“4D”技术及其应用

介绍“４Ｄ”（即数字地面模型、数字正射影像、数字栅格地图和数字线划地图）系列产品的生产流程、关键技术、及其在耕地保护、防灾减灾救灾和城市规划等方面的应用方法。     

矢量图形与影像图像一体化实现

本文在阐述影像金字塔相关理论（构建方法、影像切割等）的基础上,采用VC2005编程实现了在同一GIS系统中进行矢量数据和栅格数据叠加显示的功能模块。该模块可确定是否加载影像,并根据当前矢量图显示范围自动加载不同分辨率的影像图。     

A comparison of raster-based travel time surfaces against vector-based network calculations as applied in the study of rural food deserts

While the term food insecurity is gaining popularity in contemporary literature, there is debate as to how tenets of this phenomenon can be quantitatively measured. One of these tenets, proximity to food resources, which is used to measure food deserts, can be measured within a digital GIS (Geographic Information System). Metrics such as Euclidean and network distance represent planimetric distance measurements between locations and resources, but do not truly represent the empirical cost that serves as a barrier, most notably time and/or money, to those who must decide to travel to these resources. While the vector data model has been the standard by which these calculations are done within a GIS, raster-based travel time surfaces can serve as a faster, replicable and scalable alternative. However, little research has been done to test the efficacy of these surfaces and their alignment with vector-based network calculations. In this research, we developed two travel-time surfaces for a rural region in southeastern North Carolina. One represented travel times to grocery stores and while the other represented travel time to convenience stores. We found that the travel times derived from this surface were statistically consistent with vector-based counterparts for sample sizes at a 95% confidence. When utilized correctly using an appropriate scale and spatial resolution, these surfaces have the potential to be effective tools in the study of food deserts.     

基于栅格数据的最佳路径分析方法研究

讨论了基于栅格数据的最佳路径分析方法。该方法利用Dijistra算法的基本思路和“节点／联系”模型,首先通过8邻域像元算出每个像元到源像元的最小权距离,然后计算后向连接值,最后根据累积权距离栅格和后向连接栅格计算出最佳路径。本结合实例讲述了应用Arc/Info的GRID模块进行最佳路径分析的方法和步骤,并提出了改进算法的研究思路。     

土地利用空间数据尺度转换中的精度损失分析

在地理信息系统的支持下,利用两种矢栅转换原则对土地利用空间数据进行尺度转换,并对不同栅格大小下,各种土地利用类型的精度损失特征进行了分析.研究结果表明: (1)面积最大值原则(RMA)下,栅格大小< 80 m时,其精度损失均< 2%; 中心值原则(RCC)下,栅格大小< 160 m时,其精度损失均< 2%.(2)在栅格大小为800 m时,水域在面积最大值原则下的精度损失超过50%,在中心值原则下的精度损失超过20%.(3)在空间粒度逐渐增大过程中,面积最大值原则下生成的栅格数据相对误差较大,各地类精度损失的绝对值与栅格大小之间成正相关; 中心值原则下,各地类的相对误差较小且复相关系数均很小,表现出很强的随机性.     

基于栅格图片的建设用地图形辅助审查系统

本文介绍了在土地利用现状等基础数据库未建成的情况下,如何利用GIS技术实现栅格图件配准、拼接,界址点坐标无缝展示以及栅格图片的局部矢量化和面积量算等,为建设用地审查提供辅助依据,以提高用地审批的科学性和工作效率。     

基于栅格数据的局部奇异性分析迭代方法及其软件实现

近些年,弱缓化探异常识别已成为成矿预测和勘查评价中十分关键的问题。多重分形理论的局部奇异性分析因其崭新的思路、简便的方法、优良的效果而在弱缓异常识别中受到广泛关注。在深入剖析局部奇异性分析基本思想及计算方法的基础上,引入正规化尺度参数L,提出了迭代方法来改进局部奇异性指数的估值。给出了奇异性迭代算法并用C＋＋编程实现,软件功能强劲,操作灵活,不仅适用于各向同性情形,还适用于各向异性尺度的奇异性计算和方向性奇异性计算。软件的动态链接库版本已在Geo DAS矿产资源定量预测专业软件中应用。