Jingsong Ma

GIS-based method of delimitating trade area for retail chains

Delimitating trade area with accuracy is a major concern for retail and service companies who want to adapt their marketing strategy to be competitive in todays highly competitive chain industry. A collection of methods have been proposed to delimitating trade area, but either some are too simple or the necessary data are not available. In this article, a geographic information system-based method for precisely delimitating trade area is proposed. It is based on the fact that the social and economic activities are actualized along the street networks. The trade area can be delineated in terms of time distance with high precision taking the practical traffic situations into account. In addition, centered on this method of delimitating trade area, a wide array of functions can be extended to support both operational day-to-day and long-term strategic decision making for retailers.

A real-time parallel implementation of Douglas-Peucker polyline simplification algorithm on shared memory multi-core processor computers

GIS software requires the ability to simplify polyline features in real-time when displaying linear vector data with plenty of vertices. The Douglas-Peucker polyline simplification algorithm has been widely adopted in this area for decades, though it is often criticized for its low performance when exist a large number of vertices on a polyline which should be subdivided into many separate segments and calculated perpendicular offsets repeatedly in the algorithm. That was the main obstacle to accomplish real-time simplification and displaying. As shared memory multi-core processor computers become more widely available, it might be a good opportunity to improve the performance of the Douglas-Peucker method by converting its sequential implementation to parallel form. This paper presents two different parallel implementations. The first is done by separating a polyline feature into irrelevant segments and distributing segments to parallel threads. The second dispatches each polyline feature to an idle parallel thread in which the conventional sequential method is applied. By utilizing the official Chinas provincial boundary geospatial data set, and C++ language for programming, performances on various shared memory multi-core processor computers (including dual-core, triple-core, and quad-core processors from AMD and Intel respectively) are compared among the four implementations together with the original sequential forms. It is proved that with the increment of processors cores and the number of threads accordingly, the parallel algorithms will efficiently reduce the number of vertices of a polyline and generate multi-resolution polyline data, which will dramatically speed up the process of simplifications and thus real-time display effects are achieved.

Spatial-temporal dynamics of Sichuan industrial structure with Markov chains approach

The status of things always changes with the process of time. Markov chains approach considers that as long as the current status is known, the future state of things can be forecasted without understanding the past state. Considering the spatial autocorrelation of spatial things, Markov chains is combined with spatial autocorrelation to develop the spatial Markov chains to study the influence of regional background on regional transition. The industrial structure of regions alters in different periods of time, and its development process and tendency can be approached approximately by using Markov chains methods. Based on the coefficient dataset of industrial structure at the county level in Sichuan province from 2000 to 2007, this paper attempts to apply Markov chains and Spatial Markov chain to investigate the spatial and temporal characteristics of industrial structure level in Sichuan. Firstly, all the coefficient data of industrial structure in Sichuan are classified into 4 different classes (low, middle-low, middle-high and high) and Markov transition probability matrix is estimated to explore whether the convergence of industrial structure level exists in Sichuan. Secondly, conditioning on each regions spatial lag at the beginning of each year, spatial Markov matrices are constructed to investigate the relationship between transition probability of different regions and their neighbors, and maps are accordingly made in order to visualize spatial patterns of class transitions. Thirdly, the evolutionary trends of industrial structure level in the next twenty years, fifty years and one hundred years are forecasted respectively by computing the twentieth, fiftieth and hundredth power of Markov transition probability matrix. Finally, the measures to improve the industrial structure level in Sichuan province are given.

An integrated approach of Multi-Criteria Suitability Evaluation and Cellular Automata modeling for urban growth simulation

In this paper, based on the ArcGIS 9.3 platform and python scripts, an approach of integrated CA and Multi-Criteria Suitability Evaluation (MCSE) analysis is developed to simulate the changing land use patterns of urban area in the past decades. The methods are designed to allow slow edge growth around towns and villages, rapid edge growth around cities and permits random growth only within the suitable development area. Take the City of Waterloo as a study area, and base on the understanding of the logistic trend and spatial pattern of urban and region development processes. By implementing the model in raster analysis environment of ArcGIS, this study extracts more precise influencing factors of urban growth, and then uses Multi-Criteria suitability evaluation analysis methods to create a satisfying suitability raster dataset. After the improved accuracy tests with CA automation, especially in the random growth model, the desirable results show the dynamic development of urban areas of Waterloo region between the 1960s and 1990s. Several experimental scenarios of development of Waterloo region under realistic conditions are also presented using animation technology in ArcScene. This study shows that experimental application in the study area which produced realistic results and demonstrated the model was theoretically valid and feasible. In the last part, the analytical thinking on urban stimulation using CA and GIS are also discussed.

Decomposition method of raster geographic data based on parallel computing

The paper mainly studied decomposition method of raster geographic data based on parallel computing. Firstly, we structured computational transformation model of raster geographic data; Then, we designed a computational experiment to validate the computational transformation model and evaluate the performance of k-NN classification algorithm. Results of parallel computational experiment show that the model can be applied to decompose a heterogeneous spatial computational domain representation into a balanced set of computing tasks; the speedup performance of parallelizing k-NN classification algorithm based on the transformation model is superior to the results from traditional method.

A new trapezoidal-mesh based data model for spatial operations

This paper presents a new spatial data model based on trapezoidal-mesh for implementing spatial operations within geographical information systems (GIS). Based only on the solid foundation of spatial operations, diversified application models can be established to bridge the gap between Digital Earth models and the real world with its real-world problems (‘connecting through location’). In this paper, the involved polygon features are decomposed into a series of trapezoidal-meshes. Then, geo-processing operations are employed on these meshes rather than the original polygon features, resulting in a relatively simple spatial computation. As a kind of model designed by integrating raster with vector, the model presented here has advantages over other models when carrying out spatial operations insofar as providing a solid foundation for achieving the grand goal of Digital Earth. The concept of this data model and the two extensive examples of its application in spatial operations are elaborated upon in this article. As a result, this article and the research that supports it, proves that the adoption of the trapezoidal-mesh model greatly improves the efficiency of spatial operations in GIS.

A novel cartography scheme based on run-length operation

Map exporting plays a crucial role in the realization of spatial data visualization. However, this process will be slow and high memory required when dealing with high precision map or enormous data. A fast cartography approach based on run length coding is proposed in this paper. The main idea is to express map symbol using run length set rather than dot matrix, thus the disposal of various form of symbol, linetype or label in cartography pattern can achieve through the operation of run length set, which will largely cut down redundant information emerged in the process of map rendering. The core of our scheme is geographical element expression with run-length set and run length overlay calculation of multiple layers, specifically to explore how map symbol and cartographic products are created by using run-length code. A detailed description about design of dot-form symbol is presented in this paper. We argue that dot-form symbol is a block of different size run-length segment, which records the complete color attribute. The design of complex symbol is built through the operation of fundamental run-length block, which have been implemented in previous research. In addition, other styles of map symbol can create in the same pattern. Based on this representation, it is actually plug in a block of run-length when insert a symbol into map layer. Thus, the map document can be taken as a set of run-length in different layers. While the map product is the final superposition effect of layers, combination of run-length block in each layer is necessary for the ultimate cartography pattern. The procedure is as follows: (1) progressive scan cartography space; (2) compare each layer with uppermost layer to determine merge or resolve run-length blocks to form ultimate run-length set, which is executed by adding operation of run-length for layers. The rules of disposing run-length block or not is discussed in detail. Thereby, all cartography features are contained in the final run-length set and map export will be realized in a short time for smaller memory space. The advantages of the scheme in speed and memory consumption are illustrated by comparative analysis with existing cartography system. Simultaneously, performance analysis concerning thematic map series is made at the end of this paper.

Research on urban accessibility distribution areal model by Floyd algorithm and Kriging interpolation

As an important indicator to measure a citys regional economic and social value, accessibility is more and more used in tourism and urban planning, transport design, public facilities and some other issues. Traditional accessibility study is mostly focus on a limited number of points. In this paper, GIS technology is used to establish an innovative areal model of the whole citys accessibility, in order to carry out a more comprehensive analysis of geographical accessibility. Taking Nanjing as a case study, we established the topological road network. The Floyd algorithm was used to carry out the shortest paths between all the nodes. In order to obtain an areal model of the whole citys accessibility factor, we applied Kriging interpolation compensate for the lack of data, and then used ArcGIS to establish the areal model of Nanjing. Our model matches the actual situation perfectly, proving the effectiveness of the method.

Reasearch on the spatial autocorrelation of economic growth in Shandong Province based on county scale

This paper, with the help of global and local spatial autocorrelation methods, analyzed the spatial differences among the level of regional economic development and the economic growth rate in Shandong Province with data of county GDP per capita and GDP per capita growth rate from 1995 to 2007. The results showed that: (1) in the study period, the spatial difference among the county-level economy in Shandong Province overall became narrow. (2)The spatial disparities among county-level economy in Shandong Province have decreased continuously. Even the centre region of Shandong Province, which the spatial differences were quite large, begins to develop rapidly with the development of the neighbor areas. (3) In the study period, the average growth rate of county-level economy in Shandong Province demonstrated aggregated distribution. High-high and low-low areas obviously represent spatial differential, the high-high cluster in Shandong Peninsula while low-low cluster in westsouth of Shandong. The growth rate of high-developed Shandong peninsula is high-high aggregated, while the growth rate of the less-developed southwest region is low-low aggregated. It indicates that the unbalance of regional economy development in Shandong province will further aggravate.

The construction of spatial weight matrix based on discrete points through building a searching area for each point

In this paper, we present an algorithm to construct a spatial weight matrix by employing the threshold method to measure the spatial connectivity among discrete spatial points. This method can save searching costs by building a searching area for each point when we set values for each element of the weight matrix, and achieve optimization in the process of constructing a spatial weight matrix. The algorithm presented here has been implemented with Python programming language. A sample of 6122 discrete points of the aerosol optical thickness is used to test the efficiency of the algorithm through figuring out the datasets spatial autocorrelation indices.