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The city region has emerged as an important form of regional development and governance. However, the dynamics of spatial inequality in city regions are misunderstood. This study examines the Yangtze River Delta (YRD) to determine the spatiotemporal evolution of regional inequality across prefecture-level municipalities from 1990 to 2018. It finds that regional inequality has steadily increased since the 1990s but has declined somewhat in recent years. This is associated with faster growth and higher upward mobility of central regions in the early reform period and increases in the upward mobility of the periphery in recent years. The gradient-distance curve of the Shanghai-centered economy sharpened and then flattened, indicating the polarization of growth in the core regions, followed by the diffusion of development and improved regional integration. However, the core-periphery remains stronger within provinces between provincial capitals and other regions. Despite regional integration and peripheral development, the problem of spatial exclusion and core-periphery structures persists. More attention needs to be given to the core-periphery relationship and the development of peripheral regions to promote regional integration and reduce spatial polarization. [ABSTRACT FROM AUTHOR]

For large-scale 3D building reconstruction, there have been several approaches to utilizing multi-view satellite imagery to produce a digital surface model (DSM) for height information and extracting building footprints for contour information. However, limited by satellite resolutions and viewing angles, the corresponding DSM and building footprints are sometimes of a low accuracy, thus generating low-accuracy building models. Though some recent studies have added GIS data to refine the contour of the building footprints, the registration errors between the GIS data and satellite images are not considered. Since OpenStreetMap (OSM) provides a high level of precision and complete building polygons in most cities worldwide, this paper proposes an automatic single building reconstruction method that utilizes a DSM from high-resolution satellite stereos, as well as building footprints from OSM. The core algorithm accurately registers the building polygons from OSM with the rasterized height information from the DSM. To achieve this goal, this paper proposes a two-step "coarse-to-fine registration" algorithm, with both steps being formulated into the optimization of energy functions. The coarse registration is optimized by separately moving the OSM polygons at fixed steps with the constraints of a boundary gradient, an interior elevation mean, and variance. Given the initial solution of the coarse registration, the fine registration is optimized by a genetic algorithm to compute the accurate translations and rotations between the DSM and OSM. Experiments performed in the Beijing/Shanghai region show that the proposed method can significantly improve the IoU (intersection over union) of the registration results by 69.8%/26.2%, the precision by 41.0%/15.5%, the recall by 41.0%/16.0%, and the F1-score by 42.7%/15.8%. For the registration, the method can reduce the translation errors by 4.656 m/2.815 m, as well as the rotation errors by 0.538°/0.228°, which indicates its great potential in smart 3D applications. [ABSTRACT FROM AUTHOR]