面向GIS数据共享的概念模型设计研究

Ｇ Ｉ Ｓ 数据共享的主要问题是数据的语义共享。在数据共享的保障基础———技术基础、标准化体系及政策法规体系中,标准化工作最为直接,而其中面向数据共享的概念模型的设计又是最基础性的工作之一。面向数据共享的概念模型设计的主要任务是寻求一种规范化、标准化的约束法则来保障数据的共享,为了保障数据共享的安全性,所设计的概念模型应能提供用于共享的抽象概念,这些抽象概念所描述的是地理概念而非纯空间概念,并应能提供语义抽象机制。采用语义数据模型的方法,提出利用地理特征这一概念作为建模的基本概念。通过一个实例对其应用进行了初步探讨。     

GeoDatabase数据模型及其几何网络的拓扑分析应用

阐述了ArcInfo软件的GeoDatabase数据模型及特点,介绍了GeoDatabase数据模型的几何网络,依据模型几何网络的特点,分析了几何网络在地理信息系统拓扑分析中的应用.     

The Effects of Quality Control on Decreasing Error Propagation in the LandScan USA Population Distribution Model: A Case Study of Philadelphia County

LandScan USA is a 90 m population distribution model that is used for a variety of applications, including emergency management. Models should have a measure of accuracy; however, the accuracy of population distribution models is difficult to determine due to the inclusion of multiple input datasets and the lack of quantifiable, observable (validated) data to confirm model output. Validated data enables quantification of: (1) overall model accuracy and (2) changes in model output at different levels of quality control. This article examines the effect of quality control for two national school datasets incorporated as input in LandScan USA for Philadelphia County, Pennsylvania; which had a local, validated school dataset available. The effect of each stage of quality control efforts utilized throughout the LandScan USA process were assessed to determine what level of quality control was required to have a statistically significant change of the model's population distribution. The typical level of quality control for LandScan USA resulted in 36% of schools being moved to the correct location and 20% of missing student enrollments were found, compared to 87% and 98% respectively for the validated dataset. The costs of increasing quality control resulted in a six-fold increase in labor time; however, the additional quality control did not produce statistically significant improvements in the LandScan USA model. Thus, typical quality control efforts for schools in LandScan USA produced a population distribution similar to the validated level of quality control, and can be applied with confidence for policy, planning, and emergency situations.