CN113933865A

CN113933865A - Method, device, computer storage medium and terminal for realizing coding processing

Info

Publication number: CN113933865A
Application number: CN202111106114.0A
Authority: CN
Inventors: 赵旎; 陈孔哲; 周光宇; 高静波
Original assignee: Zhendian Technology Beijing Co ltd
Current assignee: Zhendian Technology Beijing Co ltd
Priority date: 2021-09-22
Filing date: 2021-09-22
Publication date: 2022-01-14

Abstract

Disclosed herein are a method, an apparatus, a computer storage medium and a terminal for implementing encoding processing, including: the receiver respectively calculates the total coding length of observed values which can be coded in the same multi-signal message (MSM) in the epoch; encoding observations encodable on the same MSM on more than one MSM according to the determined total encoding length and a marine radio technology Committee (RCTM) message limit length; wherein, the observed values that can be encoded in the same MSM include: observations of all frequency points from the same satellite navigation system. After the total coding length of the observation values which can be coded in the same MSM in the epoch is calculated, the MSM coding observation values with the length limited to more than one according to the determined total coding length and the RCTM message are calculated, so that the coding and decoding difficulty of the observation values and the complexity of message synchronization are reduced while the number of the MSMs is reduced, and the bandwidth utilization rate is improved.

Description

Method, device, computer storage medium and terminal for realizing coding processing

Technical Field

The present disclosure relates to, but not limited to, coding techniques, and more particularly, to a method, an apparatus, a computer storage medium, and a terminal for implementing coding.

Background

At present, there are five widely used Global Navigation Satellite Systems (GNSS) in the world, which are the Global Positioning System (GPS) in the united states, the GLONASS (GLONASS) in russia, the beidou satellite navigation system (BDS) in china, the Galileo satellite navigation system (Galileo) in the european union, and the quasi-zenith satellite system (QZSS) in japan; the satellite navigation positioning system has high precision and covers the whole world, and is widely applied to the fields of navigation, measurement and mapping, fine agriculture, intelligent robots, unmanned driving, unmanned aerial vehicles and the like. The main factors influencing the satellite positioning accuracy are satellite orbit errors, clock error errors and atmospheric propagation errors. The satellite orbit error and the clock error calculated in real time through the broadcast ephemeris are generally in the meter level, for example, the broadcast ephemeris precision of the GPS is 1-2 meters, and the GLONASS broadcast ephemeris precision is several meters. The atmospheric propagation errors mainly comprise ionosphere errors and troposphere errors, the ionosphere errors can reach dozens of meters for a low-elevation satellite in noon time, the ionosphere errors can be eliminated by a double-frequency receiver through a double-frequency observation value, the troposphere delay can reach 10 meters for the low-elevation satellite, and 90% of the troposphere errors can be eliminated through a troposphere model. Under the condition of no correction number, the high-performance double-frequency receiver can also achieve meter-level positioning accuracy.

For applications requiring centimeter-level positioning accuracy such as surveying and mapping, fine agriculture, intelligent robots, unmanned vehicles and unmanned aerial vehicles, real-time differential positioning (RTK) is mainly adopted for error processing. RTKs can be divided into single station RTKs and network RTKs; the international maritime committee 104 promulgated a standard protocol RTCM STANDARD 104, abbreviated RTCM protocol, for solving the compatibility problem of differential data between different brands of receivers, and the latest version of RTCM is RTCM3.3(RTCM STANDARD 10403.3, 2016).

The compatibility problem of differential data among receivers of different brands is solved by the RTCM protocol, and the RTK protocol is widely introduced in RTK application; especially, the multi-Signal Message (MSM) newly added in the latest version of RTCM3.3 can encode the multi-system multi-frequency point observed value tracked by the receiver; the MSM introduces a satellite, signal and observation value mask mechanism, and only encodes the observation values tracked by the receiver, so that the MSM can encode the observation values tracked by all satellites to the same frequency point and also encode the observation values different in the tracking frequency points of different satellites. The observation values of the satellites are divided into rough observation values and fine observation values, the observation values (tens of thousands of kilometers) of one satellite are only different by dozens of meters, the rough observation values shared by the observation values are extracted and uniformly coded, and each observation value is only coded relative to the difference value part of the rough observation values, so that the coding length can be reduced. MSM is the most widely used differential data format in RTK applications.

According to different application requirements, the RTCM designs seven MSMs of MSM1-MSM 7. Each MSM consists of a message header, satellite data and signal data; wherein, the message header is the information common to all the satellite corrections of a satellite system. The field definitions of the message headers of MSM1-MSM7 are the same, table 1 is an exemplary table of the message headers of MSM, and as shown in table 1, the message headers include message numbers, base station displacement Identifiers (IDs), epoch times, satellite masks, signal masks and other fields and field lengths; the MSM satellite data part comprises information common to all tracking signals of a satellite, such as approximate pseudorange and Doppler observed value; the signal data part of the MSM contains information such as accurate pseudorange, carrier, Doppler and carrier-to-noise ratio of some signals of a satellite.

TABLE 1

The satellite data part and the signal data part of the MSM1-MSM7 are different in coding information, and a user can select a proper coding type according to an application scene; table 2 is a table of information compositions of MSM1-MSM7, as shown in table 2, MSM1-MSM7 encoding contents and the length of each satellite data part and respective signal data part; the MSM is used to encode observations of the receiver, which may be used for Differential Global Navigation Satellite System (DGNSS)/RTK applications or for saving observations as post-processing; among them, MSM1 is mainly used for DGNSS application; MSM 2-MSM 4 are mainly used for RTK applications; MSM5 and MSM7 are used primarily to store all observations compatible with receiver independent interchange formats (rint) for post-processing; the MSM6 encodes the complete pseudorange, carrier observation value and carrier-to-noise ratio information with higher resolution, is mainly used for transmitting physical base station data in network RTK application, is used for network RTK resolving to generate virtual base station correction, and the generated virtual base station correction is generally encoded by the MSM 4. In RTK applications, MSM4 is the most commonly used type of coding because MSM4 contains the full pseudoranges, carrier observations, and carrier-to-noise ratios, which are just all the information of the base station needed for RTK solution, and the resolution also meets the requirements of RTK.

TABLE 2

Currently, five satellite navigation systems, namely a GPS, a BDS, a GLONASS, a Galileo and a QZSS, are widely used for RTK application; the encoding mechanism of MSM is that each observation of the satellite navigation system is encoded with more than one MSM, so that an observation of one epoch may be encoded by multiple MSMs. MSMs of all satellite navigation systems of the same epoch realize synchronization through a 'message synchronization code' field in a message header, and when the message synchronization code field in one MSM is 1, the MSM observation value of the subsequent homoepoch is shown to arrive; when the message synchronization code field of one MSM is 0, the MSM is the last group of observed values of the epoch; only after receiving the last set of observations can the rover station decode all the observations of the base station for RTK solution.

In the RTCM3.3 standard, there are two limitations for MSM: 1. the length of MSM can not exceed the limited length of RCTM message, and the limited length of RCTM message is 1023 bytes (byte, 8184bit) at present, that is 1023 bytes is the maximum length of all MSM allowed by RTCM; 2. the observation mask for MSM cannot exceed 64 bits; MSM limits the observation mask length to ensure that a single MSM is no longer than 1023 bytes long. If a satellite navigation system provides 4 satellite signals, the 64-bit observation mask can encode 64/4 ═ 16 satellite observations at most, even if MSM7 message with the highest resolution of encoded content is used, and the length is: 169+64+16 + 36+16 + 4+ 80-5929 (bits), the length limit of 8184 bits is far from being reached. When the RTCM3.3 standard is promulgated, the GPS system with the most satellites in five satellite navigation systems is only 32, the BDS is only 14 satellites, the number of Galileo satellites is less than 20, the GLONASS is only 24 satellites, and the QZSS is only 4 satellites; a receiver at any position on the earth can track no more than 16 satellites of a single satellite navigation system, and the satellite signal type of each satellite is no more than 4, so that the observation mask length required for encoding all the observations of one satellite navigation system is less than 16 × 4-64; even if the observation mask has a 64-bit limit, one MSM is sufficient to encode all observations of one satellite navigation system. With the building and the opening of the Beidou No. three system, the Beidou satellite navigation system has 44 in-orbit satellites for providing navigation service, more than 25 satellites can be tracked by a receiver in most of domestic time, and up to 30 satellites can be tracked in some time periods. When the MSM codes the observation value of the Beidou system, the signal mask is at least 5 bits, and under the protection of the length of the 64-bit observation value mask, one MSM can code the observation value of at most 12 Beidou satellites (12 × 5 is 60); if the observation values of 25 Beidou satellites need to be coded, three MSMs are needed, the first two of the MSMs code the observation values of 12 satellites, and the second one codes the observation values of 1 satellite; therefore, the difficulty of coding and decoding is increased, and the complexity of message synchronization and the required transmission bandwidth are also increased; how to encode and realize the MSM which is easier and more applicable becomes a problem to be solved in the application of the satellite navigation system.

Disclosure of Invention

The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

Embodiments of the present invention provide a method, an apparatus, a computer storage medium, and a terminal for implementing encoding processing, which can reduce encoding and decoding difficulty of an observed value and complexity of message synchronization, and improve bandwidth utilization.

The embodiment of the invention provides a method for realizing coding processing, which comprises the following steps:

the receiver respectively calculates the total coding length of the observed values which can be coded in the same multi-signal message MSM in the epoch;

encoding observations that can be encoded in the same MSM on more than one MSM according to the determined total encoding length and the defined length of the maritime radio technology Committee RCTM message;

wherein the observation values that can be encoded in the same MSM include: observations of all frequency points from the same satellite navigation system.

On the other hand, the embodiment of the present invention further provides a computer storage medium, in which a computer program is stored, and the computer program, when executed by a processor, implements the above method for implementing encoding processing.

In another aspect, an embodiment of the present invention further provides a terminal, including: a memory and a processor, the memory having a computer program stored therein; wherein,

the processor is configured to execute the computer program in the memory;

the computer program, when executed by the processor, implements a method of implementing encoding processing as described above.

In another aspect, an embodiment of the present invention further provides an apparatus for implementing encoding processing, where the apparatus includes: a calculation unit and an encoding processing unit; wherein,

the calculation unit is configured to: respectively calculating the total coding length of observed values which can be coded in the same multi-signal message MSM in the epoch;

the encoding processing unit is configured to: encoding observations that can be encoded in the same MSM on more than one MSM according to the determined total encoding length and the defined length of the maritime radio technology Committee RCTM message;

The technical scheme of the application includes: the receiver respectively calculates the total coding length of observed values which can be coded in the same multi-signal message (MSM) in the epoch; encoding observations encodable on the same MSM on more than one MSM according to the determined total encoding length and a marine radio technology Committee (RCTM) message limit length; wherein, the observed values that can be encoded in the same MSM include: observations of all frequency points from the same satellite navigation system. After the total coding length of the observation values which can be coded in the same MSM in the epoch is calculated, the MSM coding observation values with the length limited to more than one according to the determined total coding length and the RCTM message are calculated, so that the coding and decoding difficulty of the observation values and the complexity of message synchronization are reduced while the number of the MSMs is reduced, and the bandwidth utilization rate is improved.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the example serve to explain the principles of the invention and not to limit the invention.

FIG. 1 is a flow chart of a method for implementing an encoding process according to an embodiment of the present invention;

fig. 2 is a block diagram of an apparatus for implementing encoding processing according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.

The steps illustrated in the flow charts of the figures may be performed in a computer system such as a set of computer-executable instructions. Also, while a logical order is shown in the flow diagrams, in some cases, the steps shown or described may be performed in an order different than here.

The inventor of the present application has analyzed and found that: to make the MSM length no longer than 1023 bytes, RTCM3.3 limits the length of the observation mask. This limitation causes some satellite navigation system observations to require multiple MSMs to encode, and the length of each MSM is far from the upper limit of 1023 bytes. The message headers of the three MSMs of the Beidou satellite are basically repeated, and if the three MSMs can be coded into one MSM and the limitation of the RTCM on the message length of 1023 bytes is not exceeded, the bandwidth is saved, and the coding and decoding complexity can be reduced. Although the Beidou navigation system provides five civil navigation signals, no satellite broadcasts five satellite signals at the same time; the second Beidou system satellite transmits three civil navigation signals: B1I, B2I and B3I. the Beidou No. three system non-geographic position (GEO) satellite transmits four civil navigation signals: B1I, B3I, B1a and B2a, wherein the GEO satellite in the Beidou III system transmits two civil navigation signals: B1I, B3I; the different satellite signals cause waste on the mask of the observed value; because the Beidou satellite observation values have 5 satellite signals in total, 5 bits in the signal masks (32 bits) are 1, and therefore each satellite needs to occupy 5-bit observation value masks, under the limit of the length of 64-bit observation value masks, one MSM can only encode the observation values of 12 Beidou satellites (12 × 5 equals to 60). Although each satellite occupies 5 bits of observation value mask, each satellite can track 4 kinds of satellite signals at most, while the satellite of the Beidou second system only has 3 kinds of satellite signals, and the GEO satellite of the Beidou third system only has 2 kinds of satellite signals; if there are 6 satellites of the big dipper No. two system (each satellite tracks three satellite signals and corresponds to 3 observation values) and 6 non-GEO satellites of the big dipper No. three system (each satellite tracks four satellite signals and corresponds to 4 observation values) in the 12 satellites encoded by the group of MSM4, the length of the group of MSM4 is: 169+60+12 + 18+48 (6 × 3+6 × 4) 2461 (bit); the length of the message header is 169+60 (60 bits are observation value masks), the code of the shared data part of each satellite needs 18 bits, the satellite data of 12 satellites occupies 12 x 18, the length of the observation value part is 48 x (6 x 3+6 x 4), the complete data part of each observation value occupies 48 bits, the total number of the observation values is 6 x 3+6 x 4, the satellites of 6 Beidou No. two systems, and each satellite has 3 observation values; 6 Beidou third system satellites and 4 observation values for each satellite. This set of MSM4 is quite different from the RTCM message length limit 8184bit (1023 bytes), though it is full observation mask length (60 bits), but the entire message length is 2461 (bits); encoding realizes simple and applicable MSM, and becomes a problem to be solved by application of a satellite navigation system.

Fig. 1 is a flowchart of a method for implementing encoding processing according to an embodiment of the present invention, as shown in fig. 1, including:

step 101, the receiver respectively calculates the total coding length of the observed values which can be coded in the same multi-signal message (MSM) in the epoch; wherein, the observed values that can be encoded in the same MSM include: observations of all frequency points from the same satellite navigation system.

The epoch in the embodiment of the present invention is an absolute time concept, for example, the sampling rate is 15 seconds, which means that a set of satellite observation data is acquired every 15 seconds, and 15 seconds is called an epoch.

Step 102, encoding observation values which can be encoded in the same MSM on more than one MSM according to the determined total encoding length and the limited length of the navigation radio technology committee (RCTM) message.

After the total coding length of the observation values which can be coded in the same MSM in the epoch is calculated, the MSM coding observation values with the length limited to more than one according to the determined total coding length and the RCTM message are calculated, so that the coding and decoding difficulty of the observation values and the complexity of message synchronization are reduced while the number of the MSMs is reduced, and the bandwidth utilization rate is improved.

In one illustrative example, an embodiment of the present invention calculates a total encoded length of observations within an epoch that are encodable on the same MSM, comprising:

respectively calculating the lengths of a message header, satellite data and signal data in the MSM if the observed values are coded in the same MSM;

and accumulating the lengths of the message header, the satellite data and the signal data obtained by calculation to obtain the total coding length.

It should be noted that the lengths of the message header, the satellite data and the signal data may be calculated with reference to the encoding rule of the RCTM protocol. In the embodiment of the invention, the observation values which can be coded in the same MSM are respectively calculated to obtain the corresponding total coding length so as to be used for determining that the observation values which can be coded in the same MSM are coded on a plurality of MSMs.

In one illustrative example, an embodiment of the invention encodes observations that can be encoded on the same MSM onto more than one MSM, comprising:

when the total coding length is less than or equal to the limited length of the RCTM message, coding the observed value on a MSM;

when the total coding length is greater than the limited length of the RCTM message, splitting the observed value into more than two observed value subsets according to a preset strategy; respectively encoding each observation value subset obtained by splitting on a MSM; wherein, the total coding length of the observation values contained in the observation value subset satisfies: less than or equal to the RCTM message defined length.

When the total coding length is less than or equal to the RCTM message limited length, the observation values are coded on one MSM, and compared with the condition that the relative technology is limited by the observation value mask length, the method and the device for coding the observation values code all the observation values in one MSM and are not influenced by the observation value mask length while the MSM length is prevented from exceeding the RCTM message limited length.

In an exemplary embodiment, splitting an observation value into more than two observation value subsets according to a preset policy includes:

and according to the appearance sequence of the satellite signals corresponding to the observed values in the satellite mask, taking the limited length of the RCTM message as the split unit length, and splitting the observed values into more than two observed value subsets.

When the total coding length is greater than the RCTM message limited length, the RCTM message limited length is used as the splitting unit length, the observed value in one epoch is split and coded on more than two MSMs, and compared with the condition that the related technology is limited by the mask length of the observed value, the method and the device provided by the embodiment of the invention avoid the MSM length exceeding the RCTM message limited length, and simultaneously code the observed values in each MSM as much as possible. The number of MSM codes is reduced; referring to the relevant processing of encoding and decoding, the encoding and decoding difficulty of the observed value and the complexity of message synchronization are reduced based on the reduction of the number of MSMs in the embodiment of the invention.

In an exemplary embodiment, when the observation is encoded into more than one MSM, the method of the embodiments of the present invention further includes:

when the observation value is coded on one MSM, setting the message synchronization code field of the coded MSM to be 0;

and when each observation value subset obtained by splitting is respectively coded on one MSM, and the coded MSM is not the last MSM, setting the message synchronization code of the MSM to be 1, and when the coded MSM is the last MSM, setting the message synchronization code of the MSM to be 0.

The embodiment of the invention realizes the identification of whether the observed value which can be coded in the same MSM completes coding or not through the message synchronous coding, and provides information support for determining the decoding process and continuously executing the subsequent processing.

The embodiment of the invention also provides a computer storage medium, wherein a computer program is stored in the computer storage medium, and when being executed by a processor, the computer program realizes the method for realizing the coding processing.

An embodiment of the present invention further provides a terminal, including: a memory and a processor, the memory having stored therein a computer program; wherein,

the processor is configured to execute the computer program in the memory;

the computer program, when executed by a processor, implements a method of implementing an encoding process as described above.

Fig. 2 is a block diagram of an apparatus for implementing encoding processing according to an embodiment of the present invention, as shown in fig. 2, including: a calculation unit and an encoding processing unit; wherein,

wherein, the observed values that can be encoded in the same MSM include: observations of all frequency points from the same satellite navigation system.

In an illustrative example, the computing unit in the embodiment of the present invention is configured to:

In an exemplary embodiment, the encoding processing unit in the embodiment of the present invention is configured to:

In an exemplary example, an encoding processing unit according to an embodiment of the present invention is configured to split an observation value into two or more observation value subsets according to a preset policy, and includes:

In an exemplary embodiment, the encoding processing unit of the embodiment of the present invention is further configured to:

The following is a brief description of the embodiments of the present invention by way of application examples, which are only used to illustrate the embodiments of the present invention and are not used to limit the scope of the present invention.

Application example

On the premise of meeting the limit length of the RTCM message, the application example cancels the mask limit of the observation value in the MSM, and the observation value of each satellite navigation system is coded in one MSM as much as possible; the MSM number is reduced by one epoch (an epoch is an absolute time concept, for example, a sampling rate is 15 seconds, which means that a set of satellite observation data is acquired every 15 seconds, and 15 seconds are referred to as an epoch), so that the encoding and decoding complexity is reduced, and the bandwidth can also be reduced.

According to the application example, after an observation value acquired in one epoch of a receiver is subjected to observation, the observation values of all satellite navigation systems are distinguished; when the receiver codes the observation value in one epoch, each MSM can only code the observation value of one satellite navigation system, if the receiver acquires the observation values of five satellite navigation systems including BDS, GPS, GLONASS, Galileo and QZSS, at least 5 MSMs need to be coded, when the observation values of each satellite navigation system are coded, the coding type needs to be determined, namely, the type of the MSM1-MSM7 is determined; the present application example refers to the correlation principle to encode the MSM for the observed values of different encoding types.

The present application example takes MSM4 as an example to illustrate the encoding flow of observed values, and MSM4 is the most widely applied encoding type in RTK. The encoding takes a satellite navigation system as an order, the MSM of one satellite navigation system is encoded, the MSM of the next satellite navigation system is encoded, one epoch only has the 'message synchronization code' field of the last MSM as 0, and the 'message synchronization code' fields of all MSMs encoded in the front are all set as 1; the encoding of observations of the BDS satellite navigation system with message type MSM4 is illustrated below:

determining the number of tracked satellites and the number of observation values output by each satellite for the acquired satellite observation data of one epoch; taking the BDS as an example, the receiver determines the number of satellites tracked by the current epoch and the number of observed values output by each satellite; whether the observed value can be coded in one MSM4 is determined according to the number of the tracked satellites and the number of the observed values output by each satellite.

Suppose that 25 satellites are tracked by the BDS; wherein 12 Beidou second system satellites and 13 Beidou third system satellites; the Beidou satellite navigation system has observed values of 5 satellite signals: B1I, B2I, B3I, B1c and B2 a; in one epoch, the satellite of each big dipper system two outputs 3 observations: B1I, B2I and B3I; the satellite of each big dipper No. three system outputs 4 observed values: B1I, B1c, B2a, B3I; the observed values for the 25 satellites total 3 × 12+4 × 13-88 (bit). According to the number of the tracked satellites and the number of the observation values output by each satellite, the signal mask length can be determined: 25 × 5 ═ 125 (bit). MSM4 thus has a header length of 169+125 ═ 294 (bit); and the satellite data length is: 25 × 18 ═ 450 (bit); the signal data length is: 88 × 48 ═ 4224 (bit). If the observed values of the 25 Beidou satellites are coded in one MSM4, the total coding length is as follows: 294+450+4224 ═ 4968(bit), the application determines that observations can be encoded in a single MSM4 by determining that the total encoded length does not exceed the length defined by the 1023byte (8184bit) RTCM message.

In the encoding process, the application example firstly encodes an MSM4 message header according to the satellite signal of the current epoch; encoding a satellite mask according to Pseudo Random Noise (PRN) numbers of 25 satellites; encoding a signal mask according to 5 kinds of satellite signals B1I, B2I, B3I, B1c, B2a (civil navigation signals); encoding an observation mask according to the sequence of the 25 satellite signals appearing in the satellite mask and the type of each satellite signal; if a satellite of a certain Beidou No. two system has 3 observation values, namely B1I, B2I and B3I, the mask positions corresponding to B1I, B2I and B3I in a 5-bit observation value mask are 1, and the mask positions corresponding to other two signals B1c and B2a are 0; the encoding of the MSM described above in this application example is performed with reference to the relevant standard. Next, according to the sequence of the 25 satellite signals appearing in the satellite mask, the satellite data part and the signal data part are coded; and after the encoding is finished, calculating the check code of the whole MSM4 and filling the check code. The encoding of the various parts (including the message synchronization code) of the present application example is the same as the relevant standard. In an illustrative example, the present application example sets the "message synchronization code" field of the last MSM4 to a value of 0.

The present application example encodes observations of other satellite navigation systems with reference to the above-described processing.

If the MSM6 with higher resolution is adopted, the method can also verify that one MSM6 can encode 25 Beidou satellites; the rest of MSM6 is the same as MSM4, except that the data portion of the signal is of higher resolution, occupying 65 bits of each signal. The signal data portion length of MSM6 is: 88 x 65 ═ 5720 (bit); if the observed values of 25 Beidou satellites are coded in one MSM6, the total coding length is as follows: 294+450+5720 6464(bit), which does not exceed the length limit of the 1023byte (8184bit) RTCM message, can be encoded in a single MSM 6.

If encoding is carried out according to the rule that the mask of the observation value is less than or equal to 64, for the Beidou satellites with 5 satellite signals, each MSM can only encode the observation value of 12 Beidou satellites. The observed values of 25 Beidou satellites require 3 MSMs to encode. Not only does the encoding require splitting the observations of the satellites of one system into different MSMs, but the encoding length is also increased because the message headers of multiple MSMs of one system are identical. Two MSM headers (169bit) and two RTCM headers (24bit) and check codes (24bit) are wasted, totaling (169+24+24) × 2-434 (bit). Approximately 8.7% of the length (4968bit) encoded by 1 MSM4, and 8.7% of the bandwidth can be saved by encoding MSM4 according to the new encoding rule.

Table 3 shows the encoding length of the MSM of 25 beidou satellites under the observation mask length mechanism without being limited by this application example; as can be seen from table 3, the MSM1-MSM6 does not limit the observation mask, the observation can be encoded into an MSM, and the lengths of MSM1-MSM6 do not exceed the length defined by the RTCM message, which can save the bandwidth by more than 6%.

MSM type	Encoding Length (bit) of this application example MSM	Saving bandwidth ratio
			MSM1	1864	23.3％
MSM2	2920	14.9％
			MSM3	4240	10.2％
MSM4	4968	8.7％
			MSM5	6738	6.4％
MSM6	6464	6.7％

TABLE 3

If MSM7 is used for encoding, which is also 25 beidou satellites, the length of the MSM7 header part is 169+25 × 5 ═ 294 (bit). And the satellite data part length is: 25 × 36 ═ 900 (bit). The signal data portion length is: 88 × 80 ═ 7040 (bit). If the observed values of 25 Beidou satellites are coded in one MSM7, the total coding length is as follows: 294+900+7040 8234(bit), beyond the RTCM message limit length of 8184bit, the observations of 25 beidou satellites can only be encoded in two MSMs 7; even so, the present application example is less complex than when three MSMs 7 are needed to limit the observation mask length. The embodiment of the invention reduces the complexity reduction of encoding and decoding caused by the number of encoding strips, if a plurality of MSMs exist, the message synchronization code of the last MSM is set to be 0, if three MSMs exist, after the first MSM and the second MSM are decoded, the system waits for the third MSM, when the decoding determines that the message synchronization code is 0, the system determines that the decoding of all satellite correction numbers of the current epoch is finished, the correction numbers obtained by decoding can be used, and if the message synchronization code is not set, the system can be caused to keep waiting for the next MSM and can not finish the decoding.

Judging the number of MSM-capable encoding satellites according to the encoding type of the MSM and the number of observation values contained in a satellite of a satellite navigation system; when the length of all observation value codes of a satellite navigation system in one MSM does not exceed 1023 bytes, canceling the limitation of the mask length of the observation value, and coding the observation values of all satellites of the satellite navigation system in one MSM; when the length of all satellite codes in one MSM exceeds 1023 bytes, the maximum satellite number which can be coded by 1023 bytes is calculated, the observed value of the maximum satellite number is coded in one MSM, and the observed values of the rest satellites are coded in another MSM. This application example modifies the 64-bit observation mask length limit in the RTCM MSM, subject to the standard RTCM message 1023byte length limit. Satellites which need multiple MSMs to be coded under the condition of an observation value mask length limit of 64 bits are coded in one MSM. MSM coding information number is reduced, bandwidth is saved, and coding and decoding complexity is reduced. The above analysis can show that: on the premise of meeting the limit of the RTCM limited length, the embodiment of the invention cancels the limit of the observed value mask, modifies the MSM observed value mask rule under the condition of following the limit of 1023 bytes of the RTCM, and codes the observed values of all satellites of the Beidou system of the receiver in one MSM, thereby saving the bandwidth and reducing the complexity of coding and decoding.

"one of ordinary skill in the art will appreciate that all or some of the steps of the methods, systems, functional modules/units in the devices disclosed above may be implemented as software, firmware, hardware, and suitable combinations thereof. In a hardware implementation, the division between functional modules/units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component may have multiple functions, or one function or step may be performed by several physical components in cooperation. Some or all of the components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on computer readable media, which may include computer storage media (or non-transitory media) and communication media (or transitory media). The term computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, as is well known to those of ordinary skill in the art. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by a computer. In addition, communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media "as is well known to those of ordinary skill in the art.

Claims

1. A method of implementing an encoding process, comprising:

2. The method of claim 1, wherein said calculating a total encoded length of observations in epochs that are encodable in the same MSM comprises:

calculating the observation values which can be coded in the same MSM in the epoch, and respectively calculating the lengths of a message header, satellite data and signal data in the MSM if the observation values are coded in the same MSM;

3. The method of claim 1 or 2, wherein encoding observations encodable on the same MSM onto more than one MSM comprises:

when the total coding length is less than or equal to the RCTM message limited length, the observation value is coded on a MSM;

when the total coding length is greater than the limited length of the RCTM message, splitting the observation value into more than two observation value subsets according to a preset strategy; respectively encoding each observation value subset obtained by splitting on a MSM; wherein, the total coding length of the observation values contained in the observation value subset satisfies: less than or equal to the RCTM message defined length.

4. The method of claim 3, wherein splitting the observations into more than two subsets of observations according to a predetermined policy comprises:

and splitting the observation values into more than two observation value subsets by taking the limited length of the RCTM message as the split unit length according to the appearance sequence of the satellite signals corresponding to the observation values in the satellite mask.

5. The method of claim 3, wherein when encoding observations into more than one MSM, the method further comprises:

and when each observation value subset obtained by splitting is respectively coded on one MSM and the coded MSM is not the last MSM, setting the message synchronization code of the MSM to be 1, and when the coded MSM is the last MSM, setting the message synchronization code of the MSM to be 0.

6. A computer storage medium having stored thereon a computer program which, when executed by a processor, implements a method of implementing an encoding process as claimed in any one of claims 1 to 5.

7. A terminal, comprising: a memory and a processor, the memory having a computer program stored therein; wherein,

the processor is configured to execute the computer program in the memory;

the computer program, when executed by the processor, implements a method of implementing an encoding process as claimed in any one of claims 1 to 5.

8. An apparatus for implementing an encoding process, comprising: a calculation unit and an encoding processing unit; wherein,

9. The apparatus of claim 8, wherein the computing unit is configured to:

10. The apparatus according to claim 8 or 9, wherein the encoding processing unit is configured to: