Sensing Public Space

We aim to sense/monitor public space using emerging data and cutting-edge technologies using images from CCTV or (hunting) cameras we set by ourselves, Wi-Fi probes, wearable cameras and deep learning algorithms. We aim to digitalize Jan Gehl's theory in this project.


侯静轩 2022 博士论文_公共开敞空间.pdf
Adobe Acrobat Document 28.1 MB

Measuring pedestrian flows in public spaces: Inferring walking for transport and recreation using Wi-Fi probes

Differentiating transport and recreational walking in public spaces could promote the precise design of walkable public spaces for different walking demands to encourage more walking behaviors. However, previous studies  mainly relied on field observations and self-reports, failing to quantitatively distinguish and depict the spatiallevel usage of transport and recreational walking of all pedestrians passing by. This study proposed an approach based on the traffic counts and the number of pedestrians to infer transport and recreation walking in public spaces. A comparative experiment using Wi-Fi probes to collect pedestrian data in a gated residential community and a creative center in Beijing, China, was conducted to verify the applicability of this method. The results demonstrated that the transport walking index (the number of pedestrians) could portray the volume of transport walking, and the recreational walking index (average traffic counts of each pedestrian) could depict the proportion of recreational walking in public spaces. Two tests using different time threshold parameters and field observations verified the robustness of the results. Given the low-cost and long-duration observation, this method can potentially support the process of Post Occupancy Evaluation and Environment and Behavior research in more public spaces to make them more walkable.
Hou et al 2023_BAE_WiFi.pdf
Adobe Acrobat Document 16.7 MB

Small public space vitality analysis and evaluation based on human trajectory modeling using video data

Small public spaces are important for citizens to live and socialize with a high utilization rate. The vitality of  small public space plays an important role in evaluating space quality and attraction and provides reference for urban governance issues such as vitality evaluation of public space, quality optimization, and site micro-renewal. Previous studies of vitality based on low-throughput surveys or big data with low positioning accuracy are not suitable for the high-efficiency study of small public space. In this study, a systematic framework of vitality quantification in small public spaces is built on fine-grained human trajectories extracted from videos for more efficient and refined human-oriented vitality evaluation. A multi-indicator vitality quantification method is first proposed to comprehensively represent human vitality, including number of people, duration of stay, motion speed, trajectory diversity and trajectory complexity. Furthermore, a video dataset of small public space along with our sub-index-assisted expert assessing scheme is proposed to evaluate our vitality quantification framework. Finally, we analyze the correlation between quantitative vitality indicators and the expert-assessing vitality through multiple linear regression and obtain the optimal vitality quantification model. The experimental results indicate that our dataset is reliable and the vitality quantification model constructed with our quantitative indicators can better characterize urban vitality than the previous model based on number of people and staying time.
Niu et al 2022 BAE_UrbanVitalityVideo.pd
Adobe Acrobat Document 7.3 MB

Quantifying the usage of small public spaces using deep convolutional neural network

Small public spaces are the key built environment elements that provide venues for various of activities. However, existing measurements or approaches could not efficiently and effec- tively quantify how small public spaces are being used. In this paper, we utilized a deep con- volutional neural network to quantify the usage of small public spaces through recorded videos as a reliable and robust method to bridge the literature gap. To start with, we deployed photographic devices to record videos that cover the minimum enclosing square of a small public space for a certain period of time, then utilized a deep convolutional neural network to detect people in these videos and converted their location from image-based position to real-world projected coordinates. To validate the accuracy and robustness of the method, we experimented our approach in a residential community in Beijing, and our results confirmed that the usage of small public spaces could be measured and quantified effectively and efficiently.

Hou et al 2020 PlosOne_SmallPublicSpaces
Adobe Acrobat Document 2.0 MB

Public Space Vitality Representation Based on Space Trajectory Entropy

People and their activities are the core of the vitality of urban public space. The measurement of public space vitality focusing on people and their activities has always been a difficulty in human-scale urban researches. In view of the representation of public space vitality, this research proposes a new method of spatial vitality representation based on the crowd trajectory clustering. In this method, the multi-object tracking technology based on videos is used to extract the trajectory of the crowd, which is further clustered based on the trajectory structure. According to the diversity of trajectory categories and the difference of structures, “the space trajectory entropy” is put forward to reflect the diversity and mixing degree of the behavior patterns in public space, and to measure the complex state of crowd activity from a novel and concise perspective, so as to represent the vitality of public space. In this research, three public spaces in Wuhou District of Chengdu City are selected as the research objects. The spatial trajectory entropy of the three scenes is calculated under this method. Combined with manual review, it explores the changes and causes of the time series of spatial vitality of the three scenes and gives spatial optimization suggestions. The results show that the spatial vitality characterization method can objectively describe the temporal and spatial movement of the crowd, precisely reflect the spatial-temporal vitality of space, reflect the exact urban operation and maintenance reality in the space, and contribute to establish a human-scale dynamic evaluation mechanism of spatial vitality. As a result, the proposed work can provide precise technical support for city governance, such as public space vitality assessment, quality optimization and site micro-renewal.

Our paper published in Chinese
刘博等 2022 风景园林_公共空间活力.pdf
Adobe Acrobat Document 5.9 MB

Other works ongoing in this direction 敬请期待