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Song X.,Nanjing University | Pu Y.,Nanjing University | Pu Y.,Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology | Liu D.,Nanjing University | Feng Y.,Nanjing University
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica

Urban functional area is an important concept in urban planning. It is difficult to obtain regional functional properties by remote sensing techniques since land uses are not always directly observable even by the closest inspection. With the development of Internet and popularity of mobile positioning devices, a large volume of pedestrians' movement trajectories are available to the common. This paper applies machine learning method to discover urban functional areas implicit in the GPS data. The analytic framework is built on an idea that people's movement patterns and trip rules have a strong correlation with regions' functions. Gaussian Mixture Model (GMM) is applied to extract different functional clusters through iterative machine learning process. About 60 areas are therefore sampled to determine the specific functional areas for residential, commercial, governmental, educational and leisure area. The 6 functional areas are identified with the help of samples' temporal distributions. The preliminary results indicate that urban functional areas can be discriminated by integrating GPS movement trajectories with machine learning method, especially with large amount of data. This spatial data mining process is simple, applicable and easy to be carried out in the actual production. © 2015, SinoMaps Press. All right reserved. Source

Shen D.,Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology | Shen D.,Nanjing University | Shen D.,Changjiang River Scientific Research Institute | Wang J.,Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology | And 4 more authors.
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica

The conventional flood inundation methods based on DEM data usually have some disadvantages. For example, the seed filling method which is a popular flood inundation method can not get better result when the data amount is huge, and also it reflects low computational efficiency due to too many recursive operations. To resolve this problem, this paper proposes a quick flood inundation algorithm based on massive DEM data. It focuses on strip-divide method and real time raster compression storage technology. The paper makes the comparison between the common seed filling algorithm and strip-divide seed filling algorithm, the results show that this algorithm greatly improves the computational efficiency. At the same time, it resolves the problem of massive DEM data analysis. Source

Li F.,Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology | Peijun D.,Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology
Joint Urban Remote Sensing Event 2013, JURSE 2013

Over the past 30 years, urban development in China has been remarkable. Land development and consumption have been out of control and have kept expanding out of order, especially to marginal areas of some metropolises. Therefore, dynamic change monitoring of urban sprawl is necessary. Taking Jiangning District, Nanjing City as a research area, this paper demonstrates the dynamic change of urban sprawl by Landsat MSS/TM data. Furthermore, three-dimensional indicators are considered based on the actual situation of urban sprawl in Jiangning in order to better reflect the nature of sprawl. The result indicates that the trend of urban sprawl is significant. From 1979 to 1988, the phenomenon of disorder and scattered construction was obvious in Jiangning; from 1988 to 1997, sprawl is more significant in the process of suburbanization. Leapfrog development is significant; from 1997 to 2003, the land became fragmented, resulting in a broken landscape. © 2013 IEEE. Source

Pu Y.,Nanjing University | Pu Y.,Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology | Pu Y.,Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application | Han H.,Shandong University | And 3 more authors.
Dili Xuebao/Acta Geographica Sinica

Population migration flows between different regions are related to not only the origin- and destination- specific characteristics, but also to the migration flows to and from neighborhoods. Intuitively, changes in the characteristics of a single region will impact both inflows and outflows to and from other regions. In order to explore the spatial interaction mechanism driving the increasing population migration in China, this paper builds the spatial OD model of interprovincial migration flows based on the sixth national population census data and related social- economic data. The findings are as follows: (1) Migration flows show significant autocorrelation effects among origin and destination regions, which means that the migration behavior of migrants in some region is influenced by that of migrants in other places. The positive effects indicate the outflows from an origin or the inflows to a destination tend to cluster in a similar way. Simultaneously, the negative effects suggest the flows from the neighborhood of an origin to the neighborhood of a destination tend to disperse in a dissimilar way. (2) Multilateral effects of the regional economic and social factors through the spatial network system lead to the clustering migration flows across interrelated regions. Distance decay effect plays the most influential force in shaping the patterns of migration flows among all the factors and the negative spillover effect further aggravates the friction of distance. As for destinations, the influence of wage level and migration stocks is beyond that of GDP and the positive spillover effects of these factors enhance the attraction of neighborhood regions. The spillover effects of unemployment rate and college enrollment of higher education are significantly negative while the effect of population in a destination is not significant. As for origins, population and migration stocks lead to positive spillover effects on the neighborhoods while the effects of other factors are negative. (3) Changes in the regional characteristics will potentially lead to a series of events to the whole migration system, and the flows to and from the center of oscillation and its neighborhoods vibrate greatly compared with other regions. The simulation results of 5% GDP increase in Jiangsu province indicate that the outflows to other regions decrease while the inflows from all others increase to some different extent. Comparatively, the influence on the flows to and from the regions neighboring Jiangsu is significant while that of remote regions is much less, which cannot be explained by the traditional gravity model. © 2016, Science Press. All right reserved. Source

Shen D.,Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology | Shen D.,Nanjing University | Shen D.,Changjiang River Scientific Research Institute | Shen D.,Chinese Ministry of Water Resources | And 9 more authors.
Hydrology and Earth System Sciences

The rapid progress of lidar technology has made the acquirement and application of high-resolution digital elevation model (DEM) data increasingly popular, especially in regards to the study of floodplain flow. However, high-resolution DEM data pose several disadvantages for floodplain modeling studies; e.g., the data sets contain many redundant interpolation points, large numbers of calculations are required to work with data, and the data do not match the size of the computational mesh. Two-dimensional (2-D) hydraulic modeling, which is a popular method for analyzing floodplain flow, offers highly precise elevation parameterization for computational mesh while ignoring much of the micro-topographic information of the DEM data itself. We offer a flood simulation method that integrates 2-D hydraulic model results and high-resolution DEM data, thus enabling the calculation of flood water levels in DEM grid cells through local inverse distance-weighted interpolation. To get rid of the false inundation areas during interpolation, it employs the run-length encoding method to mark the inundated DEM grid cells and determine the real inundation areas through the run-length boundary tracing technique, which solves the complicated problem of connectivity between DEM grid cells. We constructed a 2-D hydraulic model for the Gongshuangcha detention basin, which is a flood storage area of Dongting Lake in China, by using our integrated method to simulate the floodplain flow. The results demonstrate that this method can solve DEM associated problems efficiently and simulate flooding processes with greater accuracy than simulations only with DEM. © Author(s) 2015. Source

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