gis的简单绘图功能以及实现分图层管理，具体的代码部分还是有说明的，能够看懂，希望随大家有帮助-gis mapping functions and the easy implementation management of sub-layers, or a specific part of the code have described, be able to understand, I hope everyone has to help with

非常棒的最新技术的CAD绘图系统代码，是教学性质的，实现了CAD必须的较全面的技术。-Great in the latest technology CAD drawing system code, is a pedagogical nature, achieved a CAD must be more comprehensive technology.