中文摘要：

地理数据库是地理信息系统的基础，也是数据生产者的宝贵财富．因此，如何利用数字水印技术保护地理数据库的版权成为一个亟待解决的问题．提出一种高鲁棒的、保持形状的、支持盲检的地理数据库水印方法．利用面类地物的平均特征距离的最高矗有效位作为鲁棒地物标识，并将所有地物划分到若干分组中，采用可变步长量化调制方法嵌入水印信息，并通过轻微修改地物的面积体现水印的嵌入．为确保算法的安全性，水印嵌入过程中地物和分组间的归属关系、每个地物上拟嵌入的水印位和相应的步长均基于用户密钥计算得出．实验证明，该方法具有良好的鲁棒性，能有效抵抗平移、旋转、化简、噪音附加、顶点插值、裁剪、元组增加和元组修改攻击．而且，在数据可用性范围内，随着水印强度的增加，算法鲁棒性随之提高．

英文摘要：

Geographical databases, as one kind of the most important infrastructure of geographical information system, are great treasure of data owners. How to protect the copyright of geographical data effectively using digital watermarking is a critical issue. In this paper, we propose a robust, shape-preserving and blind watermarking method. We compute mean feature distance for each polygon and choose h most significant bits of mean feature distance as the robust identifier of one polygon. All polygons are partitioned into several groups based on their identifiers. Quantization modulation technique with variable steps is exploited to hide watermark into all polygons whose areas are slightly modified to derive watermarked geographical database. To ensure the security of the proposed algorithm, the polygon-group assignment, the watermark bit to be embedded in each polygon and every variable step are all algorithmically determined under the control of a private key known only to the owner of the data. Experimental results show that the proposed watermarking method has good performance and is resilient to translation, rotation, simplification, noise addition, vertices interpolation, cropping, tuple alteration and insertion attacks. Moreover, within the usage range of the geographical data, the robustness of the proposed method is improved with the increase of the watermark strength.