Mapping megacity growth with multi-sensor data

In our increasingly urbanized world, monitoring and mapping of urban growth and thereby induced land-use and land-cover change (LULCC) is of emergent importance. Remote sensing can reveal spatio-temporal growth trajectories of cities, which again allow a thorough understanding of the impacts of urbanization on ecosystems and ecosystem services. However, the mapping of urban areas remains one of the most challenging tasks of remote sensing data analysis. This paper presents an approach to map urban growth from multi-sensoral data, exemplified for the Dhaka megacity region in Bangladesh between 1990 and 2006. The approach is globally applicable and can facilitate regional urban growth maps in arbitrary complex and dynamic environments.Dhaka's densified urban landscape, its deltaic locality and the highly dynamic monsoon-related phenology call for a sophisticated analysis approach that is able to separate intra-annual land-cover variations from actual urbanization. Imagery from the Landsat series of satellites is a great asset for such an analysis due to its synoptic coverage of large urban areas as well as its unique historical archives. In our approach, we solve problems of spectral ambiguities and seasonal phenological dynamics through incorporating multi-temporal imagery for each monitoring year (1990, 2000, and 2006) and by extending the spectral feature space with synthetic aperture radar (SAR) data. The resulting datasets are heterogeneous and comprise measurements of unequal scaling. Non-parametric classification algorithms are required to delineate multi-modal and non-Gaussian class distributions of heterogeneous as well as temporally and spectrally complex land-cover classes of interest in such an extended feature space. We therefore used a support vector machine (SVM) classifier and post classification comparison to reveal spatio-temporal patterns of urban land-use and land-cover changes. An SVM based forward feature selection procedure allowed deriving in-depth information about the individual contribution of different input bands.Our methodology delineated relevant land-cover classes and resulted in overall accuracies better than 83% for all years considered. Change analysis unveiled a profound expansion of urban areas at the expense of prime agricultural areas and wetlands. During the 1990s, change was primarily characterized by a densification of urban fabric, whereas more recent changes included vast in-filling of low lying land and an extensive industrial sprawl into Dhaka's peri-urban areas. Our multi-sensoral and multi-temporal mapping approach allowed for delineating temporally dynamic LULCC, which again allowed for an insightful characterization of land system changes in the megacity region of Dhaka.     

探索国内外五个特大城市新城发展共性,引导上海新城建设

通过对伦敦、巴黎、香港、东京和首尔等国内外特大城市新城发展的案例分析,总结和探索了这些取得成功的新城在技术层面(包括规模、距离、交通等方面)和在政策层面的共性。在此基础上,对新时期上海的新城建设做出了相应的评价,并给出了规划和政策建议。     

Urban growth: Changes,management, and problems in large cities of Southeast China

Compared with medium-sized cities, megacities play an increasingly important role in the rapid urbanization process in China. Owing to the expanding scale of large cities, urban sprawl leads to unsustainable practices that cause ecological, social, and environmental problems. Urban planning and land use planning are major driving forces of land use and land cover change in China. However, the goals of these two types of planning are different, and coordinating them is a challenge for local government decision makers. Thus, we use the SLEUTH model to simulate the implementation scenarios of future urban growth in Nanjing in the Jiangsu province of China. Using the scientific simulation data of the model, we contrasted the alternative futures of the two planning types for local government decision makers to achieve sustainable urban planning.The objective of our study is to explore the problems and possible solutions for urban management in the context of amegacity in China. The results of our study confirm the value of SLEUTH, which provid esextensive exploratory knowledge in evaluating the effects of possible local government decisions.     

特大城市公共卫生风险识别及规划应对

特大城市具有人口高度密集、资源要素高度集聚、国际交往频繁、辐射能力和影响力大等显著特征。随着全球化程度不断加深,特大城市受突发公共卫生事件影响的概率将会显著增加。文章以广州市为例,聚焦特大城市人口特征、公共卫生防疫体系、传染病救治和城市治理等方面,分析、识别公共卫生安全风险点,并重点从城乡规划角度提出建立区域联防联控机制、加强高危空间识别与管控、保障传染病救治空间、开展卫生防疫专项规划编制、提升社区治理能力等对策和建议。     

区域设计 在中国国土空间规划中的定位:长江三角洲巨型城市区的项目探索

By restructuring its planning system and integrating competences of land resource and water management, environmental conservation, agriculture, as well as spatial planning, under a same Ministry of Natural Resources in 2018, China ambitioned to definitively turn the page on inconsistent and sectoral planning practices. However, existing planning instruments are still linked to administrative boundaries and remain statutory and regulatory in nature, which makes them inadequate to address complex and dynamic megacity regions that span across different administrative entities. The Yangtze River Delta megacity region is the subject of an ambitious integration plan which focuses on economic coordination and urban services, however, there is still no coherent vision on its spatial development at the territorial scale. This article presents the “Jiangnan Park,” a university-led and design-driven research project focusing on the vast triangular plain between cities of Shanghai, Hangzhou, and Suzhou. Using the encompassing metaphor of regional “park” and applying the emerging method of regional design, this project combines mapping, visualization, design strategies, and workshop techniques to elaborate a development vision for this historically and ecologically sensitive area. As a pioneering case of regional design in China, this project exemplifies how the use of cross-scale and cross-sectoral collaborative methods can inform the development of integrative strategies for complex megacity regions.     

超大城市地表特征参数估算及其对城市热环境的影响研究

近年来超大城市的下垫面环境发生了显著变化,并对区域生态系统造成了明显的影响。因此有必要定量化下垫面特征参数并研究它们之间的相互关系对城市热环境的影响。以北京市为例,采用2009年6月2日Landsat\|5 TM卫星影像提取城市不透水层百分比、地表温度、土地利用/土地覆盖和植被指数这些典型地表特征参数,并分析它们之间的定量关系。研究结果表明:随着城市化进程加快,北京市高不透水面扩展到六环,六环以内地表温度保持在40 ℃以上,特别是商业区等特高不透水面区域地表温度甚至高达45 ℃,处于城市高温区域,六环以内区域平均温度波动幅度不大。另外,森林和农业用地的降温作用明显,最高降温幅度达到6 ℃,而且夏季裸土地表温度接近高密度居民区地表温度。     

Hello Stranger: Phenomenology and Topography of the Megacity

Caroline Bos of UNStudio counters the city theme of this issue of Architectural Design with the spectre of the megacity. The very recent emergence and scale of the Asian megacity, she argues, requires a very different architectural treatment to the European or North American metropolis. It is one that should be understood through an experiential approach that brings to the fore spatial and visual relations between people, and people and things, asking, for instance, how so many strangers can be so visibly at home in public urban space.