Three Rules Suffice for Good Label Placement

The general label-placement problem consists in labeling a set of features (points, lines, regions) given a set of candidates (rectangles, circles, ellipses, irregularly shaped labels) for each feature. The problem arises when annotating classical cartographical maps, diagrams, or graph drawings. The size of a labeling is the number of features that receive pairwise nonintersecting candidates. Finding an optimal solution, i.e., a labeling of maximum size, is NP-hard. We present an approach to attack the problem in its full generality. The key idea is to separate the geometric part from the combinatorial part of the problem. The latter is captured by the conflict graph of the candidates. We present a set of rules that simplify the conflict graph without reducing the size of an optimal solution. Combining the application of these rules with a simple heuristic yields near-optimal solutions. We study competing algorithms and do a thorough empirical comparison on point-labeling data. The new algorithm we suggest is fast, simple, and effective. Received December 21, 1998; revised October 13, 1999.     

合理设计课堂教学创建制图精品课程

阐述了工程制图课程课堂教学过程设计的指导思想,分析了不同教学内容所采用的教学方法和手段,指出了制图教学实践的过程和知识结构特点,提出了合理设计制图课堂教学过程的方法。     

用微机绘制织物应变图

本文用直角坐标量的测定,来计算织物受力时各部分的应变,然后根据应变的实际大小,借助计算机的绘图仪,可在织物上绘出若干个具有不同应变值的分布图。     

测绘制图在公路自行车运动中的应用

结合首届环中国国际公路自行车赛-石家庄站的情况,以公路自行车运动中的三张比赛用图(比赛线路图、线路海拔图、最后3 km线路海拔图)的制作为例,简述测绘与制图在该项运动中的应用.     

ISO: A Fortran IV Program for Generating Isopleth maps on Small Computers

The construction of computer-generated isopleth maps has been limited generally to large computer programs such as SYMAP and AUTOMAP II. These programs may require machines with large amounts of memory. Large machines are not available to many potential users. This paper describes the program ISO, which is designed to create isopleth maps on small- and medium-size computers. ISO complements the CMAP program developed to produce chloropleth maps on small computers and employs many of the features used in CMAP. It also provides some additional features such as limited map cosmetic capability, internal storage of scan lines for multiple map runs, and greater operational convenience in establishing map categories, symbols, and text. Proximal maps also can be generated by ISO.     

坚持工程识图能力培养 提高学生工程实践能力

当前工科院校教育面临的关键问题是如何提高学生的工程实践能力。结合我校过程装备与控制工程专业的工程实践能力培养的实践教学体系,我们通过坚持工程识图能力四年不断线培养,切实有效地提高了学生的工程实践能力。     

土地利用总体规划数字线划地图的编制与质量控制

以绵阳市城市发展规划区土地利用总体规划数字线划地图编制为例,探讨了基于MapGIS数字线划地图的编制流程,分析了数字线划地图的误差来源和纠正原理,并对数字线划地图数据质量控制方法进行了探讨。     

道路工程制图课程的改革与建设

在总结公路与城市道路专业教学改革试点工作的基础上,阐述了道路工程制图课程改革与建设的基本思路及主要措施。     

制图课程教学方法改革初探

在总结教学实践的基础上,阐述了在制图教学中教学方法改革的探索。     

Location‐dependent generalization of road networks based on equivalent destinations

Suppose a user located at a certain vertex in a road network wants to plan a route using a wayfinding map. The user's exact destination may be irrelevant for planning most of the route, because many destinations will be equivalent in the sense that they allow the user to choose almost the same paths. We propose a method to find such groups of destinations automatically and to contract the resulting clusters in a detailed map to achieve a simplified visualization. We model the problem as a clustering problem in rooted, edge‐weighted trees. Two vertices are allowed to be in the same cluster if and only if they share at least a given fraction of their path to the root. We analyze some properties of these clusterings and give a linear‐time algorithm to compute the minimum‐cardinality clustering. This algorithm may have various other applications in network visualization and graph drawing, but in this paper we apply it specifically to focus‐and‐context map generalization. When contracting shortest‐path trees in a geographic network, the computed clustering additionally provides a constant‐factor bound on the detour that results from routing using the generalized network instead of the full network. This is a desirable property for wayfinding maps.