of public transport system is seldom considered. In this paper...

Many cities around the world face the challenge of an aging population. A full understanding of the mobility behavior characteristics of the elderly is one necessary and urgent consideration as regards the current aging trend if sustainable urban development is to be fully realized. This paper presents a systematic approach to analyzing the dynamic...

A group event such as human and traffic congestion can be very roughly divided into three stages: converging stage before congestion, gathered stage when congestion happens, and dispersing stage that congestion disappears. It is of great interest in modeling and identifying converging behaviors before gathered events actually happen, which helps to...

Earthquakes are one of the destructive natural disasters. Immediate emergency response in the first few hours is important for life rescue. The near real-time ground deformation maps generated after earthquakes are crucial for hazard assessments, which normally take a couple of hours or longer to be generated using conventional ways. In this study,...

Sensitivity analysis (SA) has been used to evaluate the behavior and quality of environmental models by estimating the contributions of potential uncertainty sources to quantities of interest (QoI) in the model output. Although there is an increasing literature on applying SA in environmental modeling, a pragmatic and specific framework for spatial...

In prior research, a statistically cheap method was developed to monitor transportation network performance by using only a few groups of agents without having to forecast the population flows. The current study validates this "multi-agent inverse optimization" method using taxi GPS trajectories data from the city of Wuhan, China. Using a controlle...

Received signal strength indicator (RSSI)-based positioning is suitable for large-scale applications due to its advantages of low cost and high accuracy. However, it suffers from low stability because RSSI is easily blocked and easily interfered with by objects and environmental effects. Therefore, this paper proposed a tri-partition RSSI classific...

Urban functional area (UFA) recognition is one of the most important strategies for achieving sustainable city development. As remote-sensing and social-sensing data sources have increasingly become available, UFA recognition has received a significant amount of attention. Research on UFA recognition that uses a single dataset suffers from a low up...

Understanding cab drivers' stay activities is essential for planning and managing certain urban facilities. This study analyzes cab drivers' stay behaviors using a taxi GPS trajectory dataset collected in Wuhan, China. By extracting cab drivers' stay activities from the dataset, we measure the activity frequency at the level of traffic analysis zon...

Public transport system plays an important role in developing sustainable cities. The increasingly available transport big data such as the smart card data (SCD) provides new opportunities to shape deep light into this type of knowledge with unprecedented resolutions. However, most existing studies either only analyse the static structure of Public...

Weather radar data plays an important role in meteorological analysis and forecasting. In particular, the web-based real-time 3D visualization will enable and enhance various meteorological applications by avoiding the dissemination of large amount of data over the Internet. Despite that, most existing studies are either limited to 2D or small-scal...