Research On Digital Watermarking Algorithm For Point Cloud Data Of Geographic Scene

Point cloud of geographic scene paly an important role in 3D city modeling,geographic scene analysis and 3D geographic information system building.Rapidly the computer,lidar technology and UAV tilt photogrammetry technology developing,the collection of point cloud data of geographic scenes has become faster and faster,so a lot of point cloud data of geographic scenes has been produced.These data need to adopt technical means to protect copyright of the data.Digital watermarking technology can embed information in digital data.When these datas leaked or been pirated,the watermark of the data would be useful for copyright identificating or responsibility determining.At present,although digital watermarking algorithms for point cloud data have been studied,there are some shortcomings in data security for point cloud data of geographic scenes.In order to effectively apply digital watermarking technology to the protection of point cloud data of geographic scenes,in this paper,the digital watermarking algorithm for point cloud data of geographic scenes has been studied.The main research contents and conclusions are as follows:(1)Firstly,the basic technology of digital watermarking for point cloud data of geographic scene has been analyzed and studied.Before designing digital watermarking algorithm,this paper first expounds and analyses the methods of data production and characteristics of point cloud data of geographic scenes,and summarizes the characteristics of point cloud data of geographic scenes which other kinds of point cloud data do not have.This paper expounds the data processing means of point cloud data of geographic scenes,and then analyses the attack types that may be encountered by the data.Finally,on the basis of the above analysis,a watermarking model of point cloud data of geographic scenes has been proposed,and the evaluation index of digital watermarking algorithm of point cloud data of geographic scenes has been proposed.(2)Analyzing the stability of point cloud data in the direction perpendicular to the horizontal plane,the conclusion that the ordinate of point cloud data of geographic scene has certain stability has been gotten.Based on the above analysis,a digital watermarking algorithm for point cloud data based on vertical stability has been designed.The algorithm combines the quantization mechanism and the mapping idea,and uses the embedded identification bit to ensure the synchronization of the watermark bits.Experiments show that the algorithm has strong robustness to common type of attacks for point cloud data in many geographic scenes.(3)In order to enhance the ability of digital watermarking of point cloud data of geographic scenes to resist scaling and vertical rotation,the watermarking algorithm for point cloud data has been studied more.In this process,the feature point extraction method,the watermark sequence generation method and the data point coordinate modification method suitable for the algorithm are proposed.At the end of this chapter,the invisibility and robustness of the algorithm have been tested,and the algorithm has been proved to have obvious invisibility and robustness.This algorithm has high robustness and is a blind detection algorithm.(4)With the advent of the era of big data,the storage and computing unit of data has evolved from a single machine to a cluster.In order to comply with the distributed computing trend of geographic big data,the distributed parallel method of digital watermarking algorithm for point cloud data of geographic scene has been proposed.Based on the analysis and research of MapReduce programming model,a distributed parallel computing method for digital watermarking algorithm of point cloud data of geographic scene has been proposed.Distributed parallel computing for digital watermarking algorithm of geographic scene point cloud data is achieved by building Hadoop and writing Map function.Experiments show that the distributed computing method can effectively reduce the computing time of digital watermarking algorithm for point cloud data of geographic scenes.