Standardized Green View Index and Quantification of Different Metrics of Urban Green Vegetation

Yusuke Kumakoshi,Xiaojiang Li,Yuji Yoshimura,Sau Yee Chan,Hideki Koizumi

doi:10.3390/su12187434

Yusuke Kumakoshi, Xiaojiang Li + Show 3 more

Open Access

https://doi.org/10.3390/su12187434

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Journal: Sustainability	Publication Date: Sep 10, 2020
Citations: 35	License type: CC BY 4.0

Affiliation: The University of Tokyo, Temple University

Abstract

Urban greenery is considered an important factor in sustainable development and people’s quality of life in the city. To account for urban green vegetation, Green View Index (GVI), which captures the visibility of greenery at street level, has been used. However, as GVI is point-based estimation, when aggregated at an area-level by mean or median, it is sensitive to the location of sampled sites, overweighing the values of densely located sites. To make estimation at area-level more robust, this study aims to (1) propose an improved indicator of greenery visibility (standardized GVI; sGVI), and (2) quantify the relation between sGVI and other green metrics. Experiment on an hypothetical setting confirmed that bias from site location can be mitigated by sGVI. Furthermore, comparing sGVI and Normalized Difference Vegetation Index (NDVI) at the city block level in Yokohama city, Japan, we found that sGVI captures the presence of vegetation better in the city center, whereas NDVI is better at capturing vegetation in parks and forests, principally due to the different viewpoints (eye-level perception and top-down eyesight). These tools provide a foundation for accessing the effect of vegetation in urban landscapes in a more robust matter, enabling comparison on any arbitrary geographical scale.

Highlights

According to the United Nations [1], the proportion of the world population living in cities is expected to increase from 55% in 2018 to 68% by 2050
This study aims to establish a method for such area-based study that mitigates bias from spatial distribution of Green View Index (GVI) sites
This study proposed standardized GVI, which is able to consider the heterogeneous relation among sites

Summary

Introduction

According to the United Nations [1], the proportion of the world population living in cities is expected to increase from 55% in 2018 to 68% by 2050. As the city becomes more densely populated, sustainable development is more indispensable than ever, in order to tackle problems such as mitigation of climate change and enhancement of the quality of life of citizens in the city Amid these challenges, urban green space is expected to provide positive effects on different aspects in the city, such as reduction of air and water pollution [2,3,4], mitigation of urban heat effect [5,6], and various aspects of public health [7,8,9,10,11]. Accessibility to green space registered in land use data is often employed as a representation of urban greenery This approach does not fully capture people’s exposure to green vegetation in that some types of vegetation are tend to be ignored such as street trees. NDVI does not represent people’s perception of green vegetation due to its top-down viewpoint; studies have shown that people on the street often see vegetation in horizontal direction or canopy in an elevated direction [17,18]

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