A pnt trustworthiness system design and metric method

Abstract

The application discloses a PNT credibility system design and measurement method, comprising a credibility system architecture model design and a corresponding credibility measurement method; the credibility system architecture model comprises a system three-dimensional architecture model and an engineering architecture model; the system three-dimensional architecture model is composed of a cubic factor and an outer contour factor; the cubic factor is composed of three dimensions of a hierarchical factor, a navigation source factor and an influence factor; the outer contour factor covers the cubic factor; specifically, the outer contour factor refers to guaranteeing credibility technology through traceability; the engineering architecture model reflects the collaborative work between heterogeneous navigation sources under the PNT credibility system, and the contribution of each navigation source and related technology in the credibility system; finally, a set of credibility measurement methods corresponding to the credibility system architecture model is provided; the traceability system of the application takes decentralization as the core, and can help to determine the cause of the untrustworthiness of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of positioning, in particular to a PNT credibility system design and measurement method. BACKGROUND

[0002] The application of location-based services makes the positioning technology receive more and more attention, and higher requirements are put forward for the accuracy of the positioning result. At present, the positioning, navigation and timing (PNT) system based on networked space-time resource unified management and cloud collaborative monitoring processing, with all-in-one, accurate, unified, integrated and intelligent space-ground fusion of more systems or navigation sources, provides all-weather, all-time PVT (position, velocity and time) information for global users. Due to the fact that radio signals are vulnerable to unintentional interference from radio transmitters, mobile communication networks and other non-intentional interference, as well as intentional interference and deception of radio signals in the same frequency band, the credibility of the information is unknown during use, which increases the difficulty of credibility evaluation of positioning. At present, there is no reasonable solution. SUMMARY

[0003] To solve the above technical problems, the present application provides a PNT credibility system design and measurement method, which comprises designing a credibility system architecture model and a corresponding credibility measurement method; the credibility system architecture model comprises a system three-dimensional architecture model and an engineering architecture model, the system three-dimensional architecture model is composed of a cubic factor and an outer contour factor, the cubic factor is composed of three dimensions of hierarchical structure, heterogeneous navigation source mode providing information and factors affecting credibility, and the outer contour factor covers three-dimensional factors, specifically, it refers to guaranteeing credibility through traceability; the engineering architecture model embodies the collaborative work between heterogeneous navigation sources in the PNT system, and the contribution of each navigation source and related technology in the whole system, and provides a credibility measurement method based on the credibility system architecture model.

[0004] To achieve the above purpose, the present application adopts the following technical solutions:

[0005] A PNT credibility system design and measurement method, comprising the following steps:

[0006] Step 1, designing a PNT credibility system architecture model;

[0007] Step 2, according to the trustworthiness system architecture model designed in step 1, the trustworthiness is measured.

[0008] Further, in step 1, the trustworthiness system architecture model includes a system stereoscopic architecture model and an engineering architecture model; the system stereoscopic architecture model is composed of a cube factor and an external contour factor; the cube factor is composed of three dimensions of hierarchical structure, heterogeneous navigation source mode of providing information, and factors affecting trustworthiness; the external contour factor covers three-dimensional factors, that is, ensuring trustworthiness through traceability; the engineering architecture model embodies the cooperation between heterogeneous navigation sources and the contribution of each navigation source in the whole system.

[0009] Further, in step 1, the trustworthiness of the PNT system is the ability of the PNT system to continuously and stably provide original data for solving PVT information to users within a specified time, including the ability of the whole information chain from the receiving end to the signal end without tampering, anti-interference and deception, the ability of mutual verification of all signal source information in the PNT system, the ability of system trustworthiness evaluation, and the ability of tracking, countermeasures and information recovery of attack sources; the trustworthiness of PNT improves the security of PNT service, including physical security and logical security; wherein, the physical security means that each system, terminal device and related infrastructure is physically protected from malicious damage; the logical security means the trustworthiness of information in PNT service.

[0010] Further, in step 1, the cube factor is composed of three dimensions of "horizontal, vertical and deep", the "horizontal" of the cube refers to the hierarchical structure of PNT, the "vertical" of the cube refers to the heterogeneous navigation source in PNT that can provide information, and the "deep" of the cube refers to the factors in PNT that can affect its trustworthiness.

[0011] Further, in step 1, the hierarchical structure of PNT is composed of a physical layer, a transmission layer and a service layer, the physical layer includes all hardware infrastructure settings, its task is to define the standards of each device and provide trustworthiness guarantee of the source end; the transmission layer includes a series of transmission protocols and a series of inherent error elimination methods, which provides trustworthiness guarantee of the transmission link; the service layer faces the user terminal and provides trustworthiness service for the user terminal, formulates technologies and methods including trustworthiness authentication technology, trustworthiness monitoring technology of satellite-ground enhancement system, and user terminal autonomous trustworthiness monitoring technology, to guarantee the trustworthiness of service; the hierarchical structure of PNT also includes the protocol and data link of information transmission, and the authentication, monitoring means and methods for improving the performance of PNT service.

[0012] Further, in step 1, the heterogeneous navigation source mode provides navigation information provided by the heterogeneous navigation source in three categories: first, navigation sources providing global navigation information; second, navigation sources providing enhanced information; third, navigation sources providing local navigation information; the user terminal is equipped with a component that can receive global navigation information; factors that can affect its credibility include device aging, device damage, message tampering, interference, deception, obstruction, terminal jolting, weather, light, and particle concentration; for different influencing factors, protection or correction is carried out through encryption, mutual verification, and backup means to ensure the credibility of PNT.

[0013] Further, in step 1, the PNT credibility system three-dimensional architecture model obtains three orthogonal credibility space representation models through projection, including a credibility space representation model with navigation sources and hierarchical structure as retrieval conditions, which represents the credibility of different navigation sources under different hierarchical structures; a credibility space representation model with navigation sources and influencing factors as retrieval conditions, which represents the credibility of different navigation sources under different influencing factors; and a credibility space representation model with influencing factors and hierarchical structure as retrieval conditions, which represents the credibility of different influencing factors under different hierarchical structures.

[0014] Further, step 2 includes single evaluation first and overall optimization, with each link's fuzzy variable forming a credibility space containing credibility, and multiple fuzzy variables forming a multi-element credibility space representing the credibility of the entire PNT system; at the same time, the decentralized credibility system evaluates a single target based on multi-node data, with the multi-information filtering result as the final overall credibility index.

[0015] Further, in step 2, a global credibility model is established based on the credibility system architecture, local credibility model, and fuzzy comprehensive evaluation method, and the credibility evaluation means obtained by any model is independent of the other two models working alone, while the credibility evaluation results obtained by the three models complement and verify each other; the design of the local credibility model includes the following steps:

[0016] Step 1, define relative positioning accuracy , relative deterioration accuracy , and credibility ; assume that the initial source is a position result provided by a navigation source without any measures, the relative positioning accuracy of the initial source is 1, the relative deterioration degree is 1, and the relative credibility is 0; the relative positioning accuracy , representing the positioning accuracy of the user terminal relative to the initial source, the lower the relative positioning accuracy of the navigation source, the higher the relative positioning accuracy of the navigation source. Set the positioning accuracy of the initial source as Then the relative positioning accuracy of the user terminal for:

[0017] (1)

[0018] Step 2: Calculate the relative degradation accuracy. The output represents the difference between the user's input and output before and after the user encounters unreliable factors. The relative degree of deterioration in positioning accuracy. The larger the value, the greater the degradation in relative positioning accuracy; The smaller the value, the lower the degree of degradation in relative positioning accuracy; after encountering unreliable factors, the user's output... Positioning accuracy is denoted as The initial source output Positioning accuracy is denoted as This relatively worsens the accuracy. for:

[0019] (2)

[0020] Step 3: Calculate credibility This characterizes the user's ability to resist untrustworthy factors; The smaller the value, the lower the credibility. The larger the value, the higher the credibility, and thus the higher the credibility of the user terminal relative to the initial source. Characterized as:

[0021] (3).

[0022] Furthermore, in step 2, the relationship between the global credibility model and the local credibility model is established using the fuzzy comprehensive evaluation method, including the following steps:

[0023] Step (1) The elements in the server-signal source model represent the service methods of different signal sources at different physical layers. The elements in the server-signal source model are all factors that affect the reliability of the system. The factors are unrelated and are denoted as follows: ;

[0024] Step (2) takes into account that different users have different needs for credibility, therefore, the weight allocation among the factors is set according to different needs, which is as follows: A fuzzy vector on, denoted as ,in, For the first The weights of each factor, and satisfying If the sum is not equal to 1, then normalization is performed here, or normalization is performed at the final result.

[0025] Step (3) Establish elements based on the local trust model Regarding the probability of credibility Evaluation vector Assume that the elements are obtained through a local trust model. The credibility is The variance is ,but , and satisfy , When different calculation methods result in different evaluation vectors At the same time, the overall evaluation matrix A multi-center, equally weighted overall evaluation matrix was obtained. The final overall evaluation matrix ;

[0026] Obtain evaluation results This vector represents the system's credibility. The probability of this is ; with Corresponding confidence probability As a measure of the system's credibility.

[0027] Beneficial effects:

[0028] This invention elucidates the trustworthiness of PNT from both system architecture and engineering architecture perspectives, analyzing it from theoretical and engineering practice angles to illustrate the inherent connections between various components in maintaining the trustworthiness of the PNT system. Specifically, a three-dimensional architecture model is established in the system architecture, abstracting the system into three orthogonal dimensions: hierarchical structure, heterogeneous navigation sources, and influencing factors. Subsequently, the trustworthiness analysis planes formed by each of these three dimensions are analyzed pairwise, specifically describing the analysis of another dimension in different trustworthiness analysis planes, the trustworthiness enhancement development path for that other dimension, and its connection to current work. This invention aims to pinpoint existing shortcomings in trustworthiness development through system architecture and propose theoretical directions for future development. Conversely, the engineering architecture describes the collaborative work between heterogeneous navigation sources within the PNT system, as well as the contributions of each navigation source and technology to the entire PNT system. Furthermore, it emphasizes the traceability of ensuring PNT trustworthiness; a decentralized traceability system can help identify the causes of system untrustworthiness. Attached Figure Description

[0029] Figure 1 A schematic diagram of the three-dimensional architecture model of the PNT trustworthiness system;

[0030] Figure 2 This is a schematic diagram of the hierarchical structure of PNT;

[0031] Figure 3 This is a schematic diagram of the engineering architecture model. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0033] The present application discloses a PNT credibility system design and measurement method, comprising the following steps:

[0034] Step 1, design a PNT credibility system architecture model;

[0035] Step 2, according to the credibility system architecture model designed in step 1, perform credibility measurement.

[0036] The credibility system architecture model includes a system stereoscopic architecture model and an engineering architecture model. The system stereoscopic architecture model is composed of a cube factor and an outer contour factor. The cube factor is composed of three dimensions of hierarchical structure, heterogeneous navigation source mode of providing information and factors affecting credibility; the outer contour factor covers three-dimensional factors, specifically, it refers to ensuring credibility through traceability; the engineering architecture model embodies the collaborative work between heterogeneous navigation sources under the PNT system, and the contribution of each navigation source and related technology in the whole system.

[0037] The credibility of the PNT system is the ability of the PNT system to continuously and stably provide original data for solving PVT information to users within a specified time. That is, the research scope of the credibility of PNT covers all factors affecting the user's timely access to accurate PVT information caused by the error source information correction part of the non-PNT system signal source. Specifically, the credibility system of PNT should include but is not limited to the tamper-proofing, anti-interference deception ability of the whole information chain from the data receiving end to the signal end information transmission, the mutual verification ability of all signal source information in the PNT system, the system credibility evaluation ability and the tracking, countermeasures and information recovery ability of the attack source.

[0038] As Figure 1As shown, the generation of PVT information needs to go through three processes of generation, propagation and reception. In these three processes, any process that produces untrusted factors will affect the security of the system. The trustworthiness of PNT needs to take different measures and means for signals and information in PNT in these three processes, and conduct all-round trust enhancement. Therefore, according to the different directions and different levels of content covered by PNT trustworthiness, the PNT trustworthiness system architecture model is designed from the perspective of multi-dimensional and multi-level. Based on this, the three-dimensional architecture model of PNT trustworthiness system is composed of cube factor and outer contour factor. Among them, the cube factor is composed of three dimensions of "horizontal, vertical and deep". The "horizontal" of the cube refers to the hierarchical structure of PNT, the "vertical" of the cube refers to the heterogeneous navigation source in PNT that can provide information, and the "deep" of the cube refers to the factors that can affect the trustworthiness of PNT. The outer contour factor covers the three-dimensional factor, and the evaluation of the trustworthiness of PNT needs to consider the cube factor and the outer contour factor comprehensively.

[0039] The hierarchical structure of PNT refers to the existing Internet architecture and wireless network 802.11 standard

[31] , and according to the composition architecture of PNT and its inherent properties, it is divided into a three-layer architecture model composed of "physical layer, transmission layer and service layer", as shown in Figure 2 The physical layer contains all the hardware infrastructure settings under the system, its task is to define the standards of each device, such as interface standards and types, carrier signal power, transmission rate, frequency band, etc., to provide trusted security for the source; the transmission layer includes a series of transmission protocols and a series of inherent error elimination methods, such as ionospheric error, tropospheric error, multipath effect elimination method, to provide trusted security for the transmission link; the service layer faces the user terminal, provides trusted services for the user terminal, and formulates technologies and methods including trusted authentication technology, trusted monitoring technology of satellite-ground enhancement system, and user terminal autonomous trusted monitoring technology, to guarantee the trustworthiness of the service. In the hierarchical structure of PNT trustworthiness, in addition to a large number of signal sources, it also includes protocols and data links of navigation messages, communication protocols and other information transmission, as well as authentication, monitoring and other technical means and methods to improve the performance of PNT service. The trustworthiness of PNT improves the security of PNT service, including physical security and logical security. Among them, the physical security refers to the physical protection of each system, terminal device and related infrastructure, to prevent malicious damage, etc.; the logical security refers to the trustworthiness of information in PNT service. In the three-layer model, the service layer faces the user terminal, and the purpose is to guarantee the trustworthiness of the service.

[0040] The navigation information provided by the heterogeneous navigation sources is divided into three categories: first, navigation sources that can provide global navigation information, such as GPS, Beidou, etc.; second, navigation sources that can provide enhanced information, such as pseudolites, etc.; and third, navigation sources that can provide local navigation information, such as INS, visual odometry, wheel odometry, lidar, etc. User terminals usually carry components that can receive global navigation information, such as GPS receivers or 5G chips. The working mechanisms of various navigation sources are different, showing obvious heterogeneous characteristics, but these heterogeneous navigation sources are different from GNSS in that they are not interfered by radio signals and can provide auxiliary PVT information. Factors that can affect its credibility include, but are not limited to, device aging, device damage, message tampering, interference, deception, obstruction, terminal jolting, weather, light, particle concentration, etc. For different influencing factors, encryption, mutual verification, backup, etc. means are usually needed to protect or correct in order to ensure the credibility of PNT. The traceability is achieved through a combination of software and hardware, through existing base stations to form a multi-centralized backup platform that can backup all data generated during navigation. The backup of all data generated during navigation can be used as an important representation method for system credibility evaluation.

[0041] The PNT credibility system stereoscopic architecture model can obtain three orthogonal credibility space representation models through projection. Specifically, it includes a credibility space representation model with navigation sources and hierarchical structure as retrieval conditions. This model element represents the credibility of different navigation sources under different hierarchical structures. A credibility space representation model with navigation sources and influencing factors as retrieval conditions. This model element represents the credibility of different navigation sources under different influencing factors. A credibility space representation model with influencing factors and hierarchical structure as retrieval conditions. This model element represents the credibility of different influencing factors under different hierarchical structures. Specifically as shown in Table 1, Table 2, and Table 3:

[0042] (1) Influence factor: The influence factor represents the influence size of the PNT influencing factor exhibited by different heterogeneous navigation sources in different levels.

[0043] Table 1

[0044]

[0045] (2) Navigation source factor: The navigation source factor represents which navigation sources are affected by different influences in different levels.

[0046] Table 2

[0047]

[0048] (3) Hierarchy factor: The hierarchy factor represents different navigation sources, and through different services or attack means, which layers are attacked / reacted.

[0049] Table 3

[0050]

[0051] As Figure 3 shown, the engineering architecture model explains the working mechanism of PNT credibility from the perspective of engineering implementation. Specifically, taking GNSS, SBAS, and 5G as the core, a global PVT center can be obtained, which needs to be self-verified internally to evaluate its credibility, while cooperating with airborne sensors such as INS, WIFI, and ODOM, etc. to realize the credibility detection between navigation sources. Meanwhile, the two complement each other, suppress the influence of noise through the characteristics of noise space orthogonality, and then through blockchain and 5G technology, realize the traceability of information, the tracking, countermeasures, and information recovery ability of attack sources.

[0052] Based on the above PNT credibility system architecture model, the corresponding credibility measurement method adopts the idea of first single evaluation and then overall optimization. Obviously, each link can be approximated as a fuzzy variable in the whole credibility system, which is subject to credibility theory, and its credibility function satisfies the credibility measure. Therefore, for each fuzzy variable in each link, a credibility space containing credibility can be constructed, and the multi-dimensional credibility space composed of multiple fuzzy variables collectively represents the credibility degree of the whole PNT system. At the same time, the decentralized credibility system can evaluate a single target based on multi-node data, and use the multi-information filtering result as the final overall credibility index.

[0053] Considering that different types of sensors have different system architectures and are subject to different spoofing means, the means to improve the feasibility are also different, so it is difficult to give a complete mathematical description of a local credibility model. Therefore, relying on its physical and mathematical characteristics, the existing research foundation is followed to give the credibility of each stage. In addition, for those who cannot give accurate credibility results, a local credibility model is given. Specifically, the local credibility model includes the following steps:

[0054] Step 1, define the relative positioning accuracy , the relative dilution of precision and the credibility . Assuming that the initial source is a navigation source without any measures to provide a position result, the relative positioning accuracy of the initial source is 1, the relative dilution of precision is 1, and the relative credibility is 0. The relative positioning accuracy , the smaller the relative positioning accuracy of the user end relative to the initial source, , the lower the relative positioning accuracy of the navigation source. The larger, the higher the relative positioning accuracy of the navigation source is. Assuming that the positioning accuracy of the initial source is , the relative positioning accuracy of the user end is :

[0055] (1)

[0056] Step 2, the relative deterioration accuracy is calculated, and the relative deterioration accuracy represents the relative deterioration degree of the output positioning accuracy of the user end before and after the user end suffers from the untrusted factor, the larger, the higher the deterioration degree of the relative positioning accuracy is; the smaller, the lower the deterioration degree of the relative positioning accuracy is. After suffering from the untrusted factor, the output positioning accuracy of the user end is denoted as , the output positioning accuracy of the initial source is denoted as , and the relative deterioration accuracy is:

[0057] (2)

[0058] Step 3, the trustworthiness represents the resistance ability of the user end to the untrusted factor. the smaller, the lower the trustworthiness is; the larger, the higher the trustworthiness is, and the trustworthiness of the user end relative to the initial source can be represented as:

[0059] (3)

[0060] The establishment of the global trust mode relies on the trustworthiness system architecture, the local trust model and the fuzzy comprehensive evaluation method. According to the model structure, the three models can be used as trustworthiness analysis means to establish the global trust model. Meanwhile, considering that the three models are orthogonal, the trustworthiness evaluation means obtained by any model can work independently of the other two models, and the trustworthiness evaluation results obtained by the three models can complement and check each other.

[0061] Without loss of generality, the server-signal source model is taken as an example for detailed description. The local trust model describes the trustworthiness of different elements in the measurement model. The trustworthiness of the whole model is measured by introducing the concept of part of fuzzy mathematics, that is, the relationship between the global trust model and the local trust model is established by the fuzzy comprehensive evaluation method. Specifically, the following steps are included:

[0062] ​​​Step (1) The elements in the server-signal source model represent the service methods of different signal sources at different physical layers. All elements in the server-signal source model are factors affecting system reliability. It can be seen that these factors are unrelated, denoted as... .

[0063] Step (2) Considering that different users have different needs for credibility, it is necessary to set the weight allocation among various factors for different needs. A fuzzy vector on, denoted as .in, For the first The weights of each factor, and satisfying If the summation does not equal 1, normalization can be performed here or at the final result. It's worth noting that weights can be determined using methods such as the Delphi method (expert survey method), weighted average method, and peer evaluation method. Generally, the analytic hierarchy process (AHP) can be used when there is limited data, while the entropy weight method can be used when data is available.

[0064] Step (3) Establish elements based on the local trust model Regarding the probability of credibility Evaluation vector Assume that the elements are obtained through a locally reliable model. The credibility is The variance is ,but , and satisfy , At the same time, it is permissible for different calculation methods to result in different evaluation vectors. Different. Therefore, the overall evaluation matrix... A multi-center approach can yield an equally weighted overall evaluation matrix. The final overall evaluation matrix .

[0065] Obtain evaluation results This vector represents the system's credibility. The probability of this is Generally speaking, with Corresponding confidence probability As a measure of the system's credibility.

[0066] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A PNT trustworthiness system design and metrics method, characterized in that, Comprising the following steps: Step 1, design a PNT credibility system architecture model, the PNT credibility system architecture model comprises a system three-dimensional architecture model and an engineering architecture model; the system three-dimensional architecture model comprises a cubic factor; the cubic factor consists of three dimensions of hierarchical factor, navigation source factor and influence factor; The engineering architecture model embodies the collaborative work between heterogeneous navigation sources and the contribution of each navigation source in the whole credibility system; With GNSS, SBAS, and 5G as the core, a global PVT center is obtained, which internally performs self-checking to evaluate its credibility, and cooperates with airborne sensors to realize credibility detection between navigation sources, while the two complement each other, suppress the influence of noise through the characteristics of noise space orthogonality, and then through blockchain and 5G technology, through decentralization, realize the traceability of information, the tracking, countermeasures and information recovery ability of attack sources; The cubic factor consists of three dimensions of "horizontal, vertical and deep", the "horizontal" of the cube refers to the hierarchical factor, which is the hierarchical structure of PNT, the "vertical" of the cube refers to the navigation source factor, which is the heterogeneous navigation source that can provide information in PNT, and the "deep" of the cube refers to the influence factor, which is the factor that can affect the credibility of PNT; The "horizontal" of the cube includes three hierarchical factors of service layer, transmission layer and physical layer, the "vertical" of the cube includes three types of heterogeneous navigation sources: one is the navigation source that can provide global navigation information, including GPS and Beidou; two is the navigation source that can provide enhanced information, including pseudolite; three is the navigation source that can provide local navigation information, including INS, visual odometry, wheel odometry and laser radar; The "deep" of the cube includes device aging, device damage, tampering, interference, deception, shielding, terminal jolt, light, and particle concentration; The hierarchical factor of PNT consists of physical layer, transmission layer and service layer, the physical layer contains all hardware infrastructure settings, including data standards generated by each navigation source, providing source-side credibility assurance; The transmission layer includes a series of information transmission protocols and data links, improves the authentication, monitoring means and methods of PNT service performance and a series of inherent error elimination methods, and provides credibility assurance for transmission link; The service layer faces the user terminal and provides credible services for the user terminal, including credible authentication technology, credible monitoring technology of satellite-ground enhancement system, and user-end self-reliant credible monitoring technology, to ensure the credibility of the service; Step 2, according to the PNT credibility system architecture model designed in step 1, perform credibility measurement, including first single evaluation and then overall optimization, construct a credibility space containing credibility for each link fuzzy variable, and multiple fuzzy variables constitute a multivariate credibility space to represent the credibility of the whole PNT system; At the same time, the decentralized credibility system evaluates a single target according to multi-node data, and uses multi-information filtering results as the final overall credibility index.

2. The PNT trustworthiness system design and metric method of claim 1, wherein, The trustworthiness of the PNT system in step 1 is the ability of the PNT system to continuously and stably provide data for solving PVT information to the user within a specified time, including the ability of the whole information chain from the receiving end to the signal end to be tamper-free and anti-interference and deception, the ability of all navigation source information in the PNT system to verify each other, the ability of the system to evaluate trustworthiness, and the ability to track, counteract and recover information from attack sources; the trustworthiness of the PNT improves the security of the PNT service, including physical security and logical security; wherein the physical security means that each system, terminal device and related infrastructure is physically protected from malicious damage; the logical security means the trustworthiness of information in the PNT service.

3. The PNT trustworthiness system design and metric method of claim 1, wherein, In step 1, the heterogeneous navigation source mode provides navigation information in three categories: one is a navigation source that provides global navigation information; two is a navigation source that provides enhanced information; and three is a navigation source that provides local navigation information; The user terminal is equipped with a component that can receive navigation information; factors that can affect its trustworthiness include device aging, device damage, message tampering, interference, deception, obstruction, terminal jolt, weather, light, and particle concentration; for different influencing factors, protection or correction is carried out through encryption, mutual verification, and backup means to ensure the trustworthiness of the PNT.

4. The PNT trustworthiness system design and metric method of claim 1, wherein, In step 1, the PNT trustworthiness system three-dimensional architecture model obtains three orthogonal trustworthiness space representation models through projection, including a trustworthiness space representation model with navigation sources and hierarchical structures as retrieval conditions, which represents the trustworthiness of different navigation sources under different hierarchical structures; a trustworthiness space representation model with navigation sources and influencing factors as retrieval conditions, which represents the trustworthiness of different navigation sources under different influencing factors; and a trustworthiness space representation model with influencing factors and hierarchical structures as retrieval conditions, which represents the trustworthiness of different influencing factors under different hierarchical structures.

5. The PNT trustworthiness system design and metric method of claim 4, wherein, In step 2, a global trust model is established according to the trustworthiness system architecture, the local trust model and the fuzzy comprehensive evaluation method; the trustworthiness evaluation means obtained by any model is independent of the other two models and works alone, while the trustworthiness evaluation results obtained by the three models complement and verify each other; the design of the local trust model includes the following steps: Step 1, defining relative positioning accuracy , relative deterioration accuracy and credibility ; assuming that the initial source is a position result provided by a navigation source without any measures, the relative positioning accuracy of the initial source is 1, the relative deterioration degree is 1, and the relative credibility is 0; the relative positioning accuracy , representing the positioning accuracy of the user terminal relative to the initial source, the smaller, the lower the relative positioning accuracy of the navigation source; the greater, the higher the relative positioning accuracy of the navigation source; assuming that the positioning accuracy of the initial source is , then the relative positioning accuracy of the user terminal is: （1） Step 2, calculate the relative deterioration accuracy, the relative deterioration accuracy the output of the user terminal before and after being subjected to the untrusted factor the relative deterioration degree of the positioning accuracy, the greater, the higher the deterioration degree of the relative positioning accuracy; the smaller, the lower the deterioration degree of the relative positioning accuracy; the output of the user terminal after being subjected to the untrusted factor the positioning accuracy is recorded as the positioning accuracy output by the initial source is recorded as the positioning accuracy is recorded as the relative deterioration accuracy is: （2） Step 3, calculating trustworthiness characterizing the user's ability to resist the untrustworthy factor; The smaller, the lower the trustworthiness; The greater, the higher the trustworthiness, then the user's trustworthiness relative to the initial source characterized as: （3）。

Images