CN100523859C - Quick satellite selection method for combined satellite navigation system - Google Patents

Abstract

This invention provides a quick satellites choosing method for together fitted satellites system. It chooses satellites indirectly in this way: first, confirm the number of satellites in need. Then calculate the quadrant elevation and azimuth angle of visible satellites, set them to different parts and choose a group of satellites which has a medium quadrant elevation. Disposal the azimuth angle of the choosing satellites, combine the quadrant elevation information to remove some improper satellites. This satellite choosing method is quick, convenience and needs less calculation than the traditional one. Even it is not as precise as before, but it makes the navigational computer working more easily and guarantee the precision of together fitted navigation.

Description

A kind of quick satellite selection method of combined satellite navigation system

Technical field

The invention belongs to the satellite navigation field, be specifically related to a kind of satellite selection method of combined satellite navigation system.

Background technology

Enforcement along with Central European Galileo plan, satellite navigation will change to GNSS (GPS (Global Position System)) epoch from the GPS epoch, because GNSS possesses precision height, advantage such as covering the whole world, round-the-clock, form GPS, GALILEO and the multisystem of other system (as GLONASS, BD etc.) and the situation of depositing, the integrated navigation of multi-satellite navigation system will become an inexorable trend.During the navigation of multi-satellite navigation system in combination, as seen the star number order increases considerably, the reliability of bearing accuracy and system all is greatly improved, but the operand of navigator fix also is doubled and redoubled thereupon, the processor speed to receiver user requires to improve on the engineering in addition, therefore increased the weight of the burden of receiver user, its cost is risen.

In order to address the above problem, select star just to seem particularly important.Traditional satellite selection method has best geometric dilution of precision method and maximum volume method.

Best geometric dilution of precision method claims the best to select the star method again, in N the may observe satellite of all elevations angle greater than shield angle, choose m (m＜N) best satellite that distributes, promptly the traversal method is calculated the corresponding GDOP value of various possible combinations institute, and selects a group of GDOP value minimum as the optimal selection result.

$\mathrm{GDOP}=\sqrt{\mathrm{trace}{\left(H^{T}H\right)}^{-1}}---\left(1\right)$

Owing to need carry out

The calculating of inferior GDOP value, and the calculating of each GDOP value all relates to multiplication of matrices and invert, although therefore the best to select star method bearing accuracy be best, calculated amount is too big, the time that takies is oversize.

The maximum volume method is called accurate the best again and selects the star method.This method is developed by minimum GDOP method and obtains, but does not need the inversion operation of matrix, thereby has reduced the navigation calculating amount, but it is a kind of shortcut calculation that selects star when being applicable to less nautical star, is example with 4 satellites generally:

$\mathrm{GDOP}=\sqrt{\mathrm{trace}{\left(H^{T}H\right)}^{-1}}=\sqrt{\mathrm{trace}\frac{{\left(H^{T}H\right)}^{*}}{{\left|H\right|}^2}}=\frac{\sqrt{\mathrm{trace}{\left(H^{T}H\right)}^{*}}}{\left|H\right|}---\left(2\right)$

Wherein, $\left|H\right|=\left|\begin{array}{cccc}{e}_{11}& e_{12}& e_{13}& 1\\ e_{21}& e_{22}& e_{23}& 1\\ e_{31}& e_{32}& e_{33}& 1\\ e_{41}& e_{42}& e_{43}& 1\end{array}\right|=(\stackrel{\&RightArrow;}{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="C200710177375E00101.png"\; state="\{\{state\}\}">s</figure-callout>}}_2}u-\stackrel{\&RightArrow;}{s_{1}u})\&CenterDot;[(\stackrel{\&RightArrow;}{s_3}u-\stackrel{\&RightArrow;}{s_2}u)\&times;(\stackrel{\&RightArrow;}{s_4}u-\stackrel{\&RightArrow;}{s_3}u)]=6V$

Wherein,

Be respectively the unit vector of 4 satellites to the user, V is the tetrahedron ss that end points surrounded of 4 satellites to user's unit vector ₁s ₂s ₃s ₄Volume, so:

$\mathrm{GDOP}=\frac{\sqrt{\mathrm{trace}{\left(H^{T}H\right)}^{-1}}}{6V}=\frac{A}{6V}---\left(3\right)$

Order $A=\sqrt{\mathrm{trace}{\left(H^{T}H\right)}^{-1}}$

By formula (3) as can be known, GDOP value and tetrahedron s ₁s ₂s ₃s ₄Volume V be inversely proportional to, simultaneously V and A are the functions that satellite arrives user's unit vector, when when changing visible star and change V, the variation of A is very small, can think $\mathrm{GDOP}\&Proportional;\frac{1}{V}.$ Therefore normally replace directly calculating GDOP with the method for calculating tetrahedron volume V, with this as the foundation of selecting star.

When with GPS, GALILEO, GLONASS, when the BD2 four systems carries out integrated navigation, shield angle is made as 5 °, as seen star number is increased to more than 30, owing to need carry out space-time uniformity during the combined system navigation, state variable is increased to 7 dimensions from 4 dimensions thereupon, needs to select 7 optimum stars at least and positions.Best geometric dilution of precision method need be carried out Inferior GDOP computing, calculated amount is too big.The maximum volume method is because the number of the satellite that relates to is more, volume be difficult to calculate and calculated amount also very big, select star speed very slow, visible combined system selects star utilization tradition to select the star method to be difficult to realize.

Summary of the invention

The objective of the invention is to propose a kind of simple quick satellite selection method, from a plurality of satellite navigation systems, select the more excellent visible star of distribution, reduce the operand of positioning calculation effectively, realize quick satellite selection to sacrifice less bearing accuracy.

The quick satellite selection method of the combined satellite navigation system that the present invention proposes is on the basis according to traditional satellite selection method, it is poor that the elevation angle of visible star in the selected satellite navigation system and position angle are carried out layering, sort and done, remove the visible star of a part according to the regularity of distribution of getting rid of star, obtain the required position location satellite of choosing indirectly, selecting star between realization.Specifically realize by following steps:

1, determines the number of the required position location satellite of choosing according to the combined satellite navigation system positioning accuracy request.

2, the elevation angle and the position angle of visible star in the calculation combination satellite navigation system, and the visible star elevation angle is divided into the low elevation angle, the middle elevation angle, three zones, the high elevation angle, the visible star in the elevation angle in selecting is determined the visible star number purpose ratio at the high elevation angle and the low elevation angle.

3, the position angle of the visible star in the middle elevation angle selected in the step 2 is sorted, done poor, in conjunction with the number ratio of visible star in the high elevation angle and the low elevation angle, the visible star of the part in the eliminating in the zone, the elevation angle realizes choosing indirectly position location satellite again.

Method provided by the invention has the following advantages:

1, selecting star method realized selecting star between this method adopted, and had solved the big problem of traditional satellite selection method calculated amount effectively, can realize simple, quick satellite selection.

2, this method reduces the navigation operations amount effectively to sacrifice less bearing accuracy, reduces the burden of navigational computer, has also guaranteed the integrated navigation advantage of high precision.

3, this method is fit to multiple combined satellite navigation system navigator fix in the world.

Description of drawings

Fig. 1 is the process flow diagram of the quick satellite selection method of combined satellite navigation system;

Visible satellite position angle, the elevation view of Beijing area when Fig. 2 is t=12h.

Embodiment

The present invention is described in further detail below in conjunction with the drawings and specific embodiments.

The invention provides a kind of quick satellite selection method of combined satellite navigation system, described method flow is specifically realized by following steps as shown in Figure 1:

Step 1: the number m that determines required position location satellite according to the combined satellite navigation system positioning accuracy request.At first all satellites in the selected system are numbered, draw the numbering of visible star in system's satellite, and each visible star is all distinguished according to numbering separately.If total visible star number is K in the combined system at this moment.Under the condition that range error is determined, the GDOP value has reflected the size of bearing accuracy, and promptly the more little bearing accuracy of GDOP value is high more.Adopt the traversal method can obtain selecting the changes delta GDOP of star front and back GDOP value and relation such as the table 1 of selected location number of satellite m:

The relation of table 1 Δ GDOP and selected location number of satellite m

With respect to the single system location, the outstanding advantage of combined system location is the bearing accuracy height, and the GDOP value is less.For the advantage that guarantees that the combined system bearing accuracy is high, the number of selected position location satellite can not be very few, quick satellite selection method provided by the invention is applicable to that selected location number of satellite is no less than the situation of 60% visible star, in this scope, table 1 has provided the relation of Δ GDOP and selected location number of satellite m.The data that provide according to table 1, m/K is an empirical value, and the user can rationally finely tune the m/K value according to GDOP value after selecting star, the Δ GDOP in the certain allowed band of the back acquisition of fine setting experiment for several times, be met the best m/K value of positioning accuracy request, promptly obtain required position location satellite number.

Step 2: the elevation angle and the position angle of visible star in the calculation combination satellite navigation system, and the visible star elevation angle is divided into the low elevation angle, the middle elevation angle, three zones, the high elevation angle, the visible star in the elevation angle in selecting is determined the visible star number purpose ratio at the high elevation angle and the low elevation angle.

The system position of visible star under user's horizontal coordinates of setting up departments is (x _L, y _L, z _L), then

As seen the star elevation angle: $\mathrm{EL}={\tan }^{-1}\left(\frac{z_L}{\sqrt{{x_{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C200710177375E00101.png"\; state="\{\{state\}\}">L</figure-callout>}}}^2+{y_L}^2}}\right)---\left(4\right)$

As seen star position angle: $A={\tan }^{-1}\left(\frac{x_L}{y_L}\right)---\left(5\right)$

The observing matrix of combined system:

$H_{\mathrm{comb}}=\left[\begin{array}{ccccc}{H}_1^{\&prime;}& 1& \&CenterDot;\&CenterDot;\&CenterDot;& \&CenterDot;\&CenterDot;\&CenterDot;& 0\\ {\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="C200710177375E00101.png"\; state="\{\{state\}\}">H</figure-callout>}}_2^{\&prime;}& 0& 1& \&CenterDot;\&CenterDot;\&CenterDot;& 0\\ \&CenterDot;\&CenterDot;\&CenterDot;& \&CenterDot;\&CenterDot;\&CenterDot;& \&CenterDot;\&CenterDot;\&CenterDot;& \&CenterDot;\&CenterDot;\&CenterDot;& \&CenterDot;\&CenterDot;\&CenterDot;\\ H_S^{\&prime;}& 0& 0& \&CenterDot;\&CenterDot;\&CenterDot;& 1\end{array}\right]---\left(6\right)$

Wherein Preceding 3 row for the Navsat observing matrix of user and S system.

$H_{\mathrm{Si}}^{\&prime;}=\left(\begin{array}{ccc}{e}_{\mathrm{ix}}& e_{\mathrm{iy}}& e_{\mathrm{iz}}\end{array}\right)=\left(\begin{array}{ccc}\cos {\mathrm{EL}}_i\sin A_i& \cos {\mathrm{EL}}_i\cos A_i& \sin E_i\end{array}\right)---\left(7\right)$

S is system's number of combined system, S=1,2 I (i=1,2 ... k) be the visible star number order of each system.

Bring the position coordinates of the visible star of system into the elevation angle and position angle that formula (4) and formula (5) can obtain the visible star of system, formula (6) and the matrix shown in the formula (7) are only relevant with the elevation angle and the position angle of system visible star, and bring formula (6) and formula (7) into formula (1), can calculate the geometric dilution of precision GDOP of combined system, visible GDOP is only relevant with the elevation angle and the position angle of visible star.Satellite selection method provided by the invention by to the elevation angle and azimuthal judgement of visible star, select star, need not carry out a large amount of traversals of GDOP value of traditional satellite selection method and calculate, the utmost point has shortened the star time of selecting effectively.

Because the position location satellite number more (being that the m value is bigger) that obtains in the step 1, and the number of satellite value that is excluded less (being that the K-m value is less), so use among the present invention and determine that the regularity of distribution that is excluded satellite realizes choosing indirectly position location satellite.According to minimum GDOP method traversal emulation experiment statistics, the eliminating star of selecting all is in the satellite that the elevation angle is 30 °≤EL≤60 °, so among the present invention layering is carried out at the elevation angle of the visible satellite of K in the system, be divided into three zones: 0 °≤EL＜30 °, 30 °≤EL≤60 °, 60 °＜EL≤90 °, be called the low elevation angle, the middle elevation angle and the high elevation angle, select the visible star (promptly in elevation angle satellite) of the elevation angle between 30 °≤EL≤60 °, and calculate respectively the elevation angle and count k greater than 60 ° (high elevations angle) with less than the satellite at 30 ° (low elevations angle) ₁, k ₂

The volume V that the more little then satellite of satellite GDOP is formed to user's vector is big more, and the satellite at the elevation angle is smaller to the influence of volume V with respect to the high elevation angle and low elevation angle satellite in being in, and this is corresponding to the maximum volume method.If the difference at the position angle in the satellite of the middle elevation angle between two satellites is very little, remove wherein one, can be littler for the distribution influence of whole volume V, thus the eliminating star of selecting among the present invention all come from elevation angle satellite.

Step 3: it is poor that the position angle of the visible star in the middle elevation angle selected in the step 2 is sorted, done, and in conjunction with visible star number purpose ratio in the high elevation angle and the low elevation angle, the visible star of the part in the eliminating in the zone, the elevation angle realizes choosing indirectly position location satellite again.

According to the maximum volume ratio juris, because $\mathrm{GDOP}\&Proportional;\frac{1}{V},$ For locating accuracy is improved, the volume V that selected position location satellite is formed to user's unit vector should be as far as possible near maximum, to guarantee to obtain minimum GDOP value.For the visible star that is in ° elevation coverage of 30 °≤EL≤60, if wherein any two satellite aximuths are more approaching,, get rid of wherein one then in conjunction with elevation angle distributed intelligence, this eliminating to volume distributed median V to influence meeting very little.According to the priori experiment statistics, the nationwide, when shield angle was 5 °, the elevation angle was being compared k greater than 60 ° of (the high elevation angle) satellites and the elevation angle in the average number less than 30 ° of (the low elevation angle) satellites ₁: k ₂≈ 1:3, if certain is constantly k ₁: k ₂＜1:3 just selects higher elevation angle satellite, gets rid of the elevation angle on the low side satellite, replenishes short transverse information; Otherwise, just select the elevation angle on the low side satellite, get rid of high elevation angle satellite, replenish horizontal direction information.

To the middle elevation angle satellite that obtains in the step 2, sort in the position angle of the visible star that is the elevation angle between 30 °≤EL≤60 °, every adjacent two visible stars are one group, calculate position angle poor of every group of two satellites, again azimuthal difference is sorted from small to large, select the preceding K-m group satellite of position angle difference minimum, again according to k ₁, k ₂Proportionate relationship, get rid of in every group of two satellites.Finally draw the numbering of getting rid of star, just can draw the numbering of choosing satellite indirectly, realize choosing of position location satellite.Special circumstances are, if according to k ₁, k ₂Proportionate relationship, the visible astrology in the low elevation angle (the high elevation angle) in the visible star in the low elevation angle of getting rid of in a certain group (the high elevation angle) and another group together, then another group is got rid of the visible star in the high elevation angle, be equivalent to have the position angle of three visible stars more approaching this moment, in these three visible stars, get rid of two, only keep a visible star.

Further specify the present invention with concrete numerical value below.GPS, GALILEO, GLONASS, BD2 four systems are carried out integrated navigation, and the user selects the Beijing area for use, and shield angle is made as 5 °, and bearing accuracy reduces by 10% after supposing to require to select star.Utilize method provided by the invention that four system in combination satellite navigation systems are selected star, concrete steps are:

Step 1: the number m that determines required position location satellite according to the combined satellite navigation system positioning accuracy request.

Satellite to each system is numbered: GPS (1-24), GLONASS (25-48), GALILEO (49-75), BD2 (76-87).Be reduced to 10% requirement according to bearing accuracy after selecting star, Δ GDOP=10%, get the ratio m/K=3/4 that selects star number order m and all visible star number order K at this moment by table 1, select that the GDOP value of satellite has increased by 10.2% behind the star, therefore finely tune m/K=0.76 and make the GDOP value of selecting behind the star increase by 10%, can get rid of the relatively poor visible star of 24% distribution.T=12h when getting GPS, the number of visible star is 35 in the system at this moment, the position distribution of visible star and numbering are as shown in Figure 2.Orientation/the elevation view of 35 visible satellites in Fig. 2 represents Beijing user obtains when being t=12h the four systems, the visible star that the visible star representative that square marks is excluded.The user is in the concentrically ringed center of circle, circle centre position is represented 90 ° of elevations angle, outermost circle is represented 0 ° of elevation angle (or local horizon), each circle ecto-entad is followed successively by and increases by 10 °, second justifies on the elevation angle that is in 10 °, and the rest may be inferred, up to 90 ° of elevation location of circle centre position, among Fig. 2 the orientation to positive north orientation be 0 °, and increase in the direction of the clock.For the accuracy requirement that guarantees above-mentioned Δ GDOP=10% can be got rid of 8 visible stars, remaining 27 visible stars are as position location satellite.

Step 2: the elevation angle and the position angle of visible star in the calculation combination satellite navigation system, and the visible star elevation angle is divided into the low elevation angle, the middle elevation angle, three zones, the high elevation angle, the visible star in the elevation angle in selecting is determined the visible star number purpose ratio at the high elevation angle and the low elevation angle.The elevation angle and the position angle of calculating visible star are respectively:

EL ₁＝46.292，EL ₂＝80.911，EL ₃＝7.8145，……，EL ₃₄＝50.828，EL ₃₅＝54.228；

A ₁=212.94, A ₂=163.33, A ₃=36.511 ..., A ₃₄=293.84, A ₃₅=191.88; The visible star of selecting between ° elevation angle, 30 °≤EL≤60 has 19, and numbering is respectively:

1，13，14，23，26，……81，86，87

K is counted greater than 60 ° satellite in the elevation angle ₁=2, k is counted less than 30 ° satellite in the elevation angle ₂=14, k then ₁: k ₂＜1:3.

Step 3: it is poor that the position angle of the visible star in the middle elevation angle selected in the step 2 is sorted, done, and again in conjunction with the high elevation angle and low elevation information, the visible star of the part in the eliminating in the zone, the elevation angle realizes choosing indirectly position location satellite.Concrete steps are:

(a) position angle of 19 visible stars in the middle elevation angle selecting in the step 2 sorted from small to large:

22.932，48.83，50.746，……295.78，299.48

(b) with about every two adjacent visible stars be divided into one group, have 18 groups, and poor to the position angle of two visible stars in every group, difference is respectively:

25.898，1.916，4.508，……，0.306，3.70

(c) the azimuthal difference of gained sorts from small to large in the step (b), and selects the position angle difference of preceding 8 groups satellite to be:

0.306，1.628，1.916，2.631，3.590，3.703，4.508，8.950

(d) from step 2 k as can be known ₁: k ₂＜1:3 so get rid of a less visible star of the elevation angle in preceding 8 groups every group two visible stars, obtains 8 numberings of getting rid of star and is respectively:

31，60，78，77，26，87，81，13

The numbering of being numbered 27 visible satellites that just can obtain indirectly choosing by all visible star numberings and eliminating star in the four systems is respectively:

1，2，5，14，17，……79，80，86

Realize choosing of position location satellite.

In like manner, the ordering of above-mentioned position angle and position angle difference is carried out according to order from big to small, corresponding preceding 8 groups is 8 groups of backs, also can obtain getting rid of the numbering of star and visible star equally.

Empirical tests: after using quick satellite selection method provided by the invention and choosing position location satellite, reduce 10% based on user's bearing accuracy, if the user selects for use least square method to position, system's navigation operations amount reduces 23.5% before selecting star after selecting star; If the user selects for use weighted least-squares method to position, system's navigation operations amount can reduce 38.2% before selecting star after selecting star.Quick satellite selection method provided by the invention can reduce the navigation operations amount effectively under the situation that guarantees the combined system bearing accuracy, reduce the burden of navigation neceiver processor.

The quick satellite selection method of combined satellite navigation system of the present invention ascertains the number more by getting rid of a small amount of satellite indirectly Position location satellite, this method have overcome the big shortcoming of traditional satellite selection method amount of calculation, can realize simple, quick satellite selection. At this Adopt the less positioning accuracy (such as 10%) of sacrifice effectively to reduce the navigation operations amount in the invention, reduce the negative of navigational computer Load has also guaranteed the high advantage of integrated navigation precision. Method provided by the present invention is fit to the multiple combination satellite navigation system entirely Navigator fix in the ball scope.

Claims (4)

1, a kind of quick satellite selection method of combined satellite navigation system is characterized in that comprising the steps:

Steps A, determine the required number of choosing position location satellite according to the combined satellite navigation system positioning accuracy request;

The elevation angle and the position angle of visible star in step B, the calculation combination satellite navigation system, and the visible star elevation angle is divided into the low elevation angle, the middle elevation angle, three zones, the high elevation angle, the visible star in the elevation angle in selecting is determined the ratio of the number of satellite at the high elevation angle and the low elevation angle;

Step C, the position angle of the visible star in the middle elevation angle selected among the step B is sorted, done poor, again in conjunction with the high elevation angle and low elevation information, the visible star of the part in the eliminating in the zone, the elevation angle realizes choosing indirectly position location satellite.

2, the quick satellite selection method of combined satellite navigation system according to claim 1 is characterized in that: the number of choosing position location satellite in the steps A can not be less than 60% of total visible star in the system.

3. the quick satellite selection method of combined satellite navigation system according to claim 1 is characterized in that among the step B visible star elevation angle EL being divided into three zones, is respectively 0 °≤EL＜30 °, 30 °≤EL≤60 °, 60 °＜EL≤90 ° three zones.

4. according to the quick satellite selection method of the described combined satellite navigation system of claim 1, it is characterized in that step C can carry out as follows:

(a) the visible star in the middle elevation angle that obtains among the step B is sorted;

(b) position angle of every adjacent two the visible stars in calculating ordering back is poor, the more azimuthal difference that obtains is sorted;

(c) select the immediate preceding K-m group satellite in position angle, wherein K is a visible star number total in the combined system, and m is the number of required position location satellite;

(d) according to the k that obtains among the step B ₁, k ₂Proportionate relationship get rid of in every group of two satellites wherein one, obtain K-m the numbering of getting rid of star respectively, realize choosing indirectly position location satellite, k wherein ₁, k ₂Be respectively the elevation angle greater than 60 ° with less than 30 ° satellite number.

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