基于SVG在线应急标绘符号的设计与实现

Design and Implementation of Online Emergency Plot Symbol Based on SVG

根据当前WebGIS发展趋势和应急符号在Web地图上进行标绘的需求,在分析几种标绘编程语言的技术特点后,研究并设计了基于SVG（scalable vector graphics）应急符号在线绘制机制并对地理坐标转换及非规则应急符号控制点的生成这一关键点作了阐述。在分析符号特征的基础上主要把应急标绘符号分为点符号和函数符号两种类别并且通过三层继承绘图机制（基本符号构建类-具体绘制类-编辑类）进行标绘。结果表明：该机制可以较好的实现交互式应急符号的在线标绘且能够满足相对复杂的应急规则及多变的现场环境,基本达到预期要求,其中点符号可通过用户定制模版无限扩展,对于一些复杂应急符号则以JavaScript API的方式提供给用户以便于制图人员和相关开发人员的使用,简化了开发的难度,提高了开发效率。

This paper analyzes the technical features of several programming languages according to the current development trend of WebGIS and the requirements of emergency symbols plotting on the Web map,designs the online mapping mechanism based on the SVG emergency symbol,and interprets transformation of the geographical coordinates and the generation of the control points of the irregular emergency symbols.Then,based on the ananlysis of the symbolic features,this paper mainly divides them into two category：emergency plotting symbols and functions and plots them through three layers of inheritance mapping mechanism（basic symbol building class-specific drawing classes-editor）.Results show that this mechanism can better realize the interactive emergency sign online plotting,can meet the emergency rule and relatively complex and changeable field environment,and achieves the expected requirement：the dot notation by custom template can extends infinitely,can reduce the development difficulty by providing user with some complex emergency signs in the form of a JavaScript API for drawing the use of personnel and related developers,and can improve the development efficiency.