Research On Nonlinear Transformation Of Digital MAP Based On Region Division

With the advent of the information age,digital maps have been widely used and developed in the fields of military simulation and geographic mapping.However,because digital maps contain a lot of sensitive information,there are strict restrictions on the use of digital maps and cannot be directly used publicly,resulting in the waste of geographic information resources.At present,some linear and nonlinear algorithms for processing images have some shortcomings and defects,such as changing the topology of the map or easily deriving the original map,which is not conducive to protecting sensitive information in the digital map.Therefore,the study of digital map nonlinear transformation method has important theoretical and practical significance.Therefore,the research work of this thesis includes the following three aspects:(1)In this thesis,the Mersenne Twister random number generation algorithm based on chaotic system is proposed.The generated random number is applied to the direction selection,intensity determination,number of region division and determination of the coordinate position of the end point of the nonlinear transformation.The algorithm mainly uses the RC4 algorithm to randomly select a value from the Logistic map or the Chebyshev map of the chaotic system as the initial value to initialize the Mersenne Twister algorithm to generate the random numbers.Experiments show that the generated random numbers are random and unpredictable,which shows the effectiveness of the proposed algorithm.(2)Based on the spatial projection,this thesis proposes a nonlinear transformation model of digital map,which is the core and foundation of this thesis.The model is established to protect the sensitive information from the irreversible and topologically invariant nonlinear transformation of the local sensitive region of the digital map.According to the model,the reasonable range of the projected ray,the boundary correction model and the offset formula of the nonlinear transformation model are theoretically derived,which ensures that the digital map before and after the transformation is reasonable and natural,so that the boundary of the boundary region before and after the nonlinear transformation is reasonably spliced,and the phenomenon of transboundation and misalignment is avoided.(3)In order to protect the sensitive information in the digital map,it is safe and practical.Based on the nonlinear transformation model of digital map and regional division,this thesis proposes a digital map nonlinear transformation algorithm based on region division.Due to the different data models of digital maps,the algorithm is divided into vector map nonlinear transformation algorithm and grid map nonlinear transformation algorithm,which mainly uses region division to divide the transformation region,and independently transform each small rectangular region,so that the algorithm has higher complexity and difficulty in cracking.Experiments show that the nonlinear transformation algorithm has locality,nonlinearity and topological invariance,which further demonstrates the validity and rationality of the model and algorithm.