Research on Great Wall section protection and user VR experience innovation based on GIS data visualization

VR technology can enable users to be in a realistic virtual environment, thus bringing them an immersive experience. It has great charm and can effectively display scenes that are difficult to reproduce in real life. It can also be used in education and other fields. It has a wide range of applications and can bring great convenience. Under this background, this paper introduces GIS data visualization technology to complete the expansion of VR technology and apply it to the Great Wall section protection research project. This paper has improved a kind of VR system, which can meet the needs of human–computer interaction and create virtual avatars to achieve two-way communication between human and VR experience environment. This system design has the advantages of simple use and powerful functions and is also the design goal of VR experience technology itself. The ease of use of the system is reflected in the visual clarity of interface interaction and system response speed. The practicality is reflected in the stability of system operation and the time required for users to complete feature functions. The security is reflected in the degree of protection of private data. The simulation results show that the system can effectively reduce the magnitude of data after processing and compressing the data set, thus reducing the processing time. Compared with the original processing method, it can be seen that the system improves significantly. By traversing the original dataset, the array can be effectively drawn, which greatly reduces the system processing time and improves the efficiency. In this paper, GIS data visualization technology and VR technology are integrated to complete the research of the Great Wall section protection project.


Introduction
In the mid-1970s, American psychologists put forward VR Immersion Theory, also known as Flow Theory, which can describe the immersive state that people fall into when they concentrate on doing something [1].When the experiencer enters the state of " ow of mind", their body and mind are immersed in the long silent ow, and all their consciousness is concentrated in the present, so they can not feel the interference of the outside world and the passage of time.The sense of satisfaction and excitement related to " ow of heart" will upgrade the user's experience process to pleasant psychological satisfaction and spiritual pleasure [2].The premise of using virtual reality technology is to complete the creation of graphics system and interface equipment based on computer technology, so as to achieve the creation of an immersive virtual environment that can interact with users [3].The core of virtual reality technology is computer technology, supplemented by other technologies, which can simulate a realistic virtual environment and reproduce some senses, such as vision and hearing, to a certain extent, so that users can get a feeling and experience close to the real world [4].The user interface design of VR system is usually divided into two parts: the display of information and functions, and the presentation of virtual scenes.First of all, there is no difference between the design of information content and function display of the system and the user interface design of traditional media, mainly including: color, text, icon, image, composition, layout, etc.The common ways of information function layout of the system are divided into the following types: display type, palace type, table type, drawer type, decentralized type and Cover ow type [5].

Related Work
The literature uses AHP fuzzy method to create a set of user immersion evaluation models.By applying this model, users' experience state when using virtual devices can be effectively evaluated, so as to determine the membership of evaluation indicators, and the comprehensive evaluation results can be determined based on this value and the principle of maximum membership, so as to better express users' sense of experience, so as to complete decision support based on such data [9].The literature analyzes the advantages and potential of immersive VR technology based on theory; In the applicability analysis, the operational changes and new application scenarios brought by immersive VR technology to today's architectural space experience and evaluation are studied.The literature shows that immersive VR technology can be used as a supplement to traditional building space evaluation methods [10].On the basis of theoretical analysis and research, this paper studies how to use immersive VR technology in architectural experience and space evaluation through experiments [11].Based on the analysis of the development of virtual reality technology at home and abroad, the literature proposed and improved the visual design of virtual assembly platform of multi-channel VR system for practical task objectives [12].
The main design goal of the system is to create a virtual assembly environment.The literature analyzes and classi es the experience elements of VR interface design based on immersive experience, mainly including four main parts: creative expression, interactive form, virtual realm and emotional experience, and puts forward corresponding VR interface design guidelines [13].According to the guiding principles of VR interface design, speci c application interfaces are designed in the virtual VR classroom.The practice followed the complete process and design ideas of product design, and nally produced a complete set of VR interface based on immersive experience and carried out theoretical analysis, followed by display con rmation [14][15].
3 Gis Data Visualization Technology

Framework introduction
Topographic GIS data includes contour DLG and regular grid DEM data, which can be used to generate TIN to obtain large-scale 3D terrain scale modeling and rendering.
The 3D terrain visualization structure of this paper is shown in Fig. 1, which is mainly divided into two stages: terrain visualization model construction and scene rendering.After data collection, the system will draw.In order to reduce the workload in the drawing phase, quadtree can be used to organize terrain blocks.Based on the idea of feature point selection, this paper introduces Laplace operator.For surface S, Laplace transform is de ned as: Since Laplace operator is a differential operator, it can represent the change rate of each point on the surface S.This feature makes Laplace operator widely used in image processing and other elds.
According to the result of Laplace transform, you can choose to be greater than the threshold ε To meet the requirements of feature point selection.Laplace transform can easily remove areas with at terrain or low rate of change.Apply Laplace operator to discrete terrain sampling data, discretize the above equation and add diagonal terrain in uence.For terrain block Bi, its screen error can be calculated by the following formula: 2 Considering the maximum error of block division, the above equations are simpli ed and decomposed.
Obtain the maximum screening error of the plot δ And ε The relationship of is as follows: 3 This research work uses an independent quadtree data planning thread, as shown in Fig. 2. Suppose you cut the scene and select the terrain block in the current view, and call the gray node "active node", which can effectively meet the real-time rendering requirements in the actual roaming process.

Model construction
The general structure of GeoServer can be divided into six parts: workspace, store, layer, grouplayer, SLD (Style Layer Descriptor), OGC speci cation, etc.As shown in Fig. 3.
The publishing process is shown in Fig. 4.
The data set used in this paper limits the deformation monitoring data to a certain time range.The data capacity of this project is very large, with an average of more than 600000 point cloud data.Cloud data has many characteristic dimensions, and the dimensions are complex and different.Therefore, the above data sets need to be processed to obtain information that can be used for visual display.The measurement principle of InSAR monitoring is mainly through interferometric phase processing.First, two SAR images are obtained by parallel observation of the target to be observed by two satellites.Then, the geometric relationship between the target and the two antennas is used to interfere with the phase difference between the complex images, generate an interferogram, and analyze it to obtain the elevation and other related information.The expression of differential interference component is: The control input mode is related to the size of the screen, which determines the number of particles per unit area of the screen, thus determining the process of the particle system. 13 The particles will die, or they will exist all the time, causing the system to collapse, so the particles have a life cycle.If the lifecycle is 0, the particles are removed from the system.The life cycle of particles is shown in Fig. 6. "Need" refers to the speci c physiological and psychological requirements that organisms feel for objective things in the process of survival and development.For example, people need food when they are hungry and water when they are thirsty.But the actual human needs go far beyond food and water.In addition to the physical needs for speci c materials, human beings also have abstract needs for thought, culture, art, morality, etc.This spiritual satisfaction is called spiritual needs.

Model simulation
Functional practicability is the direct embodiment of the usability of VR interface design.The design must realize some functions and solve some problems.The functions of VR interface mainly include information acquisition, navigation acquisition, interactive control of virtual environment, etc. Information retrieval is the main function of the interactive interface.It provides users with information in the form of text, pictures, videos and other forms, and is the core content of the VR interface; Navigation and retrieval functions depend on the main functional requirements of VR applications, while the VR interface structure is complex, which requires the use of navigation and retrieval functions to divide the interface space and fold application information, but VR applications with single functions in the interface (such as scene roaming VR applications) generally do not need navigation and retrieval functions; VR interface is the interface between user and computer.And because the interactive VR interface has the characteristics of dual interaction, it needs to complete the dual interaction between the user and the virtual image, as well as between the virtual image and the virtual environment.Ease of use, security and reliability are also the main contents of system functional requirements.The standards of practicality and convenience lie in the intuitiveness and clarity of interface functional classi cation, the response speed of interaction process and the time required for users to complete goals.The system interface can also re ect security and reliability, such as error and crash frequency, privacy protection, etc.The evaluation indicators of VR interface's essential functions are shown in Fig. 7.
With the continuous development of the functional complexity and application popularity of VR products, the interactive interface of the VR system should also be constantly updated and gradually become the best design, providing more effective and reliable guarantee for the functional production of the VR interface.The principle of system usability interaction design is discussed based on the principle of multiple interactions.The functional requirements of VR interface are closely related to its use, and its usability includes usefulness and ease of use.Availability refers to whether the interface has realized appropriate interaction functions and is compatible the contents of system functions.Ease of use refers to the interaction e ciency and learnability between the user and the interface, which corresponds to the intuitive, clear and responsive requirements of simple suggestions.Therefore, to improve the interaction function of VR interface is to improve its practicality and ease of use.

Process design
In virtual reality technology, the content of the display channel is determined by the position and direction of the viewpoint and the setting of the view trunk, as shown in Fig. 8.

Protection and development strategy of the Great Wall section
castle is distributed along the Great Wall, which passes through the city.Some castles are located in sparsely populated mountainous areas or areas with inconvenient transportation; Some are located in densely populated villages.It is necessary to further clarify the responsibility of municipal government departments at all levels to protect the castles along the Great Wall.We should establish a proper accountability system for castle protection, formulate appropriate reward and punishment policies, and let the whole people participate in the protection of the Great Wall and the castle.
Any historical building can not be separated from the surrounding environment, so while protecting the Great Wall and the castle, we should also pay attention to protecting the surrounding ecological environment.The ecological environment around the castle, the castle itself and the castle buildings together constitute the historical landscape of the Great Wall Castle.The local government should take reasonable and scienti c planning measures and strengthen management to ensure the sustainable development of the natural ecological environment around the castle.
The protection of the Great Wall Castle is accompanied by the problem of raising funds.The funds of many castle villages are mainly spent on the construction of villages, and there is no time to consider castle maintenance.Therefore, the local government can increase the investment in the maintenance of the Great Wall Castle and use the castle's cultural and historical resources to stimulate the local economic development.
To build a wall on the city wall, residents must rst negotiate for relocation, and their living arrangements must be arranged in other areas of the village.Then the houses that damage the city wall will be demolished, and the damaged city wall must be treated according to the current situation, and the houses that damage the resistance of the city wall must be properly treated.Problems such as cracks caused by building construction must be lled with suitable and reversible materials.The appropriate auxiliary support method shall be selected according to the speci c situation.Based on the stacking of various materials on the city wall, you can clean up the stacked materials, arrange simple protective measures around the city wall, and educate the surrounding residents about the damage of the castle by stacking different things.The city walls in a certain area are mostly adobe and covered with bricks.The bricks behind the city have been removed, revealing a large number of broken earth walls.Under the in uence of rain and other natural environments, many walls are vulnerable to vibration, which brings hidden dangers to production safety and the life safety of surrounding residents, so it needs to be properly handled, such as outsourcing support.

α 2 Take
TemperatureHeatMap as an example.In the drawing process, the temperature value as Double is rst normalized by the following formula, so that all points fall within the range of [0,1].12 According to the normalized values obtained, they can be further converted into color values that can represent their features.In this experiment, RGB color mode is used for color representation.The color value is divided into three parts: [Blue Green] is used to indicate the low temperature range; [Green yellow] is used to indicate the average temperature range; [Yellow red] is used to indicate the high temperature range.The speci c RGB transformation diagram is shown in Fig. 5:

Figure 5 Schematic 7
Figure 5 This article discusses how to use reduceByKey to merge initial input coordinate points.Here, data volume reduction is performed on all GDELT data sets during operation, as shown in Table1: ′