Method and system for transmitting a global height reference using an unloaded time-frequency signal

Abstract

The application discloses a method and system for transmitting a unified global height datum by using an empty carrier time-frequency signal, and the method comprises the following steps: obtaining time-frequency observation values based on the empty carrier time-frequency signal transmission; calculating the gravity potential difference of two ground stations based on the transmitted time-frequency observation values; obtaining the altitude of a to-be-measured ground station on a regional geoid according to a conversion model of the gravity potential difference and the altitude; and converting the altitude on the regional geoid to a global unified height datum surface according to a height conversion relationship between the regional geoid and the global unified height datum surface. The application can overcome the defects of high cost, low efficiency and poor precision of traditional altitude measurement, realize cross-sea height measurement, realize the unification of the global height datum in a centimeter level precision, and combine the unification principle of the height datum with the time-frequency transmission technology, thereby providing a new research method for realizing the unification of the global height datum.

Description

Technical Field

[0001] This invention belongs to the fields of geodesy, geophysics and time and frequency science, and specifically relates to a method for high-precision time and frequency transmission of a unified global elevation benchmark, specifically a method and system for transmitting a unified global elevation benchmark using airborne time and frequency signals. Background Technology

[0002] The elevation of a ground point is essential vertical spatial location information for all geographic information products and engineering construction. Its reference surface is the geoid. The determination of elevation and the unification of the global elevation datum are closely related to the gravity field; that is, the elevation of a ground point can be determined by measuring the gravity potential difference between a ground point and a reference point on the mean sea level. The International Union of Geodesy (IUGS) has made achieving high-precision determination of the global geoid and unification of the global elevation datum a strategic goal of geodesy in this century. To this end, many scholars at home and abroad have been committed to researching the unification of the global elevation datum and improving the accuracy of geoid determination by combining various technologies. Currently, traditional methods for determining gravity potential and elevation are time-consuming and labor-intensive. As the survey line grows, the cumulative error increases, making surveys difficult in mountainous areas and other regions with large gravity variations. Furthermore, achieving a unified global elevation datum is challenging because the mean sea level is not the gravity potential equipotential surface (geoid), and gravity potential differences exist between transoceanic countries or regions, making transoceanic joint surveys difficult to conduct using traditional methods. High-precision gravity field models only have a 5′×5′ resolution, providing mean values ​​rather than specific point values. While satellite gravity detection technology can reconstruct a relatively accurate global gravity potential field, its resolution is generally low (approximately 1°×1°). Therefore, to address these challenges, the method of using high-precision airborne time-frequency signals to transmit a unified global elevation benchmark has been extensively studied, providing geodesists with a completely new research approach.

[0003] The time-frequency transfer standard for a unified global elevation benchmark is a practical application of the principles of general relativity. It primarily involves comparing time-frequency signals emitted by a local high-precision optical clock and a remote optical clock to measure gravitational potential. Then, using a conversion model between gravitational potential and altitude, the final altitude is determined. For a long time, the accuracy of atomic clocks has limited the technology for measuring gravitational potential and altitude through time-frequency transfer, hindering its practical application. In recent years, with the maturation of clock manufacturing processes, clocks with an accuracy of 10⁻⁶ have been successfully developed internationally. -19 Clocks of this magnitude, including portable optical clocks, also achieve an accuracy of 10. -18This scale provides the hardware support for unifying the global elevation datum using time-frequency comparison. When using time-frequency signal transmission to implement global elevation datum unification, it is first necessary to use high-precision time-frequency transmission technology to determine the gravity potential of ground stations. Then, the relationship between gravity potential and altitude is studied to achieve the conversion between gravity potential and altitude across the entire region. Finally, the relationship between the regional geoid and the globally unified geoid is studied to achieve the conversion between different geoids and the unification of the global elevation datum. Therefore, how to perform high-precision gravity potential and altitude conversion, and achieve mutual conversion between different elevation systems and the unification of the global elevation datum, has become an urgent problem to be solved. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a method and system for transmitting a unified global elevation benchmark using unloaded time-frequency signals, utilizing an accuracy better than 10... -18 Using optical clocks of this magnitude as measuring devices, high-precision time-frequency comparisons are performed between optical clocks on the ground and on space carriers (satellites or space stations) via space time-frequency links. This allows for the accurate extraction of gravity potential frequency shift signals and the determination of gravity potential differences between ground stations. Furthermore, by utilizing a conversion model between gravity potential differences and altitude, the conversion between gravity potential differences and altitudes can be achieved. Additionally, by exploring the conversion relationships between different elevation benchmarks, the conversion between elevation benchmarks can be realized, ultimately achieving the research goal of unifying elevation benchmarks.

[0005] According to one aspect of the present invention, a method for transmitting a unified global elevation datum using an unloaded time-frequency signal is provided, comprising:

[0006] Obtain time-frequency observations based on unloaded time-frequency signal transmission;

[0007] The gravity potential difference between the two ground stations is calculated based on the transmitted time-frequency observations.

[0008] Based on the conversion model of gravity difference and altitude, the altitude of the ground station to be measured on the regional geoid is obtained;

[0009] Based on the elevation transformation relationship between the regional geoid and the globally unified elevation datum, the elevation on the regional geoid is transformed to the globally unified elevation datum.

[0010] As a further technical solution, the method also includes:

[0011] High-precision optical clocks are installed on both the space station and the ground station to provide time and frequency references;

[0012] The space station and the ground station are connected by a space time-frequency transmission link for time-frequency comparison of optical clocks.

[0013] As a further technical solution, the gravity potential difference between two ground stations is calculated based on the transmitted time and frequency observations, including: using the observations of high-precision optical clocks of the space station and the ground station to perform air-to-ground optical clock time and frequency comparison to obtain the gravity potential of any ground station; and obtaining the gravity potential difference between the two based on the known gravity potential of the ground station and the ground station to be measured.

[0014] As a further technical solution, the gravity potential difference between two ground stations is calculated based on the transmitted time and frequency observations, including: using the observations of high-precision optical clocks of the space station and the ground station to perform a ground-to-space-to-ground optical clock time and frequency comparison to obtain the gravity potential difference between the known ground station and the ground station to be measured.

[0015] As a further technical solution, the conversion model between gravity difference and altitude is as follows:

[0016]

[0017] Wherein, ΔW PQ H represents the gravitational potential difference between the two locations. P This indicates that the altitude of ground station P is known to be high. This represents the average gravity value of the ground station Q to be measured. Let P represent the average gravity value of a known ground station, and R represent the Earth's radius.

[0018] As a further technical solution, when the ground station P is known to be located on the geoid, the elevation of any point i to be measured is:

[0019]

[0020] Among them, C i Let i be the number of Earth positions at point i. Let be the average gravitational force at point i.

[0021] As a further technical solution, the elevation transformation relationship between the regional geoid and the globally unified elevation datum is as follows:

[0022]

[0023] in, W0 represents the gravity potential of the regional geoid, while W0 represents the gravity potential of the globally unified elevation datum. This represents the average gravity from the geoid at point P to the global geoid. H indicates that the elevation of the ground station P to be measured is high on the regional geoid. P This indicates the altitude of the ground station P to be measured on the globally unified elevation datum.

[0024] According to one aspect of the present invention, a system for transmitting a unified global elevation datum using an unloaded time-frequency signal is provided, comprising:

[0025] The first main module is used to acquire time-frequency observations based on the transmission of idle time-frequency signals;

[0026] The second main module is used to calculate the gravity potential difference between the two ground stations based on the transmitted time-frequency observations;

[0027] The third main module is used to obtain the elevation of the ground station under test on the regional geoid based on the conversion model of gravity difference and elevation.

[0028] The fourth main module is used to convert the elevation on the regional geoid to the globally unified elevation datum based on the elevation conversion relationship between the regional geoid and the globally unified elevation datum.

[0029] According to one aspect of the present invention, a ground station device is provided, including a high-precision clock, a memory, and a processor. The high-precision clock is used to provide a frequency reference and a time reference for the ground station. The memory is used to store a computer program. When the processor runs the computer program stored in the memory, the processor executes the method for transmitting a unified global elevation benchmark using an idle time-frequency signal.

[0030] According to one aspect of the present invention, a non-transitory computer read storage medium is provided, the non-transitory computer read storage medium storing computer instructions that cause the computer to execute the method of transmitting a unified global elevation datum using idle time-frequency signals.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] (1) This invention proposes a method for transmitting a unified global elevation benchmark using high-precision airborne time and frequency signals. By using a high-precision satellite (space)-borne optical clock and comparing high-precision time and frequency signals, it is possible to achieve cross-sea elevation measurement and measurement of gravity difference between two locations.

[0033] (2) The high-order model for the conversion of gravity potential difference and altitude proposed in this invention can significantly improve the conversion accuracy of gravity potential difference and altitude in high-altitude areas with significant elevation differences.

[0034] (3) By establishing a conversion model between regional geoid and globally unified geoid, this invention can realize the conversion between different elevation datums and ultimately achieve the research goal of global elevation datum unification. It provides a new approach to achieving global elevation datum unification with centimeter-level accuracy and can provide technical support and innovative solutions for future gravity potential measurement and elevation datum unification. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the method for transmitting a unified global elevation benchmark using unloaded time-frequency signals, provided in an embodiment of the present invention.

[0037] Figure 2 This is a schematic diagram illustrating the principle of determining gravity potential and altitude using time-frequency comparison with an empty optical clock, as provided in an embodiment of the present invention.

[0038] Figure 3 This is a schematic diagram illustrating the principle of measuring gravity potential and altitude between ground stations across the sea and unifying global elevation benchmarks via satellite, as provided in an embodiment of the present invention.

[0039] Figure 4 This is a schematic diagram of the structure of a system for transmitting a unified global elevation benchmark using unloaded time-frequency signals, as provided in an embodiment of the present invention. Detailed Implementation

[0040] The time-frequency transfer standard for a unified global elevation benchmark is a practical application of the principles of general relativity. It primarily involves comparing time-frequency signals emitted by a local high-precision optical clock and a remote optical clock to measure gravitational potential. Then, using a conversion model between gravitational potential and altitude, the final altitude is determined. For a long time, the accuracy of atomic clocks has limited the technology for measuring gravitational potential and altitude through time-frequency transfer, hindering its practical application. In recent years, with the maturation of clock manufacturing processes, clocks with an accuracy of 10⁻⁶ have been successfully developed internationally. -19 Clocks of this magnitude, including portable optical clocks, also achieve an accuracy of 10. -18 This scale provides the hardware support for unifying the global elevation datum using time-frequency comparison. When using time-frequency signal transmission to implement global elevation datum unification, it is first necessary to use high-precision time-frequency transmission technology to determine the gravity potential of ground stations. Then, the relationship between gravity potential and altitude is studied to achieve the conversion between gravity potential and altitude across the entire region. Finally, the relationship between the regional geoid and the globally unified geoid is studied to achieve the conversion between different geoids and the unification of the global elevation datum. Therefore, how to perform high-precision gravity potential and altitude conversion, and achieve mutual conversion between different elevation systems and the unification of the global elevation datum, has become an urgent problem to be solved.

[0041] Using an airborne carrier equipped with a high-precision optical clock as a medium to transmit gravitational potential and altitude between two points on the ground through time and frequency comparison has become a research hotspot for scholars both domestically and internationally. Time-frequency comparison using a spaceborne clock requires a microwave or laser link to connect the clocks at two locations. This method can directly measure the gravitational potential difference between the two locations, avoiding the error accumulation during the measurement process of traditional methods. This method requires both the atomic clock in the air and the atomic clock at the ground station to have an accuracy of 10⁻⁶. -18 The accuracy of the time-frequency link is on the order of magnitude, and its propagation precision reaches that of an atomic clock. Furthermore, achieving global elevation datum unification with centimeter-level accuracy requires constructing a gravity potential and elevation conversion model applicable to all terrains. Therefore, accurately measuring gravity potential and converting it to elevation has become crucial for global elevation datum unification.

[0042] The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that includes a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical features of the various embodiments or individual embodiments provided by the present invention can be arbitrarily combined to form new technical solutions. Such combinations are not bound by the order of steps and / or structural composition patterns, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0044] This invention provides a method for transmitting a unified global elevation benchmark using unloaded time-frequency signals, such as... Figure 1 As shown, the process includes: acquiring time-frequency observations based on the transmission of unloaded time-frequency signals; calculating the gravity difference between two ground stations based on the transmitted time-frequency observations; obtaining the elevation of the ground station under test on the regional geoid according to the conversion model between gravity difference and elevation; and converting the elevation on the regional geoid to the global unified elevation datum according to the elevation conversion relationship between the regional geoid and the global unified elevation datum.

[0045] In this embodiment of the invention, two ground stations are set up arbitrarily across the sea or continent, and the elevation of each station relative to the local reference geoid is a known value. A time-frequency satellite or space station is used to connect the two points, and high-precision time-frequency transfer data acquisition for gravity potential measurement is performed, collecting time-frequency comparison data.

[0046] like Figure 2 As shown in the diagram, A represents a space station or satellite, B represents any ground point, C represents a point on the quasi-geoid, D represents a point on the geoid, and E represents a point on a reference ellipsoid. By measuring the gravity potential of any station using a satellite or space station, and then comparing it with a clock on any reference surface, the elevation of any station relative to the reference surface can be obtained. Through the conversion relationships between different reference surfaces or elevation systems, elevation conversion between different elevation systems and between reference surfaces is achieved, ultimately realizing a unified elevation datum.

[0047] To achieve the application objectives, this embodiment of the invention uses a high-precision time-frequency transfer method to measure gravity potential and altitude, and performs ground-to-satellite (space-to-ground) time-frequency transfer. The observed values ​​are calculated to obtain the altitude of the ground station relative to the local elevation datum. Then, using the conversion relationship between the regional geoid and the globally unified geoid proposed in this embodiment of the invention, the altitude of the regional geoid is converted to the altitude on the globally unified geoid, thereby achieving global elevation datum unification.

[0048] like Figure 3 As shown in the figure, S represents the Chinese space station or satellite, and P and Q represent two ground stations across the sea, connected by a satellite or space station. When the two ground stations can simultaneously observe the same time-frequency satellite, the gravity potential difference between points P and Q is obtained by differentiating the time-frequency signals of the two stations. Then, the conversion model mentioned in this embodiment of the invention is used to convert the gravity potential to altitude. By utilizing the relationship between the local geoid referenced at P and Q and the globally unified geoid, the reference surface is converted, ultimately achieving the unification of the elevation datum between the two locations across the sea.

[0049] In this embodiment of the invention, the data acquisition process includes the following steps:

[0050] a. Atomic clock setup: The atomic clocks on the ground and in space are high-precision optical clocks with a long-term stability of 10. -18 Magnitude.

[0051] b. Data acquisition: Set up ground stations across the sea or across continents that can simultaneously observe the same time-frequency satellite or space station to continuously acquire and record time-frequency comparison data between the satellite (space) and the ground.

[0052] c. Data download: Utilize broadcast messages transmitted from space carriers to receive data collected by space equipment, and simultaneously download data collected by ground equipment.

[0053] d. Data processing: Using a method that uses high-precision airborne time-frequency signal transmission to unify the global elevation benchmark, the gravity potential and altitude of any two ground stations are calculated, and a unified elevation benchmark conversion is performed. The elevation benchmark can be unified in a small area using the method described in this invention. Then, the elevation is compared with that measured by traditional methods to analyze the accuracy of the method of this invention.

[0054] By utilizing high-precision, unloaded time-frequency signals to transmit a unified global elevation datum, the following results can be obtained:

[0055] (1) Achieve high-precision conversion of gravity position and altitude: It can convert the gravity position and altitude of any ground station with centimeter-level accuracy.

[0056] (2) Achieve global elevation benchmark unification: Achieve elevation measurement at any point without leveling, and solve the problem that traditional elevation measurement is difficult to achieve cross-sea measurement, realize cross-sea and cross-continental elevation transfer, and achieve global elevation benchmark unification at the centimeter level.

[0057] In this embodiment of the invention, the method for transmitting a unified global elevation benchmark using high-precision airborne time-frequency signals further includes the following steps:

[0058] 1) A ground observation station will be established at the target station, equipped with equipment that provides long-term stability better than 10. -18 High-precision optical clocks provide ground stations with high-precision and high-stability frequency and time references. Space carriers (satellites or space stations) equipped with optical clocks of equal precision can perform air-to-ground optical clock time-frequency comparisons, as well as ground-to-air (satellite)-to-ground optical clock time-frequency comparisons (e.g.,...). Figure 2 (As shown). Assume the microwave frequency emitted from point A is f. A The microwave frequency received at point B is f. B Considering the relative frequency deviations of the atomic clocks at points A and B as y, A and y A Therefore, the unidirectional microwave frequency transfer model in free space is:

[0059]

[0060] In the model The Doppler shift is caused by the relative motion between the space station and the ground station. The frequency shift caused by the gravitational potential. and The terms represent the effects of the ionosphere, troposphere, and other hardware on microwave frequencies.

[0061] It should be noted that when performing a direct air-to-ground comparison, the gravitational potential at any ground point can be obtained, and then the gravitational potential difference between two ground stations can be calculated based on the gravitational potential. When using ground-to-air (satellite)-to-ground optical clock time-frequency comparison, the gravitational potential difference between two points on the ground can be obtained.

[0062] 2) According to the definition of gravitational potential, when the gravitational potential at the geoid is W0, the gravitational potential at any point P on the ground (e.g., W0) is W0. Figure 3 The gravitational potential of ) can be expressed as:

[0063]

[0064] In the formula, H P It is the orthogonal elevation at point P (in meters). The gravity at point P on the geoid (unit: m / s²) 2 )), (R is the Earth's radius), Indicates greater than or equal to The term is taken when the ground station is located in a flat area, and when the ground station is located in a mountainous area with rapidly changing terrain, the term is taken.

[0065] Assume points P and Q are ground stations (e.g., ...). Figure 2 As shown), given the gravitational potential at point P, when point Q is located in a mountainous area with significant elevation differences, the second-order term in equation (2) needs to be considered. The elevation at point Q can be expressed as:

[0066]

[0067] Wherein, ΔW PQ It is the gravitational potential difference between the two locations. When point P is located on the geoid, H in equation (3) P =H0, W P =W0, then the elevation at any point i is:

[0068]

[0069] Among them, C i Let i be the number of Earth positions at point i.

[0070] 3) Accurately obtain the gravity potential of the ground station using time-frequency transfer technology, and then calculate the station's position relative to the regional geoid. The area with the highest elevation (H) as the benchmark L The difference between the regional elevation datum and the global elevation datum at any point P is:

[0071]

[0072] in, This is the average gravity of the regional geoid at point P to the global geoid. Therefore, the regional elevation to the global reference elevation is converted as follows:

[0073]

[0074] Equations (5) and (6) can be used to reduce the regional elevation to the globally unified geoid, thereby achieving the unification of the global elevation datum.

[0075] This invention utilizes a high-precision, airborne time-frequency signal transmission method to unify a global elevation benchmark. This method effectively connects two ground points across oceans and continents, enabling the measurement of gravity potential differences between the two locations (or between space / satellite and ground). Through a high-order gravity potential and elevation conversion model, centimeter-level accuracy conversion can be achieved for mountainous regions with significant elevation variations. Furthermore, through a conversion model between regional and globally unified geoids, a unified global elevation benchmark can ultimately be achieved. This method offers advantages such as high precision, high stability, and the ability to operate across oceans, overcoming the shortcomings of traditional gravity potential and elevation measurement methods, such as low efficiency, high cost, and poor accuracy. When the stability of the high-precision atomic clock used for measurement reaches 10... -18 At the order of magnitude, it can meet the centimeter-level accuracy requirement for a unified global elevation benchmark, greatly improving the efficiency of high-altitude measurements and providing a guarantee for geodesy to enter the time-frequency quantum era.

[0076] The method for unifying the global elevation datum using time-frequency transmission proposed in this invention has the following advantages:

[0077] The measuring tool used in this invention has a long-term stability of better than 10. -18 The high-precision optical clock provides a high-frequency reference for the determination of gravitational potential and altitude. The time and frequency comparison of the optical clocks at two locations is achieved through a space time and frequency transmission link. The gravitational potential difference between the two locations is determined through a ground-to-space (satellite)-to-ground time and frequency link. In actual measurements, since the clocks at the two locations are connected through a space time and frequency link, it is possible to transfer elevation data across the sea.

[0078] This invention extends the conversion formula between gravity potential difference and elevation difference to a quadratic term. Compared with the traditional conversion model, it can effectively improve the measurement accuracy of altitude in mountainous areas where elevation difference changes rapidly. It solves the problem of how to achieve high-precision conversion between gravity potential difference and elevation difference between two locations after obtaining high-precision gravity potential difference measurement results using time-frequency transfer technology.

[0079] This invention can directly measure the gravity potential difference between two locations through time-frequency comparison. Then, based on the relationship between different regional elevation benchmarks, it constructs a conversion model between regional elevation benchmarks and a globally unified elevation benchmark, which can realize the conversion between different elevation benchmarks and achieve the unification of elevation benchmarks across seas and continents.

[0080] The implementation of the various embodiments of the present invention is based on programmed processing by a device with processor functionality. Therefore, in practical engineering, the technical solutions and functions of the various embodiments of the present invention are encapsulated into various modules. Based on this reality, and building upon the above embodiments, the embodiments of the present invention provide a system for transmitting a unified global elevation datum using an unloaded time-frequency signal. This system is used to execute the method for transmitting a unified global elevation datum using an unloaded time-frequency signal in the above method embodiments.

[0081] See Figure 4 The system includes: a first main module for acquiring time-frequency observations based on the transmission of unloaded time-frequency signals; a second main module for calculating the gravity potential difference between two ground stations based on the transmitted time-frequency observations; a third main module for obtaining the altitude of the ground station under test on the regional geoid according to the conversion model between gravity potential difference and altitude; and a fourth main module for converting the altitude on the regional geoid to the globally unified elevation datum according to the elevation conversion relationship between the regional geoid and the globally unified elevation datum.

[0082] It should be noted that the system embodiments provided by this invention, in addition to implementing the methods in the above method embodiments, are also used to implement the methods in other method embodiments provided by this invention. The difference lies only in setting corresponding functional modules, and their principles are basically the same as those of the above system embodiments provided by this invention. As long as those skilled in the art, based on the above system embodiments and referring to the specific technical solutions in other method embodiments, obtain corresponding technical means and technical solutions composed of these technical means by combining technical features, and improve the modules in the above system embodiments while ensuring the practicality of the technical solutions, they can obtain corresponding system-like embodiments for implementing the methods in other method-like embodiments. For example:

[0083] Based on the above system embodiments, as a preferred embodiment, the system for transmitting a unified global elevation benchmark using unloaded time-frequency signals provided in this embodiment of the invention, wherein the second main module is further configured to execute the following instructions:

[0084] By using the observations of high-precision optical clocks from the space station and ground station, a time-frequency comparison between the space and ground optical clocks is performed to obtain the gravity potential of any ground station; based on the known gravity potentials of the ground station and the ground station to be measured, the gravity potential difference between the two is obtained.

[0085] Based on the above system embodiments, as a preferred embodiment, the system for transmitting a unified global elevation benchmark using unloaded time-frequency signals provided in this embodiment of the invention, wherein the second main module is further configured to execute the following instructions:

[0086] By using the observations of high-precision optical clocks from the space station and ground station, a time-frequency comparison of the ground-space-ground optical clocks is performed to obtain the gravitational potential difference between the known ground station and the ground station to be measured.

[0087] Based on the above system embodiments, as a preferred embodiment, the system for transmitting a unified global elevation benchmark using unloaded time-frequency signals provided in this embodiment of the invention has the following conversion model for gravity difference and altitude:

[0088]

[0089] Wherein, ΔW PQ H represents the gravitational potential difference between the two locations. P This indicates that the altitude of ground station P is known to be high. This represents the average gravity value of the ground station Q to be measured. Let P represent the average gravity value of a known ground station, and R represent the Earth's radius.

[0090] Based on the above system embodiments, as a preferred embodiment, the system for transmitting a unified global elevation benchmark using unloaded time-frequency signals provided in this embodiment of the invention, when the ground station P is known to be located on the geoid, provides the elevation of any point i to be measured as follows:

[0091]

[0092] Among them, C i Let i be the number of Earth positions at point i. Let be the average gravitational force at point i.

[0093] Based on the above system embodiments, as a preferred embodiment, the system for transmitting a unified global elevation datum using unloaded time-frequency signals provided in this embodiment of the invention has the following elevation conversion relationship between the regional geoid and the globally unified elevation datum:

[0094]

[0095] in, W0 represents the gravity potential of the regional geoid, while W0 represents the gravity potential of the globally unified elevation datum. This represents the average gravity from the geoid at point P to the global geoid. H indicates that the elevation of the ground station P to be measured is high on the regional geoid. P This indicates the altitude of the ground station P to be measured on the globally unified elevation datum.

[0096] This invention also provides a ground station device, including a high-precision clock, a memory, and a processor. The high-precision clock is used to provide frequency and time references for the ground station. The memory is used to store computer programs. When the processor runs the computer programs stored in the memory, the processor executes the method of transmitting a unified global elevation benchmark using idle time and frequency signals.

[0097] The memory is connected to the processor. The memory can be flash memory, read-only memory or other types of memory. The processor can be a central processing unit or a microcontroller.

[0098] Furthermore, embodiments of this disclosure also provide a computer-readable storage medium storing a computer program, which is executed by a processor using the various possible methods described above.

[0099] The computer-readable storage medium includes volatile or non-volatile, removable or non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, computer program modules, or other data). Computer-readable storage media include, but are not limited to, RAM (Random Access Memory), ROM (Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), flash memory or other memory technologies, CD-ROM (Compact Disc Read-Only Memory), Digital Video Disc (DVD) or other optical disc storage, cartridges, magnetic tapes, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer.

[0100] In summary, the present invention relates to a method for unifying a global elevation datum using high-precision airborne time-frequency signals. This method utilizes a high-performance airborne (spacecraft-borne) optical clock to determine the gravity potential of ground stations via time-frequency transmission, establishes a high-precision conversion model between gravity potential and altitude, and converts the gravity potential of any point to a globally unified geoid, thereby achieving a unified global elevation datum.

[0101] This invention utilizes a high-precision optical clock mounted on a satellite or space station to perform time-frequency comparison with an optical clock at a ground station via an air-to-ground link. Since this method does not require laying optical fibers (cables), it is not limited by terrain conditions and can achieve elevation data transmission across oceans.

[0102] The method of this invention has three key technical aspects: First, to achieve time-frequency transmission with centimeter-level accuracy, high-precision optical clocks need to be set up at different locations, and the accuracy of the optical clocks needs to reach 10. -18 First, it requires the construction of a gravity potential and elevation conversion model covering the entire region, with the model accuracy meeting the centimeter-level accuracy requirements. Second, it requires the construction of a unified global elevation datum model to convert the elevations of any elevation datum surface at different points to a globally unified elevation datum surface, thereby achieving global elevation datum unification.

[0103] The method of this invention can overcome the shortcomings of traditional high-altitude measurement, such as high cost, low efficiency and poor accuracy, and realize cross-sea elevation measurement. It achieves global elevation benchmark unification with centimeter-level accuracy. It combines the principle of elevation benchmark unification with time and frequency transfer technology, and provides a brand-new research method for realizing global elevation benchmark unification.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for transmitting a unified global elevation datum using unloaded time-frequency signals, characterized in that: By integrating the transmission of idle time-frequency signals, the conversion of second-order gravity potential difference to altitude, and the global benchmark conversion, centimeter-level elevation transfer across continents is achieved, including: Obtain time-frequency observations based on unloaded time-frequency signal transmission; The gravity potential difference between the two ground stations is calculated based on the transmitted time-frequency observations. The elevation of the ground station to be measured on the regional geoid is obtained based on the conversion model between second-order gravity potential difference and elevation. The conversion model between second-order gravity potential difference and elevation is as follows: Wherein, ΔW PQ H represents the gravitational potential difference between the two locations. P This indicates that the altitude of ground station P is known to be high. This represents the average gravity value of the ground station Q to be measured. R represents the average gravity value at a known ground station P, and R represents the Earth's radius. Based on the elevation transformation relationship between the regional geoid and the globally unified elevation datum, the elevation on the regional geoid is transformed to the globally unified elevation datum; the elevation transformation relationship between the regional geoid and the globally unified elevation datum is as follows: in, W0 represents the gravity potential of the regional geoid, while W0 represents the gravity potential of the globally unified elevation datum. This represents the average gravity from the geoid at point P to the global geoid. H indicates that the elevation of the ground station P to be measured is high on the regional geoid. P This indicates that the altitude of the ground station P to be measured is high on the globally unified elevation datum. It represents the elevation difference between the regional geoid and the globally unified elevation datum.

2. The method for transmitting a unified global elevation datum using unloaded time-frequency signals according to claim 1, characterized in that, The method further includes: High-precision optical clocks are installed on both the space station and the ground station to provide time and frequency references; The space station and the ground station are connected by a space time-frequency transmission link for time-frequency comparison of optical clocks.

3. The method for transmitting a unified global elevation datum using unloaded time-frequency signals according to claim 2, characterized in that, Based on the transmitted time and frequency observations, the gravity potential difference between two ground stations is calculated, including: using the observations of high-precision optical clocks of the space station and the ground station, performing a time and frequency comparison between the space and ground optical clocks to obtain the gravity potential of any ground station; and obtaining the gravity potential difference between the two ground stations based on the known gravity potentials of the ground station and the ground station to be measured.

4. The method for transmitting a unified global elevation datum using unloaded time-frequency signals according to claim 2, characterized in that, Based on the transmitted time and frequency observations, the gravity potential difference between the two ground stations is calculated, including: using the observations of the high-precision optical clocks of the space station and the ground station, performing a ground-to-space-to-ground optical clock time and frequency comparison to obtain the gravity potential difference between the known ground station and the ground station to be measured.

5. The method for transmitting a unified global elevation datum using unloaded time-frequency signals according to claim 1, characterized in that, Given that ground station P is located on the geoid, the elevation of any point i to be measured is: Among them, C i Let i be the number of Earth positions at point i. Let be the average gravitational force at point i.

6. A system for transmitting a unified global elevation datum using unloaded time-frequency signals, characterized in that: By integrating the transmission of idle time-frequency signals, the conversion of second-order gravity potential difference to altitude, and the global benchmark conversion, centimeter-level elevation transfer across continents is achieved, including: The first main module is used to acquire time-frequency observations based on the transmission of idle time-frequency signals; The second main module is used to calculate the gravity potential difference between the two ground stations based on the transmitted time-frequency observations; The third main module is used to obtain the elevation of the ground station to be measured on the regional geoid based on the conversion model of second-order gravity potential difference and elevation height; the conversion model of second-order gravity potential difference and elevation height is as follows: Wherein, ΔW PQ H represents the gravitational potential difference between the two locations. P This indicates that the altitude of ground station P is known to be high. This represents the average gravity value of the ground station Q to be measured. R represents the average gravity value at a known ground station P, and R represents the Earth's radius. The fourth main module is used to convert the elevation on the regional geoid to the globally unified elevation datum based on the elevation conversion relationship between the regional geoid and the globally unified elevation datum. The elevation conversion relationship between the regional geoid and the globally unified elevation datum is as follows: in, W0 represents the gravity potential of the regional geoid, while W0 represents the gravity potential of the globally unified elevation datum. This represents the average gravity from the geoid at point P to the global geoid. H indicates that the elevation of the ground station P to be measured is high on the regional geoid. P This indicates that the altitude of the ground station P to be measured is high on the globally unified elevation datum. It represents the elevation difference between the regional geoid and the globally unified elevation datum.

7. A ground station device, characterized in that, It includes a high-precision clock, a memory, and a processor. The high-precision clock is used to provide frequency and time references for ground stations. The memory is used to store computer programs. When the processor runs the computer programs stored in the memory, the processor executes the method for transmitting a unified global elevation benchmark using an idle time-frequency signal as described in any one of claims 1 to 5.

8. A non-transitory computer read storage medium, characterized in that, The non-transitory computer read storage medium stores computer instructions, which cause the computer to execute the method of transmitting a unified global elevation datum using an idle time-frequency signal as described in any one of claims 1 to 5.

Images