WO2020244560A1 - Transmitting and receiving methods for differential correction data, system, and device - Google Patents

Abstract

The present application relates to the field of positioning, and discloses transmitting and receiving methods for differential correction data, a system, and a device. The differential correction data comprises a first, second, third, and fourth model polynomial coefficient of an oblique ionospheric correction algorithm model. The transmitting method comprises: a service end acquiring an ionospheric data range and a resolution of a current region; the service end separately determining, according to the ionospheric data range and the resolution of the current region, a bit length for at least one of the second, third, and fourth model polynomial coefficient; and the service end sending, according to the determined bit length, the at least one of the second, third, and fourth model polynomial coefficient to a user terminal. Embodiments of the present application perform customized arrangement and compression on differential correction data to reduce a large amount of transmission costs and time. In addition, the simplified data prevents an increase in the bit error rate caused by attenuation of a geosynchronous satellite signal transmitted across a long distance.

Description

Method, system and device for sending and receiving differential correction data Technical field

This application relates to positioning technology, in particular to compression technology of differential correction data.

Background technique

At present, there are many encoding formats adopted internationally for broadcasting high-precision correction data messages through satellites. For example, satellite FM forwards the standard RTCM format to the receiving end, which can realize real-time positioning and correction. However, the amount of data is huge and the transmission time is long. Refer to page 1 for reference, where SSR1-3 single transmission data is in the order of millions of bits; and the compact SSR technical standard adopted by the existing QZSS is only applicable to Japan, and most of the formats do not conform to Chinese domestic standards. For positioning requirements, please refer to page 2 for reference, where SSR1-3 single transmission data is in the order of million bits. However, none of the formats in the specific PPP-RTK technology solves the compression problem of the information coding format under the large demand for high concurrency and low delay, so that the channel redundancy increases and the utilization rate decreases.

Summary of the invention

The purpose of this application is to provide a method, system and device for sending and receiving differential correction data, which arranges and compresses the differential correction data in a targeted manner, so that the transmission cost and time are greatly saved, and because the data is simplified, the reduction The bit error rate increases due to the long transmission distance of the synchronous satellite signal and the large fading.

The present application discloses a method for sending differential correction data. The differential correction data includes the first, second, third, and fourth model polynomial coefficients of the oblique ionospheric correction algorithm model, and the sending method includes:

The server obtains the range and resolution of ionospheric data in the current region;

The server separately determines the bit length of at least one of the second, third, and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region;

The server sends at least one of the second, third and fourth model polynomial coefficients to the user terminal according to the determined bit length.

In a preferred example, the server separately determines the bit length of at least one of the second, third, and fourth model polynomial coefficients according to the range and resolution of the ionospheric data of the current region, which further includes:

The server determines a preset threshold range according to the resolution;

If the ionospheric data range is within the preset threshold range, the bit length of at least one of the second, third and fourth model polynomial coefficients is the first bit length, otherwise it is the second bit length, where The first bit length is less than the second bit length.

In a preferred example, the server separately determines the bit length of at least one of the second, third, and fourth model polynomial coefficients according to the range and resolution of the ionospheric data of the current region, which further includes:

The server separately determines the required bit length of at least one of the second, third and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region;

The server separately determines whether the bit length of at least one of the second, third, and fourth model polynomial coefficients is the first bit length or the second bit length according to the required bit length.

In a preferred example, before the server separately determines the bit length of at least one of the second, third, and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region, the method further includes:

The server presets an expanded function data pointer, and the expanded function data pointer is used to switch at least one of the second, third, and fourth model polynomial coefficients between the first bit length and the second bit length.

In a preferred example, the expansion function data pointer is 3-bit binary data, wherein each bit indicates whether the expansion function is enabled for the second, third, and fourth model polynomial coefficients.

The present application also discloses a system for transmitting differential correction data. The differential correction data includes the first, second, third and fourth model polynomial coefficients of the oblique ionospheric correction algorithm model, including:

The acquisition module is used to acquire the ionospheric data range and resolution of the current region;

A processing module for determining the bit length of at least one of the second, third, and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region;

The sending module sends at least one of the second, third and fourth model polynomial coefficients to the user terminal according to the determined bit length.

In a preferred example, the processing module is further configured to determine a preset threshold range according to the resolution, and if the ionospheric data range is within the preset threshold range, the second, third, and The bit length of at least one of the fourth model polynomial coefficients is the first bit length, otherwise it is the second bit length, wherein the first bit length is less than the second bit length.

In a preferred example, the processing module is further configured to determine the required bit length of at least one of the second, third, and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region , And respectively determine whether the bit length of at least one of the second, third and fourth model polynomial coefficients is the first bit length or the second bit length according to the required bit length.

In a preferred example, the processing module makes the bit length of at least one of the second, third and fourth model polynomial coefficients between the first bit length and the second bit length through a preset expansion function data pointer. Switch between.

In a preferred example, the expansion function data pointer is 3-bit binary data, wherein each bit indicates whether the expansion function is enabled for the second, third, and fourth model polynomial coefficients.

This application also discloses a method for receiving differential correction data, including:

The user terminal receives differential correction data from the server, where the differential correction data includes the first, second, third, and fourth model polynomial coefficients of the oblique ionospheric correction algorithm model;

The user terminal separately determines the bit length of at least one of the second, third, and fourth model polynomial coefficients;

The user terminal decodes at least one of the second, third and fourth model polynomial coefficients according to the determined bit length.

In a preferred example, the user terminal separately determining the bit length of at least one of the second, third, and fourth model polynomial coefficients further includes:

The user terminal determines that the bit length of at least one of the second, third, and fourth model polynomial coefficients is the first bit length or the second bit length;

If it is the first bit length, decode at least one of the second, third and fourth model polynomial coefficients according to the first bit length;

If it is the second bit length, decode at least one of the second, third and fourth model polynomial coefficients according to the second bit length.

In a preferred example, the differential correction data further includes a preset expansion function data pointer, and the expansion function data pointer is used to make at least one of the second, third and fourth model polynomial coefficients in the first bit. Switch between length and second bit length;

The user terminal separately determining the bit length of at least one of the second, third and fourth model polynomial coefficients further includes:

The user terminal determines whether the bit length of at least one of the second, third, and fourth model polynomial coefficients is the first bit length or the second bit length according to the preset expansion function data pointer.

In a preferred example, the expansion function data pointer is 3-bit binary data, wherein each bit indicates whether the expansion function is enabled for the second, third, and fourth model polynomial coefficients.

The application also discloses a device for transmitting differential correction data, including:

Memory for storing computer executable instructions; and,

The processor is used to implement the steps in the method described above when executing the computer-executable instructions.

This application also discloses a method for sending differential correction data, the differential correction data including the first, second and third model polynomial coefficients of the oblique ionospheric correction algorithm model, and the sending method includes:

The server obtains the range and resolution of ionospheric data in the current region;

The server separately determines the bit length of at least one of the second and third model polynomial coefficients according to the ionospheric data range and resolution of the current region;

The server sends at least one of the second and third model polynomial coefficients to the user terminal according to the determined bit length.

In a preferred example, the server separately determines the bit length of at least one of the second and third model polynomial coefficients according to the ionospheric data range and resolution of the current region, which further includes:

The server determines a preset threshold range according to the resolution;

If the ionospheric data range is within the preset threshold range, the bit length of at least one of the second and third model polynomial coefficients is the first bit length, otherwise it is the second bit length. The length of one bit is less than the length of the second bit.

In a preferred example, the server separately determines the bit length of at least one of the second and third model polynomial coefficients according to the ionospheric data range and resolution of the current region, which further includes:

The server separately determines the required bit length of at least one of the second and third model polynomial coefficients according to the ionospheric data range and resolution of the current region;

The server separately determines whether the bit length of at least one of the second and third model polynomial coefficients is the first bit length or the second bit length according to the required bit length.

In a preferred example, before the server separately determines the bit length of at least one of the second and third model polynomial coefficients according to the ionospheric data range and resolution of the current region, the method further includes:

The server presets an expanded function data pointer, and the expanded function data pointer is used to switch at least one of the second and third model polynomial coefficients between the first bit length and the second bit length.

In a preferred example, the expansion function data pointer is 2-bit binary data, wherein each bit respectively indicates whether the expansion function is enabled for the second and third model polynomial coefficients.

The application also discloses a device for transmitting differential correction data, including:

Memory for storing computer executable instructions; and,

The processor is used to implement the steps in the method described above when executing the computer-executable instructions.

The compressed or compressed format of the regional atmospheric correction data in the embodiment of this application may be based on the RTCM standard message format and with reference to the formatting method of the Japanese QZSS system, which can be based on the differential correction data of the currently existing and available GNSS system. Targeted arrangement and compression.

First of all, for regions with active ionosphere (such as Shenzhen or Guangzhou in China), the upper and lower limits of the ionospheric correction data are extremely large (for example, most of the data range in Figure 2 falls within the ±20 range, and a small part of the data range falls within the range of ±20. ±100 interval), taking type2 as an example, the calculation shows that the data volume of the second, third and fourth model polynomial coefficients (C ₀₁ , C ₁₀ and C ₁₁ ) in the ±100 interval in this area are 14 bits respectively. However, the 12, 12, or 10 bit length in the traditional RTCM format cannot be expressed, which greatly hinders the use of user terminal data and cannot meet the user scenario. If the range is simply expanded, for example, the length is expanded to 14 bits. For those falling in the ±20 interval, a large amount of channel idle waste is generated. In the embodiment of this application, the required bit lengths of C ₀₁ , C ₁₀ and C ₁₁ in the differential correction data can be determined according to the range and resolution of the ionospheric data in the current region, and the settings can be set between the first bit length and the first bit length. Two-bit length selection pointer for C ₀₁ , C ₁₀ and C _{11 to} select compression, for example, according to the above-mentioned most of them fall in the ±20 interval and a small part of them in the ±100 interval, two options of 12-bit length and 14-bit length are set respectively , Then the problem of channel idle waste is avoided. Further, the selection pointer can increase the flexibility of bit length selection of C ₀₁ , C ₁₀ and C ₁₁ , and further reduce invalid data bits. For example, the selection pointer is set to 3-bit binary data (for example: xxx, where x is 0 or 1), it is possible for the C _01, C ₁₀ and C ₁₁ are set, for example, is provided for C ₀₁ has 12-bit length (0) and a 14-bit length (1), has 12-bit length for C ₁₀ settings (0 ) And 14-bit length (1). For C ₁₁ , 10 bit length (0) and 14-bit length (1) are set. Then the 3-bit binary data xxx has 8 options such as 000, 001, 010, 011, 100, 101, 110, 111, which can be greatly reduced Invalid data bits, which greatly improves the channel utilization.

Furthermore, while making up for the shortcomings of the original RTCM format, the implementation of the present application also reduces invalid data bits, which saves a lot of transmission cost and time, and because the data is simplified, it reduces the transmission distance and fading of synchronous satellite signals. The bit error rate caused by the big increase.

Furthermore, for the QZSS coding system, the technical indicators have been redefined according to the specific conditions of different regions. For example, the correctable range and grid range are improved for the Chinese region, so that the corrected data information is consistent with China's geographic location while maintaining high accuracy. Situation, land area and atmospheric conditions. In addition, on the basis of QZSS coding, the total data volume of broadcast information is also reduced.

A large number of technical features are recorded in the specification of this application, which are distributed in various technical solutions. If all possible combinations of technical features (ie, technical solutions) of this application are to be listed, the specification will be too long. In order to avoid this problem, the various technical features disclosed in the above invention content of this application, the various technical features disclosed in the various embodiments and examples below, and the various technical features disclosed in the drawings can be freely combined with each other to form Various new technical solutions (these technical solutions are deemed to have been recorded in this specification), unless such a combination of technical features is technically infeasible. For example, in one example, the feature A+B+C is disclosed, and in another example, the feature A+B+D+E is disclosed, and the features C and D are equivalent technical means that play the same role. Technically, just choose It can be used once and cannot be used at the same time. Feature E can be combined with feature C technically. Then, the solution of A+B+C+D should not be regarded as documented due to technical infeasibility, and A+B+ The C+E plan should be deemed to have been documented.

Description of the drawings

FIG. 1 is a schematic flowchart of a method for sending differential correction data according to the first embodiment of the present application;

Figure 2 is an example of active ionospheric data in a certain area of China;

3 is a schematic structural diagram of a system for transmitting differential correction data according to the second embodiment of the present application;

4 is a schematic flowchart of a method for receiving differential correction data according to a third embodiment of the present application;

5 is a schematic structural diagram of a receiving system for differential correction data according to a fourth embodiment of the present application;

Fig. 6 is an example in which the data range and resolution are individually set to ±100 according to this application to meet a large number of channel empty loads under special circumstances;

Fig. 7 is a schematic flowchart of a method for sending differential correction data according to a fifth embodiment of the present application.

Detailed ways

In the following description, many technical details are proposed in order to enable readers to better understand this application. However, those of ordinary skill in the art can understand that even without these technical details and various changes and modifications based on the following embodiments, the technical solution claimed in this application can be realized.

Explanation of some concepts:

Global Navigation Satellite System (Global Navigation Satellite System), abbreviated as: GNSS.

Beidou Navigation Satellite System (BDS navigation Satellite system), abbreviated as: BDS.

State Space Representation (State Space Representation), referred to as SSR.

Precise Point Positioning, referred to as PPP.

Carrier phase real-time dynamic difference (Real Time Kinematic), referred to as RTK.

Transmission Control/Internet Protocol (Transmission Control/Internet Protocol), referred to as TCP/IP.

Internet-based RTCM data transmission protocol (Networked Transport of RTCM via Internet), abbreviated as: NTRIP.

Radio Technical Commission for Maritime Services (Radio Technical Commission for Maritime Services), referred to as RTCM.

Quasi-Zenith Satellite System (Quasi-Zenith Satellite System), abbreviated as: QZSS.

Total Electron Content Unit (Total Electron Content Unit), referred to as TECU.

The total electron content of the oblique ionosphere, STEC.

In order to make the objectives, technical solutions, and advantages of the present application clearer, the implementation manners of the present application will be further described in detail below in conjunction with the accompanying drawings.

The first embodiment of the present application relates to a method for transmitting differential correction data. The differential correction data includes the first, second, third, and fourth model polynomial coefficients of the oblique ionospheric correction algorithm model. The flow of the transmission method As shown in Figure 1, the sending method includes the following steps:

To start, go to step 101, the server obtains the ionospheric data range and resolution of the current region.

In the STEC correction, when a certain resolution is guaranteed, the upper and lower limit constraints need to be set according to the ionospheric activity over the current area, otherwise the positioning effect will not be achieved, and even the opposite effect will be produced. The active degree of the ionosphere itself is strongly related to latitude, that is, the ionosphere is approximately active closer to the equator, resulting in a larger correction number range and a smaller resolution, and the result is an increase in data volume. The relationship is expressed as the following formula (1):

Ionospheric data range (or the range of the upper and lower limits of the ionosphere)

= 2 ^{bits -1} * ionospheric resolution (TECU) (1)

Therefore, combined with the conventional RTCM encoding format data table of Table 2 mentioned below, as an understanding, the bit length (14/12/10) is the x power of 2 in the formula, and the product of the ionospheric resolution (TECU) is Data range of the ionosphere. This formula (1) is applied to the encoding of the physical layer included in the RTCM protocol specification, and its expression is: for example, Xxxxxxxx (X/x is 1 or 0), where X is the sign bit, which represents the ionosphere in Table 2. The positive and negative of the upper and lower limits (for example: ±409.4) occupies 1 bit; x is the data bit, which represents the positive and negative value (409.4) of the upper and lower limits of the ionosphere (for example: ±409.4) in Table 2, according to The increasing number of data will also increase, and the relationship is (maximum value = 2 ^x ). For example, if the range data of the upper and lower limits of the ionosphere is -8, the corresponding binary data is: 1 1000, the first 1 represents the negative sign (sign bit), and 1000 represents the binary number 8 (data bit), a total of 5 bits. According to this calculation method, we know that the larger the range of the upper and lower limits of the ionosphere, the more bits x needs to represent, and X is not affected. Therefore, according to the local facts in China, in areas where the ionosphere is active (within a network), such as cities such as Shenzhen and Guangzhou, the upper and lower ranges are extremely large. Figure 2 is the "Ionospheric Active Data Map" of a certain region in China. It can be seen from Figure 2 that the data distribution ranges from ±10 to +100 to -40. If the traditional RTCM method is used, refer to Table 2, its feasibility As: C _{00 is} satisfied, C ₀₁ C ₁₀ C _{11 is} not satisfied. It can be seen that the traditional RTCM method has three coefficients that cannot even represent this data, which greatly hinders the data application of the user terminal and cannot meet the user scenario. If the scope is expanded, the data volume will increase further based on the above derivation. Therefore, in step 101 of this embodiment, first obtain the ionospheric data range and resolution of the current region, and then further compress and process the differential correction data for the ionospheric data range and resolution of different regions. This can be adapted to local conditions. Correct the data for optimization, so as to achieve the problem of compressing the overall data volume.

Then, in step 102, the server separately determines the bit length of at least one of the second, third, and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region.

Because, continue to take Figure 2 as an example, most of the data in the figure falls in the ±20 interval, while a small amount of data is within ±40 or even higher. During the broadcasting process, if the data range and resolution are individually set to ±100 to meet special conditions, a large amount of channel idle waste (or more invalid data bits) will occur, as shown in Figure 6. In order to represent the situation of ±100, in the case of the resolution of 0.02TECU, the real data is: 2 ¹³ *0.02=163.84 total 13btis, plus a sign bit 14bits. Compare the data of C ₀₁ C ₁₀ C _{11 in} Table 2, all of which exceed the data volume. And if the format in Table 2 is changed to 14 digits, the overall data volume will increase further according to formula (1) and formula (2) mentioned below. Therefore, in step 102 of this embodiment, for some or all of the second, third, and fourth model polynomial coefficients C ₀₁ C ₁₀ C ₁₁ , based on the current area ionospheric data range and resolution obtained in step 101 Rate to determine their bit length, solve the aforementioned problem of invalid data bits, so that each data bit can have a specific meaning and minimize empty bits, thereby greatly improving the channel utilization rate. Further, in this embodiment, two choices of "first bit length" and "second bit length" are set for each coefficient of the second, third and fourth model polynomial coefficients. According to calculations, if set to More choices (such as three choices) will add more extra bits, so two choices are the best. Further, in this step 102, "at least one of the second, third and fourth model polynomial coefficients" may be any one, or any two, or three of the second, third and fourth model polynomial coefficients. .

There are many ways to implement this step 102. Optionally, this step 102 may be further implemented by the following steps: the server determines a preset threshold range according to the resolution, and if the ionospheric data range is within the preset threshold range, the second, third, and third steps The bit length of at least one of the four-model polynomial coefficients is the first bit length, otherwise it is the second bit length, wherein the first bit length is greater than or less than the second bit length. Optionally, this step 102 can be further implemented by the following steps: the server separately determines the required bits of at least one of the second, third and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region Length, the server separately determines whether the bit length of at least one of the second, third, and fourth model polynomial coefficients is the first bit length or the second bit length according to the required bit length. But it is not limited to these two implementations. Specifically, the bit length of at least one of the second, third, and fourth model polynomial coefficients is determined respectively. In the type1 of Table 5, it is shown as determining the bit length of at least one of C ₀₁ and C ₁₀ , that is, further, Determine the bit length of at least one of the polynomial coefficients of the second and third models according to the range and resolution of the ionospheric data in the current region; in type 2, it is represented as determining the bit of at least one of C ₀₁ , C ₁₀ and C ₁₁ length.

Optionally, in this embodiment, for the second, third, and fourth model polynomial coefficients, the first bit lengths set for the three may be the same or different, and are the first bit lengths set for the three. The length of the two bits can be the same or different. It can be set according to the current ionospheric data range and resolution.

Optionally, the step 102 also includes the following step: the server presets an expanded function data pointer, and the expanded function data pointer is used to make the bit length of at least one of the second, third, and fourth model polynomial coefficients Flexible switching between the first bit length and the second bit length.

There are many ways to set the expanded function data pointer. Optionally, the expanded function data pointer may be 1 bit in length, and may be used to indicate one coefficient of the second, third, and fourth model polynomial coefficients or indicate two or three coefficients at the same time; for example, it may be used for Indicate one coefficient of the second, third, and fourth model polynomial coefficients and enable the bit length of the one coefficient to be flexibly switched between the first bit length and the second bit length, or can be used to indicate the second, The two coefficients in the third and fourth model polynomial coefficients and make the bit length of the two coefficients flexibly switch between the first bit length and the second bit length, or can be used to indicate the second and third bit lengths simultaneously And three coefficients in the fourth model polynomial coefficients, and the bit length of the three coefficients can be flexibly switched between the first bit length and the second bit length. Optionally, the expanded function data pointer may have a length of 2 bits, where each bit may be used to indicate one coefficient of the second, third, and fourth model polynomial coefficients or indicate two coefficients at the same time; for example, each The bits respectively indicate one of the second, third and fourth model polynomial coefficients and the bit length of the one coefficient can be flexibly switched between the first bit length and the second bit length, or one of the bits can be used for simultaneous Indicate two coefficients in the second, third, and fourth model polynomial coefficients and the other bit is used to indicate the third coefficient in the second, third, and fourth model polynomial coefficients, and make the three coefficients The bit length of is flexibly switched between the first bit length and the second bit length, etc. Optionally, the expanded function data pointer may have a length of 3 bits and are used to indicate three coefficients of the second, third, and fourth model polynomial coefficients; and so on.

In an embodiment, the expansion function data pointer is 3-bit binary data, wherein each bit indicates whether the expansion function is enabled for the second, third, and fourth model polynomial coefficients, so that the second, third, and The fourth model polynomial coefficients are flexibly switched between the first bit length and the second bit length.

Optionally, the expansion function data pointer is 3-bit binary data, wherein each bit indicates whether the expansion function is enabled for the second, third, and fourth model polynomial coefficients. The following Table 1 is a specific embodiment of the compression format of step 102. Among them, the three-bit binary data (for example: xxx) respectively indicate whether the expansion function is enabled for the three coefficients, if 0 is not enabled, and 1 is enabled. It is ensured that the second, third and fourth model polynomial coefficients C ₀₁ C ₁₀ C ₁₁ can be flexibly switched between 12-bit length/12-bit length/10-bit length and required length L, respectively.

Table 1

Then, in step 103, the server sends at least one of the second, third, and fourth model polynomial coefficients to the user terminal according to the determined bit length.

Optionally, the differential correction data may also include data such as GNSS satellite identification (ID).

It can also be seen from the above that the implementation of this application can flexibly select the upper and lower limits of the encoding format and its corresponding resolution according to the different ionospheric activity levels in China, and solve the aforementioned invalid data bit problem, so that each data bit can have a specific Significance and minimize the empty bits, so that the channel utilization rate is greatly improved. Example: Somewhere in China, after calculation, the corrected data is compared with the conventional compression method of RTCM ① and the method of sending (compression) in the implementation of this application ② as shown in the following Table 2. Through comparison, it can be seen that: 30 seconds to 1 minute), the satellite throughput saved is 960,000 bits. Today, when satellite throughput is so cherished and the price is so high, the advantages of this saved resource are self-evident.

Table 2

The second embodiment of the present application relates to a differential correction data transmission system. The differential correction data includes the first, second, third and fourth model polynomial coefficients of the oblique ionospheric correction algorithm model. The structure of the transmission system is shown in the figure As shown in 3, the sending system includes an acquisition module, a processing module, and a sending module.

First, the acquisition module is used to acquire the ionospheric data range and resolution of the current region.

In the STEC correction, when a certain resolution is guaranteed, the upper and lower limit constraints need to be set according to the ionospheric activity over the current area, otherwise the positioning effect will not be achieved, and even the opposite effect will be produced. The active degree of the ionosphere itself is strongly related to latitude, that is, the ionosphere is approximately active closer to the equator, resulting in a larger correction number range and a smaller resolution, and the result is an increase in data volume. The relationship is expressed as the following formula (1):

Ionospheric data range (range of the upper and lower limits of the ionosphere)

＝2 ^{bits -1} *Ionospheric resolution (TECU) (1)

Therefore, combined with the conventional RTCM encoding format data table of Table 2 mentioned below, as an understanding, the bit length (14/12/10) is the x power of 2 in the formula, and the product of the ionospheric resolution (TECU) is Data range of the ionosphere. This formula (1) is applied to the encoding of the physical layer included in the RTCM protocol specification, and its expression is: for example, Xxxxxxxx (X/x is 1 or 0), where X is the sign bit, which represents the ionosphere in Table 2. The positive and negative of the upper and lower limits (for example: ±409.4) occupies 1 bit; x is the data bit, which represents the positive and negative value (409.4) of the upper and lower limits of the ionosphere (for example: ±409.4) in Table 2, according to The increasing number of data will also increase, and the relationship is (maximum value = 2 ^x ). For example, if the range data of the upper and lower limits of the ionosphere is -8, the corresponding binary data is: 1 1000, the first 1 represents the negative sign (sign bit), and 1000 represents the binary number 8 (data bit), a total of 5 bits. According to this calculation method, we know that the larger the range of the upper and lower limits of the ionosphere, the more bits x needs to represent, and X is not affected. Therefore, according to the local facts in China, in areas where the ionosphere is active (within a network), such as cities such as Shenzhen and Guangzhou, the upper and lower ranges are extremely large. Figure 2 is the "Ionospheric Active Data Map" of a certain region in China. It can be seen from Figure 2 that the data distribution ranges from ±10 to +100 to -40. If the traditional RTCM method is used, refer to Table 2, its feasibility As: C _{00 is} satisfied, C ₀₁ C ₁₀ C _{11 is} not satisfied. It can be seen that the traditional RTCM method has three coefficients that cannot even represent this data, which greatly hinders the data application of the user terminal and cannot meet the user scenario. If the scope is expanded, the data volume will increase further based on the above derivation. Therefore, in this embodiment, the current region's ionospheric data range and resolution are acquired through the acquisition module, and the differential correction data for the ionospheric data range and resolution of different regions is further compressed. This can be adapted to local conditions and partially corrected The data is optimized to achieve the problem of compressing the overall data volume.

Further, the processing module is used to determine the bit length of at least one of the second, third and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region. Because, continue to take Figure 2 as an example, most of the data in the figure falls in the ±20 interval, while a small amount of data is within ±40 or even higher. During the broadcasting process, if the data range and resolution are individually set to ±100 to meet special conditions, a large amount of channel idle waste (or more invalid data bits) will occur, as shown in Figure 6. In order to represent the situation of ±100, in the case of the resolution of 0.02TECU, the real data is: 2 ¹³ *0.02=163.84 total 13btis, plus a sign bit 14bits. Comparing the data of C ₀₁ C ₁₀ C _{11 in} Table 2, all exceed the data volume. And if the format in Table 2 is changed to 14 digits, the overall data volume will increase further according to formula (1) and formula (2) mentioned below. Therefore, in this embodiment, through the processing module, for some or all of the polynomial coefficients C ₀₁ C ₁₀ C ₁₁ of the second, third, and fourth models, the range and resolution of the ionospheric data in the current region acquired by the acquisition module are To determine their bit length, solve the aforementioned invalid data bit problem, so that each data bit can have a specific meaning and minimize the empty bits, so that the channel utilization rate is greatly improved. Further, in this embodiment, two choices of "first bit length" and "second bit length" are set for each coefficient of the second, third and fourth model polynomial coefficients. According to calculations, if set to More choices (such as three choices) will add more extra bits, so two choices are the best. Further, the “at least one of the second, third, and fourth model polynomial coefficients” may be any one, or any two, or three of the second, third, and fourth model polynomial coefficients.

Optionally, the processing module is further configured to determine a preset threshold range according to the resolution. If the ionospheric data range is within the preset threshold range, at least one of the second, third, and fourth model polynomial coefficients The bit length of is the first bit length, otherwise it is the second bit length, where the first bit length is greater than or less than the second bit length.

Optionally, the processing module is further configured to determine the required bit length of at least one of the second, third, and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region, and according to the required The bit length respectively determines whether the bit length of at least one of the second, third and fourth model polynomial coefficients is the first bit length or the second bit length.

Optionally, in this embodiment, for the second, third, and fourth model polynomial coefficients, the first bit lengths set for the three may be the same or different, and are the first bit lengths set for the three. The length of the two bits can be the same or different. It can be set according to the current ionospheric data range and resolution.

Optionally, the processing module enables at least one of the second, third and fourth model polynomial coefficients to be flexibly switched between the first bit length and the second bit length through a preset expansion function data pointer.

There are many ways to set the expanded function data pointer. Optionally, the expanded function data pointer may be 1 bit in length, and may be used to indicate one coefficient of the second, third, and fourth model polynomial coefficients or indicate two or three coefficients at the same time; for example, it may be used for Indicate one coefficient of the second, third, and fourth model polynomial coefficients and enable the bit length of the one coefficient to be flexibly switched between the first bit length and the second bit length, or can be used to indicate the second, The two coefficients in the third and fourth model polynomial coefficients and make the bit length of the two coefficients flexibly switch between the first bit length and the second bit length, or can be used to indicate the second and third bit lengths simultaneously And three coefficients in the fourth model polynomial coefficients, and the bit length of the three coefficients can be flexibly switched between the first bit length and the second bit length. Optionally, the expanded function data pointer may have a length of 2 bits, where each bit may be used to indicate one coefficient of the second, third, and fourth model polynomial coefficients or indicate two coefficients at the same time; for example, each The bits respectively indicate one of the second, third and fourth model polynomial coefficients and the bit length of the one coefficient can be flexibly switched between the first bit length and the second bit length, or one of the bits can be used for simultaneous Indicate two coefficients in the second, third, and fourth model polynomial coefficients and the other bit is used to indicate the third coefficient in the second, third, and fourth model polynomial coefficients, and make the three coefficients The bit length of is flexibly switched between the first bit length and the second bit length, etc. Optionally, the expanded function data pointer may have a length of 3 bits, and are used to indicate three coefficients of the second, third, and fourth model polynomial coefficients; and so on.

In an embodiment, the expansion function data pointer is 3-bit binary data, wherein each bit indicates whether the expansion function is enabled for the second, third, and fourth model polynomial coefficients, so that the second, third, and The fourth model polynomial coefficients are flexibly switched between the first bit length and the second bit length.

Optionally, the expansion function data pointer is 3-bit binary data, wherein each bit indicates whether the expansion function is enabled for the second, third, and fourth model polynomial coefficients.

Further, the sending module sends at least one of the second, third and fourth model polynomial coefficients to the user terminal according to the determined bit length.

Optionally, the differential correction data may also include data such as GNSS satellite identification (ID).

The first embodiment is a method embodiment corresponding to this embodiment. The technical details in the first embodiment can be applied to this embodiment, and the technical details in this embodiment can also be applied to the first embodiment.

The third embodiment of the present application relates to a method for receiving differential correction data. The process is shown in FIG. 4, and the method includes the following steps:

Initially, in step 301, the user terminal receives differential correction data from the server, the differential correction data includes the first, second, third, and fourth model polynomial coefficients of the oblique ionospheric correction algorithm model.

Optionally, the differential correction data may also include data such as GNSS satellite identification (ID).

Then, in step 302, the user terminal determines the bit length of at least one of the second, third, and fourth model polynomial coefficients.

Optionally, step 302 may be further implemented by the following steps: the user terminal determines that the bit length of at least one of the second, third, and fourth model polynomial coefficients is the first bit length or the second bit length, if it is the first bit length Bit length, decode at least one of the second, third, and fourth model polynomial coefficients according to the first bit length; if it is the second bit length, decode the second, third, and third coefficients according to the second bit length At least one of the fourth model polynomial coefficients.

Optionally, the differential correction data may further include a preset expansion function data pointer, and the expansion function data pointer is used to make the bit length of at least one of the second, third, and fourth model polynomial coefficients equal to the first bit length. Flexible switching between and the second bit length.

In step 303, "the user terminal determines that the bit length of at least one of the second, third, and fourth model polynomial coefficients is the first bit length or the second bit length" can be implemented in many ways. In one embodiment, the differential correction data sent on the server is in the format of a message, wherein the message header of the message contains a bit length indicating at least one of the second, third, and fourth model polynomial coefficients Identification bit. After receiving the differential correction data of the message format, the user terminal can first determine according to its identification bit that the bit length of at least one of the second, third and fourth model polynomial coefficients is the first bit length or The second bit length. In another embodiment, the differential correction data may further include a preset expansion function data pointer, and the bit of at least one of the second, third, and fourth model polynomial coefficients may be determined according to the preset expansion function data pointer. The length is the first bit length or the second bit length. But it is not limited to the above two embodiments.

There are many ways to set the expanded function data pointer. Optionally, the expanded function data pointer may be 1 bit in length, and may be used to indicate one coefficient of the second, third, and fourth model polynomial coefficients or indicate two or three coefficients at the same time; for example, it may be used for Indicate one coefficient of the second, third, and fourth model polynomial coefficients and enable the bit length of the one coefficient to be flexibly switched between the first bit length and the second bit length, or can be used to indicate the second, The two coefficients in the third and fourth model polynomial coefficients and make the bit length of the two coefficients flexibly switch between the first bit length and the second bit length, or can be used to indicate the second and third bit lengths simultaneously And three coefficients in the fourth model polynomial coefficients, and the bit length of the three coefficients can be flexibly switched between the first bit length and the second bit length. Optionally, the expanded function data pointer may have a length of 2 bits, where each bit may be used to indicate one coefficient of the second, third, and fourth model polynomial coefficients or indicate two coefficients at the same time; for example, each The bits respectively indicate one of the second, third and fourth model polynomial coefficients and the bit length of the one coefficient can be flexibly switched between the first bit length and the second bit length, or one of the bits can be used for simultaneous Indicate two coefficients in the second, third, and fourth model polynomial coefficients, and the other bit is used to indicate the third coefficient in the second, third, and fourth model polynomial coefficients, and make the three coefficients The bit length of is flexibly switched between the first bit length and the second bit length, etc. Optionally, the expanded function data pointer may have a length of 3 bits, and are used to indicate three coefficients of the second, third, and fourth model polynomial coefficients; and so on.

Optionally, the expansion function data pointer is 3-bit binary data, wherein each bit indicates whether the expansion function is enabled for the second, third, and fourth model polynomial coefficients, and the second, third, and first The four-model polynomial coefficients can be flexibly switched between the first bit length and the second bit length. Table 1 above is a specific example of the compression format in this embodiment.

Then, in step 303, the user terminal decodes at least one of the second, third and fourth model polynomial coefficients according to the determined bit length.

The fourth embodiment of the present application relates to a receiving system for differentially corrected data, the structure of which is shown in FIG. 5, and the system includes a receiving module and a processing module.

First, the receiving module is used to receive differential correction data from the server, the differential correction data including the first, second, third, and fourth model polynomial coefficients of the oblique ionospheric correction algorithm model.

Further, the processing module is used to determine the bit length of at least one of the second, third and fourth model polynomial coefficients, and the user terminal decodes the second, third and fourth model polynomials according to the determined bit length At least one of the coefficients.

The third embodiment is a method embodiment corresponding to this embodiment. The technical details in the third embodiment can be applied to this embodiment, and the technical details in this embodiment can also be applied to the third embodiment.

The fifth embodiment of the present application relates to a method for sending differential correction data. The differential correction data includes the first, second, and third model polynomial coefficients of the oblique ionospheric correction algorithm model, as shown in the flowchart of FIG. 7 , The sending method includes the following steps:

In step 701, the server obtains the ionospheric data range and resolution of the current region.

Then, in step 702, the server separately determines the bit length of at least one of the second and third model polynomial coefficients according to the ionospheric data range and resolution of the current region.

There are many ways to implement this step 702. Optionally, step 702 can be further implemented as: the server determines a preset threshold range according to the resolution; if the ionospheric data range is within the preset threshold range, the second and third model polynomial coefficients The bit length of at least one is the first bit length, otherwise it is the second bit length, wherein the first bit length is less than the second bit length. Optionally, step 702 can be further implemented as: the server determines the required bit length of at least one of the second and third model polynomial coefficients according to the ionospheric data range and resolution of the current region; the server According to the required bit length, it is determined whether the bit length of at least one of the second and third model polynomial coefficients is the first bit length or the second bit length.

Optionally, before step 702, the following step may be further included: the server presets an expanded function data pointer, and the expanded function data pointer is used to make at least one of the second and third model polynomial coefficients in the first bit length Switch between and the second bit length.

Optionally, the expansion function data pointer is 2-bit binary data, wherein each bit respectively indicates whether the expansion function is enabled for the second and third model polynomial coefficients.

After that, in step 703, the server sends at least one of the second and third model polynomial coefficients to the user terminal according to the determined bit length.

The sixth embodiment of the present application relates to a system for transmitting differential correction data. The differential correction data includes the first, second, and third model polynomial coefficients of the oblique ionospheric correction algorithm model. As shown in FIG. 8, the transmission The system includes acquisition module, processing module and sending module.

The acquisition module is used for the server to acquire the ionospheric data range and resolution of the current region.

The processing module is used for the server to determine the bit length of at least one of the second and third model polynomial coefficients respectively according to the ionospheric data range and resolution of the current region.

The sending module is used for the server to send at least one of the second and third model polynomial coefficients to the user terminal according to the determined bit length.

The fifth embodiment is a method embodiment corresponding to this embodiment. The technical details in the fifth embodiment can be applied to this embodiment, and the technical details in this embodiment can also be applied to the fifth embodiment.

The following is a brief introduction to some related technologies involved in the implementation of this application:

The or compressed format of the regional atmospheric correction data in this application is based on the RTCM standard message format, and refers to the format of the Japanese QZSS system (refer to web pages 3 and 4), and the correction data of the existing and available GNSS system Made targeted arrangement and compression.

GPS differential protocol and differential telegram algorithm are two issues that the differential system must consider. In a differential positioning application system, a large number of differential messages must be transmitted between the positioning terminal and the differential station. Since the positioning terminal is often a high-speed mobile target, in order to establish a data channel between the positioning terminal and the differential station, the traditional method is to use wireless communication. (Such as shortwave or ultrashortwave), the bottom interface usually adopts serial port (RS232/422), and the two parties communicate in byte mode. In order to adapt to this communication mode and realize the basic requirements of high efficiency and error control, the international standard RTCM 10403.2 has been formulated . With the continuous development of communication means, a large number of network methods are used to establish data links between the positioning terminal and the differential station. The data of the network communication is exchanged according to the data packet, and the errors are effectively controlled at the data link layer, and the price is low. Error, high-efficiency, and high-speed network communication brings new development opportunities to differential positioning applications. In order to adapt to the characteristics of network transmission, the RTCM 10403.1 standard has been formulated internationally and the network is now the main method.

The RTCM protocol specification includes application layer, presentation layer, transport layer, data link layer and physical layer. The most important thing for encoding and decoding is the arrangement at the physical layer. In the arrangement of the physical layer, its data volume directly has a key impact on the overall information transmission volume per unit time. In the case of unable to connect to the network, receiving satellite signals to obtain correction data has become the mainstream method. How to complete the transmission efficiently and quickly within the limited satellite transmission rate/time has become a top priority.

In the PPP-RTK joint positioning technology, the information is divided into three layers: SSR1, SSR2, and SSR3. Among them, SSR1 includes correction number categories: orbit -4068.2, clock offset -4068.3, code deviation -4068.4; SSR2 includes correction number categories: phase deviation -4068.5, global ionospheric correction number (VTEC); SSR3 includes correction number categories: Regional atmospheric correction number (1, regional ionospheric STEC-4068.8; 2.1, regional ionospheric residual RC-4068.9; 2.2, regional atmospheric correction Tropo-4068.9). The following table 3 shows the SSR format name and transmission interval information table broadcast by the satellite.

table 3

The traditional RTCM coding and the compact SSR coding of QZSS, the corresponding effective area (Network) is basically a range of 100km*100km, that is, 1 Network=10,000 square kilometers area. The encoding format is shown in Table 4.

Table 4

We can see that in traditional coding, for each visible satellite of each GNSS system (a total of GPS, GLONASS, Galileo, Beidou, QZSS, etc.), the corresponding four coefficients (C ₀₀ , C ₀₁ ,C ₁₀ ,C ₁₁ ). For each transmission, the traditional data volume of this information is 5,184,000 bits, which is calculated by the following formula (2) and formula (3):

6+14+12+12+10=54bits (2)

54*Number of GNSS systems(5)*Number of satellites involved in a single GNSS system (average 20)=54*5*20=5400bits (3)

Based on China’s 9.6 million square kilometers, the number of Networks is 960 (refer to the above-mentioned 100km*100km as the area of a single area), and the data volume of a single transmission of this message is: 5400*960=5,184,000 bits.

According to this calculation, the requirement for satellite communication resources (the rate is usually 1200bits to 2400bits per second) is extremely high, because the particularity of STEC information is that the data itself has a certain timeliness, and the longer the interval, the worse the correction effect. This application is mainly optimized for the 4068.8 regional ionospheric correction information in the above SSR3, which significantly improves the overall satellite positioning results.

Further, the physical meanings and usage methods of the four coefficients of the first, second, third and fourth model polynomial coefficients (ie C ₀₀ , C ₀₁ , C ₁₀ and C ₁₁ ) involved in each embodiment of the present application are as follows: As shown in 5, in a specific area (10,000 square kilometers as an example), different user terminals use the same set of model polynomial coefficients as input for terminal positioning correction, where φ in the table is the user’s observation latitude, and φ ₀ is The user's reference latitude, λ is the user's observation longitude, λ ₀ is the user's reference longitude, and δI _ai is the final STEC calculation value obtained by the user.

Among them, type 0 is the simplest, using the first coefficient to provide a correction number through a single point to correct the error. type 1 uses the first to third coefficients to provide correction numbers in a plane mode for plane correction. Type2 uses the first to fourth coefficients, and provides correction numbers in a two-dimensional plane to correct the plane. The technical solution of this application can be applied to either type 2 or type 3. The adjustment of the relevant method steps and system composition is included in the protection scope of one or more embodiments of this specification, and will not be repeated.

table 5

STEC Type Method notes 0 δI _ai = C ₀₀ 1 δI _ai = C ₀₀ + C ₀₁ (φ-φ ₀ ) + C ₁₀ (λ-λ ₀ )

2 δI _ai = C ₀₀ + C ₀₁ (φ-φ ₀ )+C ₁₀ (λ-λ ₀ )+C ₁₁ (φ-φ ₀ )(λ-λ ₀ ) 3 Keep

The reference pages are:

Page 1: http://www.rtcm.org/differential-global-navigation-satellite--dgnss--standards.html

Page 2: http://qzss.go.jp/en/technical/download/pdf/ps-is-qzss/is-qzss-l6-001.pdf

Page 3: http://qzss.go.jp/en/technical/download/pdf/ps-is-qzss/is-qzss-l6-001.pdf

Page 4: http://qzss.go.jp/en/technical/ps-is-qzss/ps-is-qzss.html

It should be noted that those skilled in the art should understand that the implementation functions of the modules shown in the implementation of the above-mentioned differential correction data transmission and/or reception system can refer to the correlation of the aforementioned differential correction data transmission and/or reception method. Describe and understand. The function of each module shown in the implementation of the system for transmitting and/or receiving differential correction data can be realized by a program (executable instruction) running on a processor, or by a specific logic circuit. If the aforementioned differential correction data sending and/or receiving system in the embodiment of the present application is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the embodiments of the present application essentially or the part that contributes to the prior art can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for A computer device (which may be a personal computer, a server, or a network device, etc.) executes all or part of the methods described in the various embodiments of the present application. The aforementioned storage media include: U disk, mobile hard disk, Read Only Memory (ROM, Read Only Memory), magnetic disk or optical disk and other media that can store program codes. In this way, the embodiments of the present application are not limited to any specific hardware and software combination.

Correspondingly, the embodiments of the present application also provide a computer-readable storage medium in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, the first, third, or second embodiments of the present application are implemented. Implementation of each method in five implementations. Computer-readable storage media include permanent and non-permanent, removable and non-removable media, and information storage can be realized by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, CD-ROM, digital versatile disc (DVD) or other optical storage, Magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media can be used to store information that can be accessed by computing devices. According to the definition in this article, computer-readable storage media does not include transitory media, such as modulated data signals and carrier waves.

In addition, the embodiment of the present application also provides a device for sending differential correction data, which includes a memory for storing computer-executable instructions, and a processor; the processor is used to implement the computer-executable instructions in the memory Steps in each method implementation in the first embodiment or the fifth embodiment described above. Among them, the processor can be a central processing unit (Central Processing Unit, "CPU"), other general-purpose processors, digital signal processors (Digital Signal Processor, "DSP"), and application specific integrated circuits (Application Specific Integrated Circuits). Integrated Circuit, referred to as "ASIC"), etc. The aforementioned memory may be a read-only memory (read-only memory, "ROM"), random access memory (random access memory, "RAM"), flash memory (Flash), hard disk or solid state hard disk, etc. The steps of the methods disclosed in the various embodiments of the present invention may be directly embodied as executed by a hardware processor, or executed by a combination of hardware and software modules in the processor.

In addition, the embodiment of the present application also provides a receiving device for differential correction data, which includes a memory for storing computer-executable instructions, and a processor; the processor is used to implement the computer-executable instructions in the memory The steps in each method implementation in the third embodiment described above. Among them, the processor can be a central processing unit (Central Processing Unit, "CPU"), other general-purpose processors, digital signal processors (Digital Signal Processor, "DSP"), and application specific integrated circuits (Application Specific Integrated Circuits). Integrated Circuit, referred to as "ASIC"), etc. The aforementioned memory may be a read-only memory (read-only memory, "ROM"), random access memory (random access memory, "RAM"), flash memory (Flash), hard disk or solid state hard disk, etc. The steps of the methods disclosed in the various embodiments of the present invention may be directly embodied as executed by a hardware processor, or executed by a combination of hardware and software modules in the processor.

It should be noted that in the application documents of this patent, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply these There is any such actual relationship or sequence between entities or operations. Moreover, the terms "include", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device that includes a series of elements includes not only those elements, but also includes Other elements of, or also include elements inherent to this process, method, article or equipment. If there are no more restrictions, the element defined by the phrase "including one" does not exclude the existence of other same elements in the process, method, article, or equipment including the element. In the application documents of this patent, if it is mentioned that an act is performed based on a certain element, it means that the act is performed at least based on that element, which includes two situations: performing the act only based on the element, and performing the act based on the element and Other elements perform the behavior. Multiple, multiple, multiple, etc. expressions include two, two, two, and two or more, two or more, and two or more expressions.

All documents mentioned in this application are considered to be included in the disclosure of this application as a whole, so that they can be used as a basis for modification when necessary. In addition, it should be understood that the above descriptions are only preferred embodiments of this specification, and are not intended to limit the protection scope of this specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of one or more embodiments of this specification shall be included in the protection scope of one or more embodiments of this specification.

Claims (21)

A method for sending differential correction data, the differential correction data including the first, second, third and fourth model polynomial coefficients of the oblique ionospheric correction algorithm model, characterized in that the sending method includes: The server obtains the range and resolution of ionospheric data in the current region; The server separately determines the bit length of at least one of the second, third, and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region; The server sends at least one of the second, third and fourth model polynomial coefficients to the user terminal according to the determined bit length. The method for sending differential correction data according to claim 1, wherein the server determines the second, third, and fourth model polynomial coefficients according to the range and resolution of the ionospheric data in the current region. The bit length of at least one of, further includes: The server determines a preset threshold range according to the resolution; If the ionospheric data range is within the preset threshold range, the bit length of at least one of the second, third and fourth model polynomial coefficients is the first bit length, otherwise it is the second bit length, where The first bit length is less than the second bit length. The method for sending differential correction data according to claim 1, wherein the server determines the second, third, and fourth model polynomial coefficients according to the range and resolution of the ionospheric data in the current region. The bit length of at least one of, further includes: The server separately determines the required bit length of at least one of the second, third and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region; The server separately determines whether the bit length of at least one of the second, third, and fourth model polynomial coefficients is the first bit length or the second bit length according to the required bit length. The method for sending differential correction data according to claim 1, wherein the server determines the second, third, and fourth model polynomial coefficients according to the range and resolution of the ionospheric data in the current region. Before the bit length of at least one of, it also includes: The server presets an expanded function data pointer, and the expanded function data pointer is used to switch at least one of the second, third, and fourth model polynomial coefficients between the first bit length and the second bit length. The method for transmitting differential correction data according to claim 4, wherein the expansion function data pointer is 3-bit binary data, wherein each bit indicates whether the second, third, and fourth model polynomial coefficients are The expansion function is enabled. A system for transmitting differential correction data, wherein the differential correction data includes the first, second, third, and fourth model polynomial coefficients of the oblique ionospheric correction algorithm model, which is characterized in that it includes: The acquisition module is used to acquire the ionospheric data range and resolution of the current region; A processing module for determining the bit length of at least one of the second, third, and fourth model polynomial coefficients according to the ionospheric data range and resolution of the current region; The sending module sends at least one of the second, third and fourth model polynomial coefficients to the user terminal according to the determined bit length. The differential correction data sending system according to claim 6, wherein the processing module is further configured to determine a preset threshold value range according to the resolution, and if the ionospheric data range is within the preset threshold value Within the range, the bit length of at least one of the second, third, and fourth model polynomial coefficients is the first bit length, otherwise it is the second bit length, wherein the first bit length is less than the second bit length. The system for transmitting differential correction data according to claim 6, wherein the processing module is further configured to determine the second, third, and first data according to the range and resolution of the ionospheric data in the current region. The required bit length of at least one of the four model polynomial coefficients, and the bit length of at least one of the second, third, and fourth model polynomial coefficients is the first bit length or the second bit length respectively determined according to the required bit length Bit length. 7. The differential correction data transmission system according to claim 6, wherein the processing module uses a preset expansion function data pointer to make the bits of at least one of the second, third and fourth model polynomial coefficients The length is switched between the first bit length and the second bit length. The differential correction data transmission system according to claim 9, wherein the expansion function data pointer is 3-bit binary data, wherein each bit indicates whether the second, third, and fourth model polynomial coefficients are The expansion function is enabled. A method for receiving differential correction data, characterized in that it comprises: The user terminal receives differential correction data from the server, where the differential correction data includes the first, second, third, and fourth model polynomial coefficients of the oblique ionospheric correction algorithm model; The user terminal separately determines the bit length of at least one of the second, third, and fourth model polynomial coefficients; The user terminal decodes at least one of the second, third and fourth model polynomial coefficients according to the determined bit length. The method for receiving differential correction data according to claim 11, wherein the user terminal separately determining the bit length of at least one of the second, third, and fourth model polynomial coefficients, further comprising: The user terminal determines that the bit length of at least one of the second, third, and fourth model polynomial coefficients is the first bit length or the second bit length; If it is the first bit length, decode at least one of the second, third and fourth model polynomial coefficients according to the first bit length; If it is the second bit length, decode at least one of the second, third and fourth model polynomial coefficients according to the second bit length. The method for receiving differential correction data according to claim 11, wherein the differential correction data further comprises a preset expansion function data pointer, and the expansion function data pointer is used to enable the second, third, and At least one of the fourth model polynomial coefficients is switched between the first bit length and the second bit length; The user terminal separately determining the bit length of at least one of the second, third and fourth model polynomial coefficients further includes: The user terminal determines whether the bit length of at least one of the second, third, and fourth model polynomial coefficients is the first bit length or the second bit length according to the preset expansion function data pointer. The method for receiving differential correction data according to claim 13, wherein the expansion function data pointer is 3-bit binary data, wherein each bit indicates whether the second, third, and fourth model polynomial coefficients are The expansion function is enabled. A device for transmitting differential correction data, characterized in that it comprises: Memory for storing computer executable instructions; and, The processor is configured to implement the steps in the method according to claim 1 when the computer-executable instructions are executed. A method for transmitting differentially corrected data, the differentially corrected data includes first, second, and third model polynomial coefficients of an oblique ionospheric correction algorithm model, characterized in that the transmitting method includes: The server obtains the range and resolution of ionospheric data in the current region; The server separately determines the bit length of at least one of the second and third model polynomial coefficients according to the ionospheric data range and resolution of the current region; The server sends at least one of the second and third model polynomial coefficients to the user terminal according to the determined bit length. The method for sending differential correction data according to claim 16, wherein the server separately determines at least one of the second and third model polynomial coefficients according to the range and resolution of the ionospheric data in the current region The bit length of further includes: The server determines a preset threshold range according to the resolution; If the ionospheric data range is within the preset threshold range, the bit length of at least one of the second and third model polynomial coefficients is the first bit length, otherwise it is the second bit length. The length of one bit is less than the length of the second bit. The method for sending differential correction data according to claim 16, wherein the server separately determines at least one of the second and third model polynomial coefficients according to the range and resolution of the ionospheric data in the current region The bit length of further includes: The server separately determines the required bit length of at least one of the second and third model polynomial coefficients according to the ionospheric data range and resolution of the current region; The server separately determines whether the bit length of at least one of the second and third model polynomial coefficients is the first bit length or the second bit length according to the required bit length. The method for sending differential correction data according to claim 16, wherein the server separately determines at least one of the second and third model polynomial coefficients according to the range and resolution of the ionospheric data in the current region Before the bit length, it also includes: The server presets an expanded function data pointer, and the expanded function data pointer is used to switch at least one of the second and third model polynomial coefficients between the first bit length and the second bit length. The method for transmitting differential correction data according to claim 19, wherein the expansion function data pointer is 2-bit binary data, wherein each bit indicates whether expansion is enabled for the second and third model polynomial coefficients. Features. A device for transmitting differential correction data, characterized in that it comprises: Memory for storing computer executable instructions; and, The processor is configured to implement the steps in the method according to claim 16 when the computer executable instructions are executed.

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