CN103197327B - Method and system for updating global position system (GPS) ephemeris fast and reliably - Google Patents

Abstract

The invention relates to a method and system for quickly and reliably updating GPS ephemeris. The system sets up a local GPS ephemeris server. The local GPS ephemeris server has a built-in virtual GPS ephemeris generation module. Under normal circumstances, the local GPS ephemeris server obtains ephemeris data from the official GPS ephemeris server. When the local GPS ephemeris server is disconnected from the GPS official ephemeris server, the virtual GPS ephemeris generation module starts to work to generate accurate virtual ephemeris, and the GPS ephemeris data of the local GPS ephemeris server will immediately switch to the internal virtual ephemeris GPS ephemeris data to ensure the continuity and reliability of GPS ephemeris data. It can help each A-GPS terminal host to significantly shorten the TTFF time (time to first fix after power-on). Therefore, the time for the first positioning after the cold start of the A-GPS terminal positioning system can be shortened to within 20 seconds, realizing fast and reliable positioning.

Description

A method and system for quickly and reliably updating GPS ephemeris

technical field

The invention relates to a method and system for quickly and reliably updating GPS ephemeris.

Background technique

When the application of GPS continues to promote personal portable applications, the traditional GPS positioning method has a considerable bottleneck in its use. A stand-alone GPS device that uses autonomous positioning (Autonomous Positioning) must receive more than four satellite signals in an open sky with good signal conditions, and the GPS receiver of this device must also complete the orbit information data of these GPS satellites. Collect all, and then the positioning calculation can be performed.

The start-up and positioning time of the GPS receiver after it is turned on for the first time depends on the way of start-up. Generally, it can be divided into three types: cold start, warm start and hot start:

Cold Start: The GPS receiver has cleared all historical data, or the GPS receiver has moved more than 1000km without power on, the GPS receiver will try to locate and lock the satellite, because the historical data has been cleared, it will need to a long time. GPS receivers use a method similar to polling to lock on to signals from all the satellites, which is much slower than knowing in advance which satellites to search for. This type of lock reacquisition takes a very long time. Depending on the GPS module used, the time to reacquire the lock can vary from a few minutes to an hour.

Warm Start: GPS saves the last calculated satellite position, almanac and UTC time, but the saved content is not the current visible satellite data. After restarting, the GPS will try to obtain the current satellites and signals and calculate its new position. GPS can make an approximate guess at the current visible satellites in the sky based on its last position and almanac.

Hot Start: GPS saves the last calculated visible satellite position, almanac (almanac) and UTC time. After restarting, GPS obtains and calculates the latest position of the current satellite based on the above saved content, which can be Rapid positioning.

For portable navigation applications, due to the existence of cold start, the time to first fix (TTFF) of autonomous positioning after power-on is too long, and users are often in streets with many buildings, under viaducts, or even Especially in the indoor environment, due to the poor signal reception conditions in these places, it takes a long time for the user to wait for the first positioning, and it may not be successful.

In this case, for a single A-GPS terminal host, the fastest way to start positioning is hot start, and the assisted positioning method of obtaining satellite information through another network turns cold start into hot start, that is, A-GPS (Aiding GPS), has become an inevitable trend in the development of GPS. In response to this situation, there are currently two different forms of A-GPS solutions on the market to help users shorten TTFF time and quickly realize positioning.

One is the online A-GPS method (AssistNow Online), which obtains real-time satellite information through mobile communication systems such as GSM, GPRS, CDMA or UMTS in real time. The other is to use the offline A-GPS method (AssistNow offline), download satellite data in advance through the mobile network or directly from the Internet, and can play the role of auxiliary positioning when needed. The A-GPS involved in the present invention is an online A-GPS.

The traditional online A-GPS mobile terminal generally communicates with the traditional standard ephemeris server (or the server's mirror (Mirror) or proxy (Proxy) ephemeris server) through the TCP/IP protocol to obtain GPS Auxiliary satellite positioning data required for positioning. The ephemeris data on the traditional ephemeris server is generally obtained from the GPS official ephemeris server, that is, the so-called GPS root ephemeris server. The validity period of the ephemeris data is only a few hours. When the traditional ephemeris server is disconnected from the GPS root ephemeris server, each A-GPS terminal host can not obtain the latest GPS ephemeris and cannot perform fast positioning.

Contents of the invention

Aiming at the deficiencies of the prior art, the invention proposes a solution for fast and reliable updating of A-GPS ephemeris. Help each A-GPS terminal host to obtain the latest high-precision virtual GPS ephemeris from the local GPS ephemeris server even if the local GPS ephemeris server cannot directly obtain the latest GPS ephemeris from the GPS root ephemeris server, To help users shorten the TTFF time and quickly achieve positioning. Therefore, the time for the first positioning after the cold start of the A-GPS terminal host positioning system can be shortened to within 20 seconds.

The technical scheme that the present invention solves technical problem to take is:

A system for quickly and reliably updating GPS ephemeris includes multiple A-GPS terminal hosts and a local GPS ephemeris server. The local GPS ephemeris server includes a virtual GPS ephemeris generation module inside. The virtual GPS ephemeris generation module is a GPS ephemeris prediction module running on the local GPS ephemeris server. The prediction module uses historical GPS ephemeris data, combined with the operating characteristics of satellites, and uses the algorithm of differential ephemeris correction data to predict the satellite trajectory in the next few hours and generate more accurate satellite ephemeris data.

Each A-GPS terminal host accesses the local GPS ephemeris server on the Internet through GPRS or WIFI connection to obtain the latest GPS ephemeris data.

The method for updating the GPS ephemeris by using the above system includes two processes, namely, the A-GPS terminal host obtains the GPS ephemeris from the local GPS ephemeris server; the local GPS ephemeris server obtains the ephemeris from the GPS root ephemeris server. the

The A-GPS terminal host obtains the GPS ephemeris process from the local GPS ephemeris server, and the steps include:

101: The A-GPS terminal host is powered on, and each part of the system is initialized.

102: Judging whether it is necessary to update the satellite ephemeris in the GPS module, if it is not necessary to update, then perform step 107, and if it needs to be updated, then perform step 103.

103: Determine whether the GSM/GPRS or WIFI of the terminal has connected to the Internet. If connected to the Internet, step 104 is performed, and if not connected to the Internet, step 107 is performed.

104: After the terminal is connected to the Internet, it will connect to the local GPS ephemeris server, and perform step 105 after confirming that the connection is correct.

105: Download the latest GPS ephemeris data from the local GPS ephemeris server to the A-GPS terminal host, and execute step 106 after completion.

106: After the A-GPS terminal host obtains the latest GPS ephemeris, it converts the ephemeris data into a unified internal ephemeris format recognizable by the GPS module, and then uses the ephemeris update command of the GPS module to update the ephemeris data to A-GPS terminal host. Execute step 107 after completion.

107: The system will wait for the A-GPS terminal host to locate until the positioning ends and the A-GPS terminal host ephemeris update process ends.

(2) The process that the local GPS ephemeris server obtains the ephemeris from the GPS root ephemeris server, and the steps include:

201: The local GPS ephemeris server connects to the GPS root ephemeris server every 2 seconds, and when the timing reaches 2 seconds, execute step 202.

202: The local GPS ephemeris server will first try to connect to the preferred first GPS root ephemeris server in the list, if not, go to step 203. If it can be connected, go to step 206.

203: Try to connect to the second backup GPS root ephemeris server, if not, go to step 204. If you can connect, go to step 206.

204: Try to connect to the third backup GPS root ephemeris server, if not, go to step 205. If you can connect, go to step 206.

205: Try to connect to the nth standby GPS root ephemeris server, if the connection cannot be made, the system will jump out of the connection task and go to step 206, if it can be connected, also go to step 206.

206: The local GPS ephemeris server will judge whether it can communicate with the above-mentioned multiple GPS root ephemeris servers, if it can communicate normally, execute step 208, if not, notify the system that the connection to the GPS root ephemeris server fails. Execute step 207.

207: The system will start the virtual GPS ephemeris module, obtain accurate GPS ephemeris through the previously obtained GPS ephemeris data and the algorithm of correcting the data according to the differential ephemeris, and execute step 210 after completion.

208: After the connection between the local GPS ephemeris server and the (3,4,5,7) GPS root ephemeris server is established, the system will query whether the GPS root ephemeris server has GPS ephemeris data that can be updated. When the system detects that new ephemeris data is generated, step 209 is executed. If no newly updated data is detected, the data update ends, and the next data update process is waited for, and step 201 is executed.

209: Start the ephemeris data downloading program, and completely download the new ephemeris data to the local GPS ephemeris server.

210: After the local GPS ephemeris server obtains new GPS ephemeris data from the GPS root ephemeris server or the virtual GPS ephemeris generation module, it will convert the data into an ephemeris array that the GPS module can recognize, and save it to the local GPS In the ephemeris server, wait for the A-GPS terminal host to read, execute step 201, and proceed to the next cycle.

The A-GPS terminal host updates the GPS ephemeris data to the A-GPS terminal host by using the GPS ephemeris update command, and converts the cold start process of the system into a hot start.

The present invention can assist each A-GPS terminal host, and when the local GPS ephemeris server loses connection with the GPS root ephemeris server and cannot obtain the latest GPS ephemeris from the GPS root ephemeris server, it can also realize fast positioning and help Each A-GPS terminal host shortens the TTFF time (the first positioning time after power-on).

Description of drawings

Figure 1. Block diagram of GPS ephemeris data update system;

Figure 2. The process of updating the A-GPS terminal host ephemeris from the local GPS ephemeris server;

Figure 3. The local GPS ephemeris server obtains the GPS root ephemeris server ephemeris process.

Detailed ways

The specific embodiment of the present invention is described below in conjunction with accompanying drawing

Figure 1 is a block diagram of the GPS ephemeris data update system. The GPS ephemeris updating system actually includes an A-GPS terminal host 6 and a local GPS ephemeris server 2 . There can be many A-GPS terminal hosts, and there is only one local GPS ephemeris server. The local GPS ephemeris server contains a virtual GPS ephemeris generation module 1 inside. The local GPS ephemeris server is connected to the Internet, and obtains the latest ephemeris data from each GPS root ephemeris server3,4,5,7. When the local GPS ephemeris server is disconnected from each GPS root ephemeris server, the internal ephemeris data source will immediately switch to the internal virtual GPS ephemeris generation module. The virtual GPS ephemeris generation module can use the differential almanac correction data (Differential Almanac Correction Data) algorithm based on the previously obtained satellite ephemeris when the local GPS ephemeris server is temporarily disconnected from the GPS root ephemeris server. Calculate the more accurate satellite ephemeris data for the next few hours, or even dozens of hours, to generate a high-precision virtual GPS ephemeris. This virtual satellite ephemeris data can be run independently from the GPS root ephemeris server, and the validity period can reach 5 days in extreme cases.

So as to ensure that the system can provide GPS ephemeris data stably and reliably. Each A-GPS terminal host automatically selects GPRS or WIFI to connect to the local GPS ephemeris server to download the latest ephemeris according to the current network connection. Access the local GPS ephemeris server to obtain the latest GPS ephemeris data, thus speeding up the first GPS positioning process.

The local GPS ephemeris server is set up on the Internet, and the ephemeris data has two sources, one data comes from the GPS official ephemeris server, such as the IGS global reference network, which is the so-called GPS root ephemeris server3,4,5 ,7. The other one is a virtual GPS ephemeris generating module built into the local GPS ephemeris server.

Generally, the local GPS ephemeris server obtains the ephemeris data in real time from the GPS official ephemeris server, ensuring that the data of the local GPS ephemeris server and the data of the GPS official ephemeris server are updated synchronously in real time. When the local GPS ephemeris server is disconnected from the GPS official ephemeris server for some reason, the GPS ephemeris data of the local GPS ephemeris server will immediately switch to virtual GPS ephemeris data to ensure the continuity of GPS ephemeris data and reliability.

The data of the virtual GPS ephemeris is obtained from the built-in virtual GPS ephemeris generation module of the local GPS ephemeris server. It can provide up to 5 days of ephemeris data from the local GPS ephemeris server until the connection with the GPS official GPS root ephemeris server is restored.

Fig. 2 obtains the GPS ephemeris process from the local GPS ephemeris server for the A-GPS terminal host, and the steps include:

101: The A-GPS terminal host is powered on, and each part of the system is initialized.

102: Judging whether it is necessary to update the satellite ephemeris in the GPS module, if it is not necessary to update, then perform step 107, and if it needs to be updated, then perform step 103.

103: Determine whether the GSM/GPRS or WIFI of the terminal has connected to the Internet. If connected to the Internet, step 104 is performed, and if not connected to the Internet, step 107 is performed.

104: After the terminal is connected to the Internet, it will connect to the local GPS ephemeris server, and perform step 105 after confirming that the connection is correct.

105: Download the latest GPS ephemeris data from (2) the local GPS ephemeris server to (6) the A-GPS terminal host, and execute step 106 after completion.

106: (6) After obtaining the latest GPS ephemeris, the A-GPS terminal host converts the ephemeris data into a unified internal ephemeris format recognizable by the GPS module, and then uses the ephemeris update command of the GPS module to update the ephemeris The data is updated to (6) A-GPS terminal host. Execute step 107 after completion.

107: The system will wait for (6) A-GPS terminal host positioning until the end of positioning, and (6) A-GPS terminal host ephemeris update process ends.

Fig. 3 obtains the ephemeris process from the (3,4,5,7) GPS root ephemeris server for the local GPS ephemeris server, and the steps include:

201: The local GPS ephemeris server connects to the GPS root ephemeris server every 2 seconds, and when the timing reaches 2 seconds, execute step 202.

202: The local GPS ephemeris server will first try to connect to the preferred GPS root ephemeris server 3 in the list, if not, go to step 203. If it can be connected, go to step 206.

203: Try to connect to the second backup GPS root ephemeris server 4, if not, go to step 204. If it can be connected, go to step 206.

204: Try to connect to the third standby GPS root ephemeris server 5, if it cannot be connected, go to step 205. If it can be connected, go to step 206.

205: Try to connect to the nth standby GPS root ephemeris server 7, if the connection cannot be made, the system will jump out of the connection task and go to step 206, if it can connect, also go to step 206.

206: The local GPS ephemeris server will judge whether it can communicate with the GPS root ephemeris server. If it can communicate normally, execute step 208. If not, notify the system that the connection to the GPS root ephemeris server fails. Execute step 207.

207: The system will start the virtual GPS ephemeris module, obtain accurate GPS ephemeris through the previously obtained GPS ephemeris data and the algorithm of correcting the data according to the differential ephemeris, and execute step 210 after completion.

208: After the connection between the local GPS ephemeris server and the GPS root ephemeris server is established, the system will query whether the GPS root ephemeris server has GPS ephemeris data that can be updated. When the system detects that new ephemeris data is generated, step 209 is executed. If no newly updated data is detected, the data update ends, and the next data update process is waited for, and step 201 is executed.

209: Start the ephemeris data downloading program, and completely download the new ephemeris data to the local GPS ephemeris server.

210: After the local GPS ephemeris server obtains new GPS ephemeris data from the GPS root ephemeris server or the virtual GPS ephemeris generation module, it will convert the data into an ephemeris array that the GPS module can recognize, and save it to the local GPS In the ephemeris server, wait for the A-GPS terminal host to read, execute step 201, and proceed to the next cycle.

In the relevant step 207, (1) the course of work of the virtual GPS ephemeris generating module:

The virtual GPS ephemeris generation module is a GPS ephemeris prediction software running on the local GPS ephemeris server. The software uses historical GPS ephemeris data, combined with the operating characteristics of satellites, and uses the Algorithm of Differential Almanac Correction Data to predict the satellite trajectory in the next few hours and generate more accurate satellite ephemeris data.

The virtual ephemeris generated by software inference can maintain valid ephemeris for several hours or even tens of hours, so that accurate ephemeris data can be obtained even when the local GPS ephemeris server and the GPS root ephemeris server are disconnected.

There are two types of ephemeris data that the A-GPS terminal host obtains from the local GPS ephemeris server and imports into the GPS module, Almanac and Ephemeris. The Chinese name is generally translated as broadcast ephemeris and precise almanac:

Almanac (broadcast ephemeris) data is a relatively rough orbital parameter that reflects the status of all satellites. Each satellite will broadcast the Almanac data of all satellites. This type of data is relatively imprecise and valid for several months.

Ephemeris (precise almanac) data is in contrast very accurate orbit and clock correction information, each satellite will only broadcast its own Ephemeris data, this type of data is valid for about a few hours (depending on the broadcast information contains content). Ephemeris data is updated every 15 minutes on average and broadcast every 30 seconds.

In relevant step 210, the conversion method of ephemeris data:

The preferred server for ephemeris data acquisition is the IGS Global Reference Network. The original Almanac ephemeris data obtained from IGS, the ephemeris data of the first 6 GPS satellites are annotated as follows:

Satellite internal number 1 2 3 4 5 6 satellite health 0 0 0 0 0 0 Satellite track eccentricity 0.001639 0.012144 0.016019 0.010332 0.003056 0.007832 square root of semimajor axis 5153.7 5153.6 5153.6 5153.7 5153.5 5153.6 ascending node right ascension -4.868 -6.01 -72.959 -5.063 54.98 -68.438 Argument of perigee 20.957 -151.82 72.983 55.239 18.166 -21.355 mean anomaly 25.452 74.835 84.277 -99.559 -165.526 -168.155 almanac moment 61440 61440 61440 61440 61440 61440 Up to 54 degree dip offset 1.0451 -0.1861 -0.516 -0.241 0.378 -0.1305 Equatorial I velocity -0.00044 -0.00045 -0.00049 -0.00045 -0.00047 -0.00049 satellite clock 0 0 0 0 0 0 satellite clock drift 0 0 0 0 0 0 GPS week 1731 1731 1731 1731 1731 1731

These data are the key data used to describe the orbit of GPS satellites.

According to the original Almanac data of the satellite, the trajectory of the GPS satellite in the next few hours, or even dozens of hours, can be predicted.

Visibility predictions for GPS satellites for the next 24 hours are available based on the satellite's raw Almanac data.

By using the GPS ephemeris update command to update the above Almanac data to the A-GPS terminal host, the cold start process of the system will be converted into a hot start, which can greatly shorten the time for the first boot.

Furthermore, the Ephemeris (precise almanac) of GPS satellites can be updated to the A-GPS terminal host, which will further speed up the process of satellite positioning and locking for the first boot, and shorten the time for the first boot. the

The following is the part of the GPS satellite Ephemeris (accurate almanac) obtained from the (3,4,5,7) GPS root ephemeris server at 0:30 am on March 10, 2013

* 2013 3 10 0 30 0.00000000

PG01 -4238.806870 -14648.089913 -21767.768287 6.213531 9 10 9 185

PG02 -18430.600125 14005.325091 12734.023677 421.665203 7 7 9 185

PG03 8769.176587 -23998.363421 6301.471878 178.490494 8 6 8 170

PG04 -25956.152269 6264.296321 643.565173 156.746189 5 8 10 196

PG05 -6176.671099 15283.380947 20766.453950 -387.151521 10 6 7 215

PG06 13593.297005 -19504.175506 11565.689192 321.106033 8 6 6 197

PG07 -19608.594128 -7471.019306 16496.136938 189.380853 6 6 7 195

PG08 -25738.017560 -2100.714400 7523.575627 5.034836 8 10 8 188

GPS satellite ephemeris data format conversion,

The ephemeris data obtained from the GPS root ephemeris server is an ephemeris forecast file current.alm in Yuma format. current.alm is a file in plain text txt format, which clearly describes the current Almanac data of each satellite.

Almanac data consists of 448 16-bit signed data, representing the relative status of 32 different satellites, 14 data per satellite.

The actual effective data of Almanac data is 896 bytes, and its validity period can be as long as several months.

In the local GPS ephemeris server, the data of the ephemeris file needs to be converted into a format that the system can recognize.

Let's take the ephemeris data of the third satellite in the current.alm file as an example:

********* Week 707 almanac for PRN-03 ***********

ID: 03

Health: 000

Eccentricity: 0.1602125168E-001

Time of Applicability(s): 147456.0000

Orbital Inclination(rad): 0.9334536747

Rate of Right Ascen(r/s): -0.8617501811E-008

SQRT(A) (m 1/2): 5153.613281

Right Ascen at Week(rad): -0.1274126090E+001

Argument of Perigee(rad): 1.273876294

Mean Anom(rad): 0.1450665333E+001

Af0(s): 0.1792907715E-003

Af1(s/s): 0.3637978807E-011

week: 707

Convert these ephemeris data in text form to the IRN-200D-001 standard.

Taking the data of the third satellite as an example, the converted data contains a message body with a length of 30 (0x1E) bytes, and the reply number is 0x0E, which is Almanac data. The satellite data of No. 0x03 is: 97 C1....BB 3A, the last few digits are check codes.

A0 A2 00 1E 0E 03 97 C1 43 73 78 63 F6 BD FD 22 00 A1 0C B9 CB 69 6D 2C 0F 4D 46 B3 D8 5C 00 23 BB E4 0D 4A B0 B3

The converted data will be saved to the local GPS ephemeris server, waiting for the A-GPS terminal host to read. After the A-GPS terminal host obtains these data, it executes the 0x82 command to write the current Almanac data into the GPS module in binary form, and waits for the GPS module to lock the satellite and quickly locate it.

Claims (2)

1. fast and reliable upgrades a method for GPS ephemeris, and the system used comprises multiple A-GPS end host (6) and a local GPS ephemeris server (2); Described local GPS ephemeris server (2), inside comprises a virtual GPS ephemeris generation module (1); Described virtual GPS ephemeris generation module (1) is the GPS ephemeris prediction module that local GPS ephemeris server runs; GPS ephemeris prediction module uses history GPS almanac data, in conjunction with the operation characteristic of satellite, is inferred the satellite transit track of next several hours by the algorithm of difference ephemeris correction data, generates comparatively accurate satellite almanac data; Each A-GPS end host (6) is by the connected mode of GPRS or WIFI, local GPS ephemeris server (2) on access internet, obtain up-to-date GPS almanac data, its feature comprises A-GPS end host (6) in the method and obtains GPS ephemeris from local GPS ephemeris server (2), local GPS ephemeris server (2) is from GPS root ephemeris server (3,4,5,7) ephemeris is obtained, two processes:

(1) A-GPS end host (6) obtains GPS ephemeris process from local GPS ephemeris server (2), and step comprises:

101:A-GPS end host (6) powers on, and carries out initialization to system components;

102: judge whether to need to upgrade the satellite ephemeris in GPS module, just perform step 107 if do not need to upgrade, if need to upgrade, just perform step 103;

103: judge whether GSM/GPRS or WIFI of terminal has accessed internet; If be connected to internet just perform step 104, if be not connected to internet just perform step 107;

104: local GPS ephemeris server (2) can be connected to after terminal accessing Internet, after determining exact connect ion, perform step 105;

105: download up-to-date GPS almanac data to A-GPS end host (6) from local GPS ephemeris server (2), execution step 106 after completing;

After 106:A-GPS end host (6) obtains up-to-date GPS ephemeris, almanac data is converted to the discernible inner ephemeris format of unified GPS module, re-use the ephemeris more newer command of GPS module, almanac data is updated to A-GPS end host (6); Execution step 107 after completing;

107: system can wait for A-GPS end host location (6), until location is terminated, A-GPS end host (6) ephemeris renewal process terminates;

(2) local GPS ephemeris server obtains the process of ephemeris from GPS root ephemeris server (3,4,5,7), and step comprises:

201: local GPS ephemeris server (2) connected a GPS root ephemeris server (3,4,5,7) at interval of 2 seconds, when timing reaches 2 seconds, perform step 202;

202: first local GPS ephemeris server (2) can attempt connecting first-selected GPS root ephemeris server (3) in list, if can not connect, performs step 203; If can connect, perform step 206;

203: attempt connection second GPS root ephemeris for subsequent use server (4), if can not connect, just perform step 204; If can connect, perform step 206;

204: attempt connection the 3rd GPS root ephemeris server (5) for subsequent use, if can not connect, perform step 205; Step 206 is performed if can connect;

205: attempt connection n-th GPS root for subsequent use ephemeris server (7), if can not connect, system will jump out connection task, perform step 206, if can connect, also perform step 206;

206: local GPS ephemeris server (2) can judge whether can with GPS root ephemeris server (3,4,5,7) communication is carried out, if can normal communication, perform step 208, if can not communication, notice system obtains GPS root ephemeris server (3,4,5,7) connection failure; Perform step 207;

207: system can start virtual GPS ephemeris production module, by the GPS almanac data obtained before, according to the algorithm of difference ephemeris correction data, obtain accurate GPS ephemeris, execution step 210 after completing;

208: after local GPS ephemeris server (2) and GPS root ephemeris server (3,4,5,7) connect, whether system can inquire about GPS root ephemeris server (3,4,5,7) the GPS almanac data that can upgrade; When systems axiol-ogy is to when having new almanac data to generate, perform step 209, if the new data upgraded do not detected, Data Update terminates, and waits for next data updating process, performs step 201;

209: enable almanac data and download, download to local GPS ephemeris server (2) by complete for new almanac data;

210: local GPS ephemeris server (2) is from GPS root ephemeris server (3,4,5,7) or after virtual GPS ephemeris generation module (1) obtains new GPS almanac data, data can be changed, convert the ephemeris array that GPS module can identify to, be saved in local GPS ephemeris server (2), wait for that A-GPS end host (6) reads, perform step 201, carry out next one circulation.

2. method according to claim 1, it is characterized in that: A-GPS end host (6) is by using the more newer command of GPS ephemeris, GPS almanac data is updated to A-GPS end host (6), converts the Cold Start of system to warm start.