【作者】 王志伟；

【导师】 朱长青；

【作者基本信息】 解放军信息工程大学 ， 地图学与地理信息系统， 2011， 博士

【摘要】 DEM数据是国家基础设施建设和地球科学研究的支撑性成果之一,在国家经济、国防建设中占有十分重要的地位。随着数字化和网络化的飞速发展,DEM数据的存储、传输、复制都变得非常方便快捷,其安全和版权问题也日益凸显,侵权、泄密、非法传播与使用等行为屡禁不止,仅依靠目前现行的安全保密措施和法律法规,根本无法有效阻止与打击各种非法行为。数字水印技术作为一种新兴的信息安全技术,为DEM数据的安全保护提供了一种切实可行的解决途径。数字水印技术是在数据中嵌入秘密水印信息,并使其成为源数据不可分离的一部分,由此来确定版权拥有者、跟踪侵权行为、认证数字内容等,从而为DEM数据的安全使用提供强有力的技术支撑。本论文结合DEM数据特征、精度和应用要求,对DEM数字水印技术进行了系统研究,主要研究成果如下:(1)建立了一种实用的栅格DEM数字水印模型——基于映射机制的栅格DEM数字水印模型。该模型建立了水印信息序列与栅格DEM高程值之间的映射关系,解决了两者之间的变化不同步问题,可有效增强水印算法的抗裁剪能力和抗高程平移能力;同时,该模型具有水印容差自主控制机制,可根据实际精度需求,自主调节水印容差大小,以满足DEM数据精度要求及水印算法对不同噪声的抵抗能力。(2)根据所建立的栅格DEM数字水印模型,分别提出了一种抗裁剪的DEM水印算法和一种抗高程平移的DEM水印算法。这两种算法均采用量化思想对DEM高程数据进行水印信息调制,达到了盲检测的目的。同时,运用所建水印模型的特性,实现了水印算法在数据裁剪、高程平移、数据删除、随机噪声等方面的强鲁棒性。(3)结合DEM地形特征,提出了一种顾及地形特征的栅格DEM水印算法。该算法继承了抗裁剪、抗高程平移水印算法的特性,并通过对DEM地形因子的分析、归类,提炼了其中最为基础的两大地形因子——坡度和坡向,在水印嵌入过程中,充分考虑水印嵌入对坡度坡向的影响,运用DEM误差分析理论,制定顾及坡度坡向因子的水印嵌入策略和方法,最大限度的降低了水印嵌入对DEM地形分析的影响。(4)建立了一种实用的不规则三角网DEM数字水印模型——基于映射机制的不规则三角网DEM数字水印模型。根据此模型,可分别建立水印信息序列与高程坐标、平面坐标的映射关系,解决水印信息与载体数据的变化不同步问题,有效增强了水印算法的鲁棒性。(5)根据所建立的不规则三角网DEM水印模型,提出了一种顾及拓扑特征的不规则三角网DEM数字水印算法。该算法选择离散高程点的X坐标集作为水印信息的承载通道,通过平面坐标建立离散高程点与水印信息序列的映射关系,采用量化调制机制将水印信息嵌入到X坐标集中,对高程数据不再进行水印嵌入,保持了DEM数据的高程精度。在水印嵌入过程中,为保证嵌入水印后不规则三角网拓扑关系的正确性,建立了拓扑约束条件。(6)根据所建立的不规则三角网DEM水印模型,提出了一种基于点重要度的不规则三角网DEM数字水印算法。该算法继承了顾及拓扑特征的DEM水印算法的特性,同时,又建立了点重要度的水印嵌入约束条件,仅对离散高程点中的部分“重要点”进行水印信息的嵌入,以缩减水印嵌入所引起的数据改变比例,达到“以较小误差代价获得较优鲁棒性”的目的。(7)结合DEM误差分布规律,针对本文提出的模型和算法,运用概率统计理论,对数字水印生成、嵌入过程进行分析,推导了水印嵌入对DEM数据精度的影响公式,从理论上分析了水印嵌入对DEM数据精度的影响。更多还原

【Abstract】 DEM data is one of the supportive achievements in the field of national infrastructure and earth science research, and plays a significant role in national economy and defenses. With the rapid development of digitization and network, the storage, transmission and replication of DEM data is very convenient, so the security and copyright issues have become increasingly salient. It has been recognized that the current security laws and technologies are inadequate for dealing with the behavior of infringement, disclosure, illegal dissemination and usage.Digital watermarking technology is a new information security technology, and can provide a feasible and practical solution for the copyright protection for DEM data. Digital watermarking is the process of embedding secret information into digital data, and later the information can be extracted or detected for a variety of purposes such as copyright prevention, ownership authentication, infringement tracking and tamper detection. Digital watermarking is being deemed essential to provide a strong technical support to the legitimate use of DEM data.In this paper, combining the feature, accuracy and application requirements of DEM data, the digital watermarking of DEM is systematically studied. The main results are as follows:(1) A practical digital watermarking model of raster DEM is proposed based on mapping mechanism. By this model, a mapping relationship is established between watermark sequence and elevation coordinates of raster DEM so as to resolve the no synchronization problem of each other, which can effectively enhance the robustness of watermarking algorithm in the data clip and the elevation translation. Simultaneously, this model can independently control the size of mapping tolerance to meet the accuracy requirement of DEM data and the robustness of watermarking algorithm.(2) Two algorithms are put forward based on the proposed digital watermarking model of raster DEM. The two algorithms are blind watermarking algorithm by quantification mechanism. And by the features of this proposed model, the two algorithms have the strong robustness in data clip, elevation translation, data deletion and random noise.(3) A digital watermarking algorithm of raster DEM is proposed considering the terrain features. This algorithm inherits the characteristics of the above two algorithms. In this paper, the slope and aspect are considered as two basic terrain factors. So in the process of watermark embedding, the slope and aspect are taken into account. And then using the theory of DEM error, a reasonable strategy of watermark embedding is developed to minimize the impact of watermark embedding on terrain analysis.(4) A practical digital watermarking model of TIN-DEM is established based on mapping elevation coordinates can be established, and the mapping relationship between watermark sequence and plane coordinates can also be established. This mapping relationship can effectively enhance the robustness of watermarking algorithm.(5) An algorithm considering topological features is put forward based on the established digital watermarking model of TIN-DEM. This algorithm embeds the watermark information into the X coordinates by quantification mechanism. So this algorithm can effectively maintain the elevation accuracy of DEM. In the process of watermark embedding, some constraint conditions are proposed in order to ensure the correctness of topology.(6) According to the importance of point, a digital watermarking algorithm of TIN-DEM is proposed. This algorithm inherits the characteristics of the algorithm considering topological features. And according to the importance of point, some constraint conditions are established in order to minimize the impact of watermark embedding on DEM accuracy. Simultaneously, this algorithm can achieve the purpose of“obtain the superior robustness by the small error cost”.(7) According to the theory of probability and statistics, the impact rule of watermark embedding on DEM accuracy is analyzed combining the error distribution of DEM data and the algorithms proposed above. Meanwhile, the impact formula is derived theoretically.更多还原