基于四叉树索引和双缓存机制的GIS动态可视化模型设计与实现

针对GIS数据的多维、海量、动态性等特点,本文设计了基于四叉树和双缓存机制的GIS动态数据可视化模型,并详细地介绍并阐述该模型的数据存储规格和数据可视化方法及其特点。基于四叉树索引结构和多线程双缓存机制,构建GIS动态数据可视化模型,探讨多线程分层绘制动态对象方法和GIS空间数据库实时更新方法,实现GIS海量数据的动态化、序列化、实时可视化表达。并测试对比了常见可视化算法与本算法之间的显示效率,发现本研究算法针对多种GIS图形类型、大数据量GIS数据显示,均有较高的效率提升,实验证明该方法稳定可行,可为其他GIS动态数据的可视化提供参考。

新一代GIS基础软件的四大关键技术

近年来,信息技术在地理信息技术的发展过程中发挥着越来越重要的作用。伴随着云计算与大数据在地理信息领域的应用,地理信息技术步入了一个新的发展阶段。本文从我国地理信息技术的发展历程出发,总结了当今GIS技术的发展情况。包括:将地理信息运行环境从Windows操作系统扩展到Linux和UNIX操作系统的跨平台GIS技术,推动GIS应用从桌面PC端延伸到云端、Web端和移动端并实现云端互联与云端协同的云GIS技术,涵盖从二维空间到全空间地理信息且具备对象级三维空间分析能力的三维GIS技术,以及支撑大规模多源异构数据的价值挖掘和知识发现的大数据GIS技术。

通用三维GIS场数据模型研究与实践

随着三维地理信息系统(geographic information system,GIS)应用的发展,空中电磁信号场、空气与水体污染场、地下地质属性场等连续、非匀质的三维空间属性场数据进行建模、可视化与分析计算对GIS基础软件提出了新的挑战。已被广泛应用的TIN(triangulated irregular network)与栅格数据属于表面模型,通常用来表达二维场数据,其中由TIN组成的封闭表面可用于表达三维体,但两者都无法描述非匀质、连续变化的三维属性场。探讨了在通用GIS基础软件中基于TIN和Grid进行升维表达,实现不规则四面体网格(tetrahedralized irregular mesh,TIM)和体元栅格(voxel grid)两大类三维空间场数据模型,分析了两类数据模型的特点,探讨了三维场数据在可视化和分析计算方面的关键技术,实现了基于TIM与体元栅格表达和应用三维GIS场数据,完善了GIS三维数据模型体系,实现了空/天、地表、地下全空间的一体化表达、模拟与分析计算。

A local spatial decision support system for developing countries based on MCA,fuzzy sets and OWA–case study of a municipality in Cuba

This paper presents a Spatial Decision Support System for local governments of developing countries.It allows municipality government,enterprises,scientific community and civil society to address decision problems using GIS.The framework is supported by four modules of information technologies:Environmental Decision Support Database,Data Manipulation,Decision Support,and Mapping.A case study is presented covering the implementation of this framework in one municipality of Cuba.An example of land suitability planning for coconut crops is used to evaluate the system performance and usability.Results show local municipalities are able to use this framework to solve local decision problems using state of the art decision making even with low infrastructure development.

A new synchronization in parallel shortest paths analysis for massive road networks

To effectively solve the single-source shortest path(SSSP)problem for massive road networks in geographical information systems,a new synchronization method is proposed in the implementations of parallel SSSP algorithm.It applies spinlock by inline assembly language for the sake of small overheads of controlling the interaction of multiple threads.The performance of our method is compared with widely used Pthreads application programming interfaces and the powerful sequential solution given by DIMACS.The experimental platform is a shared address space workstation with two processors(i.e.eight cores)at a clock speed of 3 GHz.Problem instances for experiments contain a directed road networks of the USA with more than 23 million vertices and 57 million edges,and its 11 subnetworks of variant sizes.This method answers the SSSP of the USA road network in 1231 ms,while Pthreads costs 1808 ms and DIMACS sequential solution takes 4856 ms.It achieves a speedup of 3.95,which is 47%faster than Pthreads with the speedup of 2.69.When the size of instance is larger,our method achieves a better performance.

Competitive Learning Approach to GIS Based Land Use Suitability Analysis

This paper uses the expected utility under risk hypothesis to develop a new approach to GIS modeling for land use suitability analysis with competitive learning algorithms （CLG-LUSA）. It uses Kohonen＇s Self Organ- ized Maps （SOM） and Linear Vector Quantization （LVQ） among other tools to create comprehensive ordering of high number of options. The model uses decision makers preferred locations and environmental data to construct a manifold of the decision＇s attribute space. Then, decision and uncertainty maps are derived from this manifold. An application example is provided using the selection of suitable environments for coconut development in a mu- nicipality of Cuba. CLG-LUSA model was able to provide accurate visual feedback of key aspects of the decision process, making the methodology suitable for personal or group decision making.

A Parallel Line Segment Intersection Strategy Based on Uniform Grids

The line segment intersection problem is one of the basic problems in computational geometry and has been widely used in spatial analysis in Geographic Information Systems （GIS）. Lots of traditional algorithms study the problem in a serial environment. However, in GIS, a spatial object is much more complicated and is considered to be always composed of multiple line segments, and one line segment connects another line segment at its endpoint. On the other hand, along with the advances made in computer hardware, more and more personal computers have multiple cores or CPUs equipped. Thus, to make full use of the increasing computing resources, parallel technique is applied as one of the most available methods. Apparently, the traditional algorithms should be improved to take advantage of the technologies. Under these circumstances, based on the modified uniform grid algorithm, which is adapted to dealing with spatial objects in GIS, this paper proposes a parallel strategy in a shared memory architecture. Also, experimental results are given in the final part of this paper to demonstrate the efficiency this strategy brings.