基于GIS三维地形的数字高程模型建模实例

简述了数字高程模型的概念,包括数字高程模型的三维地形表面建模原理、方法及技术,并给出使用VC++生成和读取DEM数据的实例。     

基于数字地面模型的公路实时三维动画

研究了一种用数字地面模型和公路设计数据实现实时三维动画的方法。首先利用Delauany三角化方法构造数字地面模型，然后将公路设计数据与数字地面模型进行叠加。为解决叠加过程中的相容性问题，提出了先将地界约束边界线插入Delauany三角形网格，然后重新三角化的方法。为加快渲染速度，提出了多分辨率显示和网格数据结构相结合的加速措施。文中的方法在实践中得到了验证。     

一种基于四叉树结构的动态多分辨率地形模型

结合油田可视化项目,文章根据三维地形可视化中利用四叉树存储DEM数据的方法,提出了一种与视点相关的动态多分辨率地理模型的构造算法,主要讨论了该模型的多分辨率地形表示机制以及动态地形简化方法和评价函数等问题,试验结果表明,文中的算法达到了预期目的,能应用于地形场景的三维可视化和漫游。     

Parallel Processing for Terrain Analysis in GIS: Visibility as a Case Study

The application of parallel processing to computationally intensive GIS problems has been advocated and illustrated by many researchers over the last twenty years. Despite this, GIS users have been slow to capitalize on the potential which the technology offers. Whilst todays processors are adequate for the majority of GIS uses, some applications are too processor-intensive to be deemed viable for serial machines. This is particularly true of many digital terrain modelling applications, which has been the primary focus of parallel processing in GIS to date.This paper considers the problem of parallelizing line-of-sight (LOS) calculations in determining the visibility indices of entities such as elevation vertices in a digital terrain model (DTM). This is a requirement of site selection for a particular development, especially if visibility, or more specifically, visual intrusion is likely to be a key factor in gaining planning approval. To demonstrate the simplicity and applicability of parallelizing such GIS problems, this paper presents some parallel approaches in an efficient data organization, framework using a Transputer network. Speed-up performance can be increased by a factor of twelve using a simple network of twenty Transputers. As vast quantities of spatial data become available, particularly DTMs at larger scales and denser resolution, the demands for parallel processing will inevitably increase. It is hoped that the continued experiences of todays researchers at applying parallel processing to well-defined problems will benefit the GIS users of tomorrow.     

夷平面数字地形模型的生成、显示与分析初探——以美武高原为例

以甘南美武高原太子山地区典型夷平面为例,利用遥感与计算机技术,对夷平面三维数字地形模型的生成、显示与定量分析方法进行了探索,为夷平面显示的直观性、准确性和定量化研究提供一种新的途径。并利用这一方法,对美武高原典型残余夷平面的分级、坡度、坡度变化率、相对高差等反映地貌形态的数量特征进行了计算、统计与分析,第一次提出了该地区残余夷平面的准确数值特征,为进一步深入研究打下了坚实的基础。     

设计特征模型到分析特征模型的自动转换方法

针对有限元分析建模的需求,提出一种将工程零件的设计特征模型自动转换为相应的分析特征模型的方法.首先将设计特征模型分解为所有正特征剩余体的集合,然后从各正特征剩余体中分解出一组扫成体和非扫成体,再采用基于二维轮廓的方法从各扫成体中确定出候选分析特征区域,最后通过合成候选分析特征区域得到真正的分析特征区域,并在此基础上生成分析特征和分析特征模型.实验结果表明该方法是有效的.     

高职院校组织管理模式影响数字校园建设策略分析

本文在比较分析不同时期我国高职院校组织管理模式的基础上,结合智慧校园、云计算平台等校园信息化建设的理论,深入分析了其对高职院校数字校园建设的影响,提出我国未来高职院校数字校园建设的策略是：依托统一的云平台,结合院校的管理现状,建设行政管理、学术管理、后勤管理三大业务系统平台。     

Six Ways from Sunday: Approaches to Indexing Digital Text Images

In 1994, the Andrew W. Mellon Foundation funded a joint project undertaken by the Center for Research Libraries (CRL) and the Latin American Microfilm Project (LAMP) to scan and index over three-hundred thousand pages of microfilmed Brazilian Government Documents for the Internet. Due to the collection size, format, language and poor physical condition of the text, entering this overwhelmingly textual collection as full-text was prohibitively expensive. Instead the documents were scanned as images, thereby maintaining the intellectual content of the collection, but losing the dynamic searching capabilities inherent in full-text databases. A combination of indexing approaches was used to provide access to these documents. Indexing (table-of-contents, pagination and subject indexes) found in the documents were recreated to give users access to the documents. A controlled vocabulary was established to index a portion of the database. The factors of costs, user feedback and available technologies all influenced the choices of the five indexes ultimately utilized. This paper will describe and comment on the strengths and weaknesses of the various indexing approaches taken to access the images within this database.     

从四个类比看如何建立高质量、易维护的用例(Use Case)模型

用例模型在软件开发中占有重要的地位。类和用例都属于类元范畴,具有可比性。该文通过4个类比,由一般较熟悉的,应用于低粒度类设计中的技术、方法和原则过渡到应用于高粒度用例建模的技术、方法和原则,并进一步结合它们给出了用例建模过程的一般步骤。     

The Decoupling of Value Creation from Revenue: A Strategic Analysis of the Markets for Pure Information Goods

Information and telecommunications technologies have profoundly altered the distribution channels available for a wide range of goods and services. In this paper we analyze a particular class of products, information goods and develop a first framework for predicting which information goods are most likely to see their production, distribution, and consumption patterns altered by the net, which are likely to see shifts in power and profitability, and which are likely to remain unchanged for the foreseeable future. We focus on music and news as a selected couple of very different information goods industries that follow two very different trajectories. Our results suggest that the power structure in news distribution is unlikely to be transformed rapidly. In contrast, the power structure in music is transforming rapidly. Star acts no longer need their record labels to certify their music to their fans, and digital production and distribution have reduced or eliminated the value of other assets owned by the record companies. The framework we use to analyze these two industries can readily be applied to a range of others ... from the production of television soap opera series to the publication of academic journals in polymer chemistry.     

How to Verify a Safe Real-Time System: The Application of Model Checking and Timed Automata to the Production Cell Case Study*

The formal verification of a real-time system requires either a proof theoretic or model theoretic approach. Both being applicable to a model of the proposed behavior of the concurrent real-time system. This paper evaluates the use model checking and timed automata by their application to an adaptation of the Production Cell case study. The Uppaal tool is used in this evaluation. The modeling aspects were found to be straightforward, but to accomplish the necessary model checking required some knowledge of the underlying process. Nevertheless, the conclusion of the study is that these techniques are generally applicable and be can be undertaken in an engineering context without detailed domain knowledge of the model checking technique.     

Semi-automatic classification of tree species in different forest ecosystems by spectral and geometric variables derived from Airborne Digital Sensor (ADS40) and RC30 data

This study presents an approach for semi-automated classification of tree species in different types of forests using first and second generation ADS40 and RC30 images from two study areas located in the Swiss Alps. In a first step, high-resolution canopy height models (CHMs) were generated from the ADS40 stereo-images. In a second step, multi-resolution image segmentation was applied. Based on image segments seven different tree species for study area 1 and four for study area 2 were classified by multinomial regression models using the geometric and spectral variables derived from the ADS40 and RC30 images. To deal with the large number of explanatory variables and to find redundant variables, model diagnostics and step-wise variable selection were evaluated. Classifications were ten-fold cross-validated for 517 trees that had been visited in field surveys and detected in the ADS40 images. The overall accuracies vary between 0.76 and 0.83 and Cohen's kappa values were between 0.70 and 0.73. Lower accuracies (kappa < 0.5) were obtained for small samples of species such as non-dominant tree species or less vital trees with similar spectral properties. The usage of NIR bands as explanatory variables from RC30 or from the second generation of ADS40 was found to substantially improve the classification results of the dominant tree species. The present study shows the potential and limits of classifying the most frequent tree species in different types of forests, and discusses possible applications in the Swiss National Forest Inventory.