Chen Yanming

A Novel Method of Buffer Generation Based on Vector Boundary Tracing

Utilizing the property that the distances from all points located on the borderline of buffer zone to corresponding buffer target are the same, this paper presents a novel method of buffer generation based on vector boundary tracing. The new method can avoid complex vector calculations, such as line and curve segment intersection, clipping and recombination, the closure of borderline and so on, and also has an advantage of high precision the same as all existing vector-based algorithms. The main steps of this algorithm include: (1)Generate the initial tracing point set located on the borderline of buffer zone; (2)Obtain an integrated and closed borderline by tracing these points; (3)Construct the area targets on the basis of these closed borderlines. The test results and analysis indicate that this algorithm has a great advantage in the aspects of decreasing EMS memory consumption and improving calculation accuracy, and its computational efficiency can fully meet the demand of usual application in GIS. Furthermore, the principle of boundary tracing in the algorithm has a potential for further being promoted and used to design related spatial analysis algorithms.

The Module Design of Map Projection Transformation Based on Object-Oriented

Map projection transformation is the important part of cartography, and plays the key role in GIS. With the continuous updating and improvement on geographical data, it has become very urgent to meet the demand of assimilating geographic information by map projection transformation. Projection transformation is one of the essential models for lots of widely used GIS software and the development of GIS software available. In the paper, the object-oriented method is introduced to realize the module design of map projection transformation, the process of design and implementation is discussed in details, and advantages of this method applying to map projection transformation is also analyzed. In all, the method is beneficial to the implementation of fast and efficient programming, and has such advantages as strong scalability and easy maintenance.