基于网格的街区尺度城市绿度度量方法

本文提出一种基于网格的街区尺度城市绿度度量方法。其以900 m×900 m的网格单元作为以城市主干道划分所形成街区尺度的表征,根据网格单元内植被覆盖度与植被构成之间的关系构建绿度指标。通过与传统的基于植被面积占比的格网法所计算的绿度指数进行比较。发现本文方法建立的绿度指标能在街区尺度上提供更加丰富的城市绿度信息,有效地解决了传统方法难以反映的植被覆盖度近似区域因其内部植被构成不同所带来的绿度差异问题。为城市规划、设计以及管理提供了一种新视角。基于该绿度指标,利用Landsat TM/OLI 2009、2015和2019年不同季节的遥感数据分析北京市城市绿化的时空变化特征。结果表明：北京市主城区城市绿化的面积和质量在2009—2019年显著提升,且秋季最为明显。绿化的变化在四环内外呈现出不同的模式。四环内主要为绿化面积的增加,四环外则在绿化面积和绿化质量上都有明显的增长。

A Measure of Block Scale Urban Green Index in Urban Area based on Grid Method

To quantify urban green space using remote sensing data, this paper proposed a grid-based urban green space measurement method at city block scale. The grid unit of 900 m×900 m was set to represent the block scale formed by the main road of the city. The vegetation coverage and vegetation composition were used together to generate the green index in each unit. Unlike the green index calculated by the traditional grid method based on the proportion of vegetation area, the green index in this paper enhanced urban greenness information particularly in areas with moderate to high vegetation coverage. We applied this method in Beijing city and diagnosed the spatiotemporal differences of local urban green space over years. We used Landsat TM/OLI datasets of 2009, 2015, and 2019 in spring, summer, and autumn, respectively. Results showed that both the quantity and quality of urban green space in Beijing have increased significantly from 2009 to 2019, especially in autumn. The changes of urban green space showed different patterns inside and outside of the Fourth Ring Road. Vegetation coverage showed an increase within the Fourth Ring Road, while outside the Fourth Ring Road, there was a significant increase in both vegetation coverage and quality.