CN101275997B - Software GPS receiver tracking method based on equal length CA code - Google Patents

Abstract

A method for tracking a software GPS receiver of an equal-length CA code comprises the following procedures: generating a searching table of CA code with equal length; reading the equal-length C/A code corresponding with the code phase; adopting a two-stage integration integral method for calculating the numerical value of I and Q branch line of early code, instantaneous code and late code and avoiding a jump deflection of integration crossing the navigation text data; comparing the data symbol of two accumulated fragments to determine whether the jump deflection of the navigation text data exists; using the above six numbers in two stages for calculating the new carrier frequency, carrier phase and code phase, and setting the data jump deflection with floating point type for modifying the code phase drift caused by Doppler frequency shift; and determining whether the floating point type jump deflection can cross the integer, and in this way the navigation text drifting caused by Doppler frequency shift can be modified through a re-synchronization mechanism. The invention simplifies the calculation and saves time and space, and at the same time the jump deflection point and tracking loop error are eliminated.

Description

A kind of software GPS receiver tracking method based on equal length CA code

Technical field

The present invention relates to software GPS receiver tracking method, especially relate to a kind of method of following the tracks of based on the software GPS receiver of equal length CA code.

Background technology

The develop rapidly of satellite navigation technology has replaced conventional navigation techniques such as radio navigation, celestial navigation gradually, and becomes a kind of navigator fix technology that generally adopts, and has obtained rapid progress at precision, real-time, aspect such as round-the-clock.At present, the global positioning system of moving in the world mainly contains two big systems: the one, and GPS of USA system, the 2nd, Muscovite GLONASS (Ge Lunasi) system.In recent years, Europe has also proposed to have " Galileo " global positioning satellite plan of own characteristic.Thereby the Global Positioning System (GPS) at space of gathering future will form the situation that GPS, " Ge Lunasi ", " Galileo " three big systems that the United States, Russia, Europe handle compete.

The tracking of GPS receiver is one of most crucial algorithm of GPS receiver.Traditional GPS receiver tracking method as shown in Figure 1, (1) obtains the carrier frequency and the code phase information of last registration; (2) read the carrier wave of corresponding carrier frequency and carrier phase; (3) the CA sign indicating number of readout code phase place correspondence; (4) adopt correlation-integral method, calculate early sign indicating number, instantaneous code and the I of late sign indicating number, 6 numerical value of Q branch road; (5) use above-mentioned 6 numerical value to carry out loop filtering, calculate new carrier frequency, carrier phase and code phase, and seek data saltus step position; (6) move other task scheduling (as acquiring satellite and positioning calculation); (7) arrival of the next data block of wait.

Because the influence of Doppler frequency skew, the CA sign indicating number of GPS receiver general equal life cycle in tracking, referring to Borre, K., D.Akos, D.Bertelsen, P.Rinder and S.Jensen, " A Software-DefinedGPS and Galileo Receiver-A Single Frequency Approach "

Boston, 2006.P.147.But in software receiver system, wait the CA sign indicating number in cycle to generate a large amount of extra times or the space that may take the software processes device, cause the complicacy of software algorithm, reach the prolongation of time and take a large amount of spaces.

Summary of the invention

Technology of the present invention is dealt with problems: overcome the deficiencies in the prior art, a kind of software GPS receiver tracking method based on equal length CA code is proposed, this method uses equal length CA code to follow the tracks of, and makes computing become simple and saves time and the space, has eliminated trip point and track loop error simultaneously.

Technical solution of the present invention: a kind of software GPS receiver tracking method of equal length CA code may further comprise the steps:

(1) obtains the carrier frequency and the code phase information of last registration;

(2), read the carrier data of corresponding carrier frequency and carrier phase in the carrier wave look-up table according to the carrier frequency obtained;

(3) according to the code phase information of obtaining, dynamically produce isometric C/A sign indicating number look-up table, with the complexity that reduces to search;

(4), read isometric C/A sign indicating number corresponding in the described isometric C/A sign indicating number look-up table according to code phase information;

(5) adopt two sections integration methods, to gps signal, I and two carrier data of Q branch road that receive, and the isometric C/A sign indicating number that is read carries out I, Q branch road early sign indicating number, instantaneous code and late sign indicating number integration, obtain 12 integration numerical value behind two sections integrations altogether, avoided integration to cross over navigation message data saltus step position like this;

(6) symbol to the integration numerical value of the I branch road of the I branch road of first section instantaneous code and second section instantaneous code compares, and judges whether to exist navigation message data saltus step position;

(7) if there is the data saltus step position of navigation message, then two sections integration numerical value that step (5) is obtained subtract each other, the if there is no data saltus step position of navigation message, and then two sections integration numerical value addition that step (5) is obtained obtains totally 6 integration numerical value;

(8) adopt described 6 integration numerical value to carry out loop filtering, calculate new carrier frequency, carrier phase and code phase, set the data saltus step position of floating type simultaneously, represent that with integral part the periodicity of data bit, fraction part represent the code phase that drifts about; Adopt new carrier frequency, carrier phase and code phase correction because the code phase drift that Doppler shift causes;

(9) judge whether floating type data saltus step position crosses over integer, if the code phase drift of crossing over integer then existing Doppler shift to cause, by heavy synchronous amending method, revise because the navigation message drift that Doppler shift causes has been revised the back and waited for next data block; If do not cross over integer, next data block is waited in the code phase drift that does not then exist Doppler shift to cause.

Two sections integrations are according to code phase information in the described step (5), and sampled signal is decomposed into former and later two sampling section at the code phase place.

The method of judging the data saltus step position that has navigation message in the described step (6) is: if two numerical symbols are identical, then there is not the data saltus step position of navigation message in explanation; If then there is the data saltus step position of navigation message in two numerical symbol differences;

Heavy sync correcting method in the described step (9) is:

(1) the CA sign indicating number cycle according to GPS is Mms, and the navigation message frequency is DHz, and continuous 1 or continuously-1 number is n=1000/M/D in the navigation message;

(2) when the floating-point part of the navigation message data of floating-point counting when forward passes through 0, continuous 1 or continuously-1 number is n+1 in the navigation message, for guaranteeing in the navigation message that continuous 1 or continuously-1 number is n, when floating type data saltus step position forward is crossed over integer, the saltus step bit position is moved one forward;

(3) when the floating-point part of the navigation message data of floating-point counting when oppositely passing through 0, continuous 1 or continuously-1 number may be n-1 in the navigation message, for guaranteeing in the navigation message that continuous 1 or continuously-1 number is n, when integer is oppositely crossed in floating type data saltus step position, the saltus step bit position is moved one backward.

The present invention's advantage compared with prior art is:

(1) according to GPS C/A sign indicating number standard, set up the CA sign indicating number look-up table of equal length, the bit rate of CA sign indicating number and length are not subjected to satellite Doppler's influence in look-up table, and bit rate remains 1.023MHz, and code length remains 1 millisecond.So just make the GPS software receiver internal memory look-up table size of carrier wave and C/A sign indicating number can be compressed in about the 5M byte usually, the software receiver of this architecture can be applied in the limited universal PC of internal memory, general dsp and the special DSP platform, make computing become simple and save time and the space.

(2) use the isometric GPS C/A sign indicating number that produces to carry out the tracking computing of GPS software receiver, because integration may be crossed over trip point, the present invention adopts the method for segmentation correlation integral to calculate to digital sampled data, at every turn the sample sampled data and the C/A of equal length of correlator carries out related operation, ignore the influence of doppler phenomenon, eliminated trip point and track loop error.

(3) as above-mentioned step (5), sampled signal is decomposed into two sampling segments at the code phase place, two segments are carried out twice correlation integral computing with the C/A sign indicating number that is produced respectively, be divided into integral result before the trip point and trip point after two integral results, thereby avoid integration to cross over the data bit trip point, eliminated trip point and track loop error.

(4) use the isometric GPS C/A sign indicating number that produces to carry out the tracking computing of GPS software receiver, ignored because the code phase drift that Doppler shift causes by the bit trip point being adopted non-integer recording mode, can be revised this code phase drift.In the floating-point representation of saltus step position, integral part is represented the periodicity of data bit, and fraction part is represented the code phase that drifts about.

(5), revise owing to ignore the navigation message drift that the Doppler frequency skew causes by heavy synchronization mechanism.When the saltus step position of record forward was crossed over integer or oppositely crossed over integer, trip point also changed thereupon, came the influence of correcting code phase drift to navigation message by revising integrating meter numerical value.

Description of drawings

Fig. 1 is traditional GPS intermediate-freuqncy signal tracking processing flow chart;

Fig. 2 is a tracking processing flow chart of the present invention;

Fig. 3 is traditional synoptic diagram such as sign indicating number such as cycle C/A such as grade;

Fig. 4 is an isometric C/A sign indicating number synoptic diagram of the present invention;

Fig. 5 for isometric C/A sign indicating number of the present invention and etc. the error synoptic diagram that exists between the cycle C/A sign indicating number;

Fig. 6 is a subsection integral synoptic diagram of the present invention;

Whether Fig. 7 crosses over the integer synoptic diagram for floating type saltus step of the present invention position.

Embodiment

The data of handling among the present invention are GPS digital intermediate frequency signals, and this signal carries out the down coversion post-sampling by the GPS radiofrequency signal by hardware and obtains.The sample frequency of digital medium-frequency signal must meet over-sampling or bandpass sampling law, and normal conditions are greater than 5MHz.Letter Signal Processing in the numeral is based on data block carries out, promptly from acquisition system or file system, obtains the sampled data (for example sampled data of 32 milliseconds) of some at every turn.Usually, the GPS software receiver can carry out following processing for each sampled data that enters the passage of Satellite Tracking, and as shown in Figure 2, concrete steps of the present invention are as follows:

(1) obtains the carrier frequency and the code phase information of last registration;

(2), read the carrier data of corresponding carrier frequency and carrier phase in the carrier wave look-up table according to the carrier frequency obtained.

(3) according to the code phase information of obtaining, dynamically produce isometric C/A sign indicating number look-up table, with the complexity that reduces to search.

According to GPS C/A sign indicating number standard, its sequence length is 1023 (number of chips).Because the spreading rate of CA sign indicating number is 1.023MHz, so the repetition period of pseudo-random sequence is 1ms.Here, produce the CA sign indicating number that isometric CA sign indicating number replaces complete cycle, the method that specifically generates is referring to ICD200c.Deng cycle C/A sign indicating number, as shown in Figure 3, constantly different, the C/A code length of different satellite correspondences has nothing in common with each other, thereby causes the huge complicacy of software algorithm in the software receiver.As shown in Figure 4, the present invention sets up the CA sign indicating number look-up table of equal length, and the bit rate of CA sign indicating number and length are not subjected to satellite Doppler's influence in look-up table, and bit rate remains 1.023MHz, and code length remains 1 millisecond.So just make the GPS software receiver internal memory look-up table size of carrier wave and C/A sign indicating number can be compressed in about the 5M byte usually, the software receiver of this architecture can be applied in the limited universal PC of internal memory, general dsp and the special DSP platform.

(4), read isometric C/A sign indicating number corresponding in the described isometric C/A sign indicating number look-up table according to code phase information;

(5) adopt two sections integration methods, to gps signal, I and two carrier data of Q branch road that receive, and the isometric C/A sign indicating number that is read carries out I, Q branch road early sign indicating number, instantaneous code and late sign indicating number integration, obtain 12 integration numerical value behind two sections integrations altogether, avoided integration to cross over navigation message data saltus step position like this.

As shown in Figure 5 because isometric C/A sign indicating number and etc. the error that exists between the cycle C/A sign indicating number, may there be the problem that does not line up with the C/A sign indicating number in sampled signal.According to Theoretical Calculation, the loss of signal that this problem may cause approximately is 0.014dB (Doppler is less than 10KHz).The present invention adopts the subsection integral method, will write down this error always, after this error accumulation to one chip, just carries out corresponding code phase adjustment; Be accumulated to above 1 C/A sign indicating number cycle, just carry out corresponding navigation text saltus step position adjustment, cross over navigation message data trip point to avoid integration.As shown in Figure 6, sampled signal is decomposed into former and later two sampling section at the code phase place, carries out relevant accumulating operation with the C/A sign indicating number respectively.Symbol difference according to two sections integral results can be predicted navigation message data trip point, thereby avoid integration to cross over trip point.For avoiding the influence of noise, calculate sign indicating number morning, instantaneous code and the I of late sign indicating number, two parts of Q branch road accumulation result and be stored in respectively in the navigation message of different time, thereby the result who guarantees elimination algorithm is not vulnerable to The noise the summation sign position.

For two sections integration methods, the concrete calculation procedure of 12 integration numerical value is as follows:

$I_{\mathrm{<figure-callout\; id="1"\; label="E"\; filenames="S2008101046011E00031.png,S2008101046011E00042.png"\; state="\{\{state\}\}">E</figure-callout>}1}=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;}+\mathrm{\&Delta;})\cos (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

$I_{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="S2008101046011E00031.png,S2008101046011E00042.png"\; state="\{\{state\}\}">P</figure-callout>}1}=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;})\cos (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

$I_{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="S2008101046011E00031.png,S2008101046011E00042.png"\; state="\{\{state\}\}">L</figure-callout>}1}=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;}-\mathrm{\&Delta;})\cos (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

$I_{\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="S2008101046011E00031.png"\; state="\{\{state\}\}">E</figure-callout>}2}=\underset{i=M}{\overset{N}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;}+\mathrm{\&Delta;})\cos (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

$I_{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="S2008101046011E00031.png"\; state="\{\{state\}\}">P</figure-callout>}2}=\underset{i=M}{\overset{N}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;})\cos (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

$I_{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="S2008101046011E00031.png"\; state="\{\{state\}\}">L</figure-callout>}2}=\underset{i=M}{\overset{N}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;}-\mathrm{\&Delta;})\cos (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

${\mathrm{<figure-callout\; id="1"\; label="Q\; E"\; filenames="S2008101046011E00031.png,S2008101046011E00042.png"\; state="\{\{state\}\}">Q</figure-callout>}}_E=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;}+\mathrm{\&Delta;})\sin (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

${\mathrm{<figure-callout\; id="1"\; label="Q\; P"\; filenames="S2008101046011E00031.png,S2008101046011E00042.png"\; state="\{\{state\}\}">Q</figure-callout>}}_P=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;})\sin (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

${\mathrm{<figure-callout\; id="1"\; label="Q\; L"\; filenames="S2008101046011E00031.png,S2008101046011E00042.png"\; state="\{\{state\}\}">Q</figure-callout>}}_L=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;}-\mathrm{\&Delta;})\sin (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

${\mathrm{<figure-callout\; id="2"\; label="Q\; E"\; filenames="S2008101046011E00031.png"\; state="\{\{state\}\}">Q</figure-callout>}}_E=\underset{i=M}{\overset{N}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;}+\mathrm{\&Delta;})\sin (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

${\mathrm{<figure-callout\; id="2"\; label="Q\; P"\; filenames="S2008101046011E00031.png"\; state="\{\{state\}\}">Q</figure-callout>}}_P=\underset{i=M}{\overset{N}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;})\sin (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

${\mathrm{<figure-callout\; id="2"\; label="Q\; L"\; filenames="S2008101046011E00031.png"\; state="\{\{state\}\}">Q</figure-callout>}}_L=\underset{i=M}{\overset{N}{\mathrm{\&Sigma;}}}s\left(t_i\right)C(t_i-\mathrm{\&tau;}-\mathrm{\&Delta;})\sin (2\mathrm{\&pi;}{f}_{d}t+\mathrm{\&theta;})$

Wherein, N is that the data sampling of 1ms is counted, and M is that the data sampling of the last period in two sections integrations is counted s (t _i) be sampling instant t _iThe signal that receives, C (t _i-τ+Δ), C (t _i-τ) and C (t _i-τ-Δ) represent sign indicating number morning of C/A sign indicating number respectively, instantaneous code and evening sign indicating number, the time delays of τ for estimating, Δ be sign indicating number early, instantaneous code, the code interval between evening yard, f _d, θ is respectively estimating Doppler frequency and original carrier phase place.

(6) symbol to the integration numerical value of the I branch road of the I branch road of first section instantaneous code and second section instantaneous code compares, and judges whether to exist navigation message data saltus step position; If two numerical symbols are identical, then there is not the data saltus step position of navigation message in explanation; If then there is the data saltus step position of navigation message in two numerical symbol differences.

(7) if there is the data saltus step position of navigation message, then the integration numerical value correspondence of two fragments that step (5) is obtained is subtracted each other, the if there is no data saltus step position of navigation message, the corresponding addition of two sections integration numerical value that then step (5) obtained obtains totally 6 integration numerical value.

If the i.e. I that obtains in the step (5) _P1And I _P2Then may there be the data saltus step position of navigation message in opposite in sign, at this moment:

I _E＝I _E1-I _E2； Q _E＝Q _E1-Q _E2

I _P＝I _P1-I _P2； Q _P＝Q _P1-Q _P2

I _L＝I _L1-I _L2； Q _L＝Q _L1-Q _L2

Otherwise, if I _P1And I _P2Symbol is identical, does not then have the data saltus step position of navigation message, at this moment:

I _E＝I _E1+I _E2； Q _E＝Q _E1+Q _E2

I _P＝I _P1+I _P2； Q _P＝Q _P1+Q _P2

I _L＝I _L1+I _L2； Q _L＝Q _L1+Q _L2

Like this, obtain I _E, I _P, I _L, Q _E, Q _P, Q _L6 integration numerical value.

(8) adopt described 6 integration numerical value to carry out loop filtering, calculate new carrier frequency, carrier phase and code phase, set the data saltus step position of floating type simultaneously, represent that with integral part the periodicity of data bit, fraction part represent the code phase that drifts about; Adopt new carrier frequency, carrier phase and code phase correction because the code phase drift that Doppler shift causes.

In the computation process of using isometric C/A sign indicating number, the frequency of navigation message also is subjected to the influence of Doppler frequency skew, and this trip point that causes navigation message can't occur in the position of integer number of milliseconds.If Doppler frequency be on the occasion of the time, trip point can progressively move to left; And Doppler frequency is when being negative value, and trip point can progressively move to right.Therefore, the present invention uses the floating type data to represent the position of navigation message data bit trip point, and wherein integral part is the trip point physical location, and fraction part is then represented the trip point position that is subjected to the code phase variable effect later.When Figure 7 shows that trip point with centesimal speed, the trip point situation under the floating-point method of counting.

(9) judge whether floating type data saltus step position crosses over integer, if the code phase drift of crossing over integer then existing Doppler shift to cause, by heavy synchronous amending method, revise because the navigation message drift that Doppler shift causes has been revised the back and waited for next data block; If do not cross over integer, next data block is waited in the code phase drift that does not then exist Doppler shift to cause.

(1) the CA sign indicating number cycle according to GPS is 1ms, and the navigation message frequency is 50Hz.Continuous 1 or continuously-1 number is 20 in the navigation message.

(2) be subjected to the influence of Doppler to the navigation message data transfer rate, when the floating-point part of the navigation message data of floating-point counting when forward passes through 0 (for example, becoming 0.99 from 1.01), continuous 1 or continuously-1 number is 21 in the navigation message.For guaranteeing in the navigation message that continuous 1 or continuously-1 number is 20, when floating type data saltus step position forward is crossed over integer, the saltus step bit position is moved one forward.

(3) be subjected to the influence of Doppler to the navigation message data transfer rate, when the floating-point part of the navigation message data of floating-point counting when oppositely passing through 0 (for example, becoming 1.01 from 0.99), continuous 1 or continuously-1 number may be 19 in the navigation message.For guaranteeing in the navigation message that continuous 1 or continuously-1 number is 20, when oppositely crossing over integer, the saltus step bit position is moved one backward in floating type data saltus step position.

Claims (3)

1. the software GPS receiver tracking method of an equal length CA code is characterized in that step is as follows:

(1) obtains the carrier frequency and the code phase information of last registration;

(2), read the carrier data of corresponding carrier frequency and carrier phase in the carrier wave look-up table according to the carrier frequency obtained;

(3) according to the code phase information of obtaining, dynamically produce isometric C/A sign indicating number look-up table, with the complexity that reduces to search;

(4), read isometric C/A sign indicating number corresponding in the described isometric C/A sign indicating number look-up table according to code phase information;

(5) adopt two sections integration methods, to gps signal, I and two carrier data of Q branch road that receive, and the isometric C/A sign indicating number that is read carries out I, Q branch road early sign indicating number, instantaneous code and late sign indicating number integration, obtain 12 integration numerical value behind two sections integrations altogether, avoided integration to cross over navigation message data saltus step position like this;

(6) symbol to the integration numerical value of the I branch road of the I branch road of first section instantaneous code and second section instantaneous code compares, and judges whether to exist navigation message data saltus step position;

(7) if there is the data saltus step position of navigation message, then two sections integration numerical value that step (5) is obtained subtract each other, the if there is no data saltus step position of navigation message, and then two sections integration numerical value addition that step (5) is obtained obtains totally 6 integration numerical value;

(8) adopt described 6 integration numerical value to carry out loop filtering, calculate new carrier frequency, carrier phase and code phase, set the data saltus step position of floating type simultaneously, represent that with integral part the periodicity of data bit, fraction part represent the code phase that drifts about; Adopt new carrier frequency, carrier phase and code phase correction because the code phase drift that Doppler shift causes;

(9) judge whether floating type data saltus step position crosses over integer, if the code phase drift of crossing over integer then existing Doppler shift to cause, by heavy synchronous amending method, revise because the navigation message drift that Doppler shift causes has been revised the back and waited for next data block; If do not cross over integer, next data block is waited in the code phase drift that does not then exist Doppler shift to cause;

The synchronous amending method of weight in the described step (9) is:

(a) the CA sign indicating number cycle according to GPS is Mms, and the navigation message frequency is DHz, and continuous 1 or continuously-1 number is n=1000/M/D in the navigation message;

(b) when the floating-point part of the navigation message data of floating-point counting when forward passes through 0, continuous 1 or continuously-1 number is n+1 in the navigation message, for guaranteeing in the navigation message that continuous 1 or continuously-1 number is n, when floating type data saltus step position forward is crossed over integer, the saltus step bit position is moved one forward;

(c) when the floating-point part of the navigation message data of floating-point counting when oppositely passing through 0, continuous 1 or continuously-1 number may be n-1 in the navigation message, for guaranteeing in the navigation message that continuous 1 or continuously-1 number is n, when integer is oppositely crossed in floating type data saltus step position, the saltus step bit position is moved one backward.

2. the software GPS receiver tracking method of equal length CA code according to claim 1 is characterized in that: two sections integrations are decomposed into former and later two sampling section with sampled signal at the code phase place for according to code phase information in the described step (5).

3. the software GPS receiver tracking method of equal length CA code according to claim 1, it is characterized in that: the method for judging the data saltus step position that has navigation message in the described step (6) is: if two numerical symbols are identical, then there is not the data saltus step position of navigation message in explanation; If then there is the data saltus step position of navigation message in two numerical symbol differences.

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