CN103116172A - False detection method of satellite navigation signal and satellite navigation positioning receiver - Google Patents
False detection method of satellite navigation signal and satellite navigation positioning receiver Download PDFInfo
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Abstract
The invention discloses a false detection method of a satellite navigation signal. Based on an initial position of a receiver, the method calculates a general location parameter, relative to the receiver, of a satellite, wherein the general location parameter is corresponding to the received satellite navigation signal, if the general location parameter is not within an observation vision field of the receiver, the general location parameter is judged to be a false signal, and the method further carries out false detection through calculating error distance of a spatial position of the satellite. The invention further discloses a satellite navigation positioning receiver. Through the above way, the method detects the false navigation signal through analyzing navigation message contents, strengthens anti-spoofing ability of the receiver, and further has the advantages of being low in implementation cost, strong in expansibility, capable of being firmly combined with the application mode of the receiver and the like.
Description
Technical field
The present invention relates to the satellite navigation field, particularly relate to false detection method and the satellite navigation location receiver of satellite navigation signals.
Background technology
Along with the generally application in China of GPS and " Big Dipper " satellite navigation location and time service business, the industry department that national economy is had material impact, as communication, electric power, traffic etc., not only the accuracy of satellite navigation location and time service business had higher requirements, its dependence is also strengthened greatly, mainly or fully via satellite navigator fix and time service provides infrastructure service and technical support, therefore the security of satellite navigation location and time service business proposed requirements at the higher level.
The real satellite that disguises oneself as navigation signal carries out duplicity to satellite navigation receiver to be disturbed and to have become a kind of important threat that satellite navigation location and Timing Receiver face.If satellite navigation location and Timing Receiver are not taked the measures such as effective identification, detection for this false curve through camouflage, so in a single day, this false curve is received and this signal is resolved and obtains false navigator fix and time service information, making receiver produce wrong position and time, will be huge to the negative effect of important sector of the national economy so.Time service type satellite navigation receiver particularly, utilize such receiver can obtain temporal information accurately, satisfy the application that time precision, time synchronized etc. is had higher requirements, if but this temporal information is distorted arbitrarily, replaces and confuse by false curve, bring confusion can for so national economy, social life, even affect social stability.
In the prior art, mainly laying particular emphasis on detection research at signals layer for the detection method of false satellite navigation signals, is namely that the situations such as centre carrier frequency, waveform, frequency spectrum, power to the satellite navigation signals that receives are carried out static state or performance analysis.These methods are used for the detection of false satellite navigation signals reference frame are provided, but in some concrete applications, these methods are difficult to and the combining closely of practical application condition, and therefore do not have advantage aspect dirigibility, practicality, accuracy, validity and the technical costs used.
Summary of the invention
The technical matters that the present invention mainly solves is to provide a kind of false detection method and satellite navigation location receiver of satellite navigation signals, can carry out the falseness detection to satellite navigation signals based on initial position and the almanac of receiver.
For solving the problems of the technologies described above, the technical scheme that the present invention adopts is: a kind of false detection method of satellite navigation signals is provided, and the method comprises, when receiver is started shooting, carry out initial alignment by this receiver, obtain the initial position of this receiver according to positioning result; Receive and the tracking satellite navigation signal, calculate the general location parameter of the satellite corresponding with this satellite navigation signals according to the reference almanac of this initial position and the storage of this receiver; Judge that according to this general location parameter this satellite is whether in the observation visual field of this receiver; When the determination result is NO, determine that this satellite navigation signals is spurious signal.
In another embodiment of the false detection method of satellite navigation signals of the present invention, this detection method also comprises: judgment result is that when being, calculate the reference locus of this satellite with reference to almanac according to this, calculate the current locus of this satellite according to the current almanac in this satellite navigation signals, and calculate the reference locus of this satellite and deserve error distance between the front space position; Judge that whether this error distance is greater than threshold value; During greater than this threshold value, determine that this satellite navigation signals is spurious signal at this error distance.
In another embodiment of the false detection method of satellite navigation signals of the present invention, this detection method also comprises: when this error distance is less than or equal to this threshold value, determine that this satellite navigation signals is actual signal, replaces this with reference to almanac with this current almanac.
In another embodiment of the false detection method of satellite navigation signals of the present invention, this general location parameter comprises position angle and the elevation angle.
In another embodiment of the false detection method of satellite navigation signals of the present invention, this initial position is that the positioning result to the continuous several times initial alignment carries out the position that mean value computation obtains.
In another embodiment of the false detection method of satellite navigation signals of the present invention, this initial alignment is at least 10 times, the threshold condition of this mean value computation comprises: three-dimensional accuracy geometric factor＜3, satellite number 〉=5, the residual error of the least square iteration of positioning calculation＜0.01, the repeatedly longitude and latitude between the positioning result of initial alignment, elevation poor＜30 meter.
In another embodiment of the false detection method of satellite navigation signals of the present invention, after this initial position is determined, the location parameter of outside this receiver determined of this receiver is input to this receiver, and this initial position is proofreaied and correct.
In another embodiment of the false detection method of satellite navigation signals of the present invention, when the acquisition time of this current almanac and this interval with reference to the update time of almanac were less than or equal to 1 day, this threshold value was 1 kilometer; When large 1 day of the acquisition time of this current almanac and this interval with reference to the update time of almanac, and when being less than or equal to 5 days, this threshold value was 5 kilometers; With reference to the interval of the update time of almanac during greater than 5 days, this threshold value is 10 kilometers when the acquisition time of this current almanac and this.
The present invention also provides a kind of satellite navigation location receiver, and this receiver comprises: positioning unit, and be used for this receiver and carry out initial alignment, calculate the initial position of this receiver according to positioning result; Signal element is used for receiving and the tracking satellite navigation signal, calculates the general location parameter of the satellite corresponding with this satellite navigation signals according to the reference almanac of this initial position and the storage of this receiver; The first judging unit is used for judging that according to this general location parameter this satellite is whether in the observation visual field of this receiver; Performance element is used for when the determination result is NO, determining that this satellite-signal is spurious signal at this first judging unit.
In another embodiment of satellite navigation location receiver of the present invention, this receiver also comprises: computing unit, be used for when judgment result is that of this first judging unit is, calculate the reference locus of this satellite with reference to almanac according to this, calculate the current locus of this satellite according to the current almanac in this satellite navigation signals, and calculate this with reference to the locus and deserve error distance between the front space position; The second judging unit is used for judging that whether this error distance is greater than threshold value; This performance element is further used for during greater than this threshold value, determining that this satellite navigation signals is spurious signal at this error distance; And when this error distance is less than or equal to this threshold value, determine that this satellite navigation signals is actual signal, replaces this with reference to almanac with this current almanac.
In another embodiment of satellite navigation location receiver of the present invention, this general location parameter comprises position angle and the elevation angle.
In another embodiment of satellite navigation location receiver of the present invention, when the acquisition time of this current almanac and this interval with reference to the update time of almanac were less than or equal to 1 day, this threshold value was 1 kilometer; When large 1 day of the acquisition time of this current almanac and this interval with reference to the update time of almanac, and when being less than or equal to 5 days, this threshold value was 5 kilometers; With reference to the interval of the update time of almanac during greater than 5 days, this threshold value is 10 kilometers when the acquisition time of this current almanac and this.
The invention has the beneficial effects as follows: by in conjunction with the initial position of receiver with reference to almanac, the general location parameter of the satellite that the satellite navigation signals that calculating receives is corresponding, determine that according to the general location parameter satellite is whether in the receiver observation visual field, with this, navigation signal being carried out falseness detects, do not need additionally to increase hardware facility, have the advantages such as implementation method is flexible, extendability is strong, cost is low, can strengthen anti-deception ability.
Description of drawings
Fig. 1 is the schematic flow sheet of false detection method first embodiment of the satellite navigation signals according to the present invention;
Fig. 2 is the schematic flow sheet of false detection method second embodiment of the satellite navigation signals according to the present invention;
Fig. 3 is the structural representation of satellite navigation location receiver the first embodiment according to the present invention;
Fig. 4 is the structural representation of satellite navigation location receiver the second embodiment according to the present invention;
Fig. 5 is the schematic flow sheet of false detection method the 3rd embodiment of the satellite navigation signals according to the present invention;
Fig. 6 is the schematic flow sheet of false detection method the 4th embodiment of the satellite navigation signals according to the present invention;
Fig. 7 is the structural representation of satellite navigation location receiver the 3rd embodiment according to the present invention;
Fig. 8 is the structural representation of satellite navigation location receiver the 4th embodiment according to the present invention;
Fig. 9 is the schematic flow sheet of false detection method the 5th embodiment of the satellite navigation signals according to the present invention;
Figure 10 is the structural representation of satellite navigation location receiver the 5th embodiment according to the present invention;
Figure 11 is the schematic flow sheet of false detection method the 6th embodiment of the satellite navigation signals according to the present invention.
Embodiment
At first, need to explicitly point out be method that the embodiment of the present invention adopts be based on the satellite navigation signals that receives is carried out demodulation after, can obtain the information such as navigation message wherein, so the embodiment of the present invention is a kind of anti-deception measures on the information aspect.
The present invention is described in detail below in conjunction with drawings and Examples.
Fig. 1 has shown the schematic flow sheet of false detection method first embodiment of satellite navigation signals of the present invention.This falseness detection method comprises the following steps:
Step S101: when receiver is started shooting, carry out initial alignment by receiver, obtain the initial position of receiver according to positioning result.
Wherein, at first to determine the initial position of satellite navigation location receiver.Receiver in the embodiment of the present invention is fixedly mounted on a certain position usually, or the time service type receiver that does not move in the long period.Therefore, the residing position coordinates of this receiver, namely the initial position of this receiver both can utilize the machine to position acquisition, also can obtain according to known accurate location information, namely utilized accurate location coordinate that the receiver outside obtains to be input to receiver inside as a reference or proofreaied and correct foundation.When positioning, normally when starting shooting for the first time, receiver carries out, in order to guarantee the accuracy of initial alignment, generally need continuous several times to locate, for example be taken to few 10 continuous positioning results, positioning result to these at least 10 initial alignments carries out mean value computation, the threshold condition of mean value computation comprises: PDOP(Position Dilution of Precision, the three-dimensional accuracy geometric factor)＜3, satellite number 〉=5, each other longitude and latitude of the residual error of the least square iteration during positioning calculation＜0.01, multiple bearing result, elevation poor＜30 meters.With the position of this mean value computation initial position as this receiver.Certainly, after this initial position is determined, also the location parameter of outside this receiver determined of this receiver can be input to this receiver, so that this initial position is proofreaied and correct, improve the accuracy of initial position.
Step S102: receive and the tracking satellite navigation signal, calculate the general location parameter of the satellite corresponding with satellite navigation signals according to the reference almanac of initial position and receiver storage.
Wherein, comprise navigation message in satellite navigation signals, include the information such as satellite ephemeris, almanac, satellite clock, satellite health situation and precision in navigation message.When utilizing satellite to position, determine that in advance satellite is vital in the position in space, especially receiver instrumented satellite navigation signal is from that satellite spatial position constantly of satellite launch, this need to take out satellite orbit parameter from navigation message, be ephemeris, Calculation of Satellite physical location at that time.Each satellite is also broadcasted the simple ephemeris of all satellites in constellation in navigation message except the ephemeris of broadcasting oneself, the latter is called almanac.Almanac is used for estimating the apparent position of satellite, and the precision of its parameter does not have ephemeris parameter accurate like that.Therefore, say from purposes, almanac comprises the Position Approximate of whole satellites, is used for the satellite position forecast; Ephemeris is the exact position of the satellite that observes of present receiving machine, is used for the location.Utilize ephemeris or almanac Calculation of Satellite locus equation:
Wherein, (X
i, Y
i, Z
i) be the locus of satellite in the body-fixed coordinate system take the earth's core as initial point, r be satellite to the distance in the earth's core, Ω is right ascension of ascending node, i is inclination of satellite orbit, Ф is the argument of perigee.Here, parameter r, Ω, i and Ф can be obtained by ephemeris or almanac.
Utilize almanac and local position, can calculate satellite with respect to position angle and the elevation angle on observation ground, can calculate thus satellite and duration that the locality can observe, namely the satellite elevation angle is greater than the time of occurrence of 5 °.
Utilize the ultimate principle equation that satellite positions to be:
In formula, (X, Y, Z) is receiver location, (X
i, Y
i, Z
i) be satellite position, all in the body-fixed coordinate system take the earth's core as initial point, c is the light velocity in these two positions, Δ t is the clock correction of receiver and satellite, ρ
iBe receiver to the pseudorange of satellite, i=1,2,3,4 show and need at least 4 satellites to resolve.This shows, in order to determine the position at receiver place, need to know the locus of satellite, and satellite is to the pseudorange between receiver, then carry out certain error correction, just can obtain receiver location comparatively accurately.(X
i, Y
i, Z
i) be to obtain the position of satellite by ephemeris or almanac, and ρ
iTo obtain by pseudo-random code ranging.
Receiver receives after satellite navigation signals constantly tracking satellite navigation signal, and obtain navigation message from satellite navigation signals, the embodiment of the present invention is utilized the almanac in navigation message, by the locus of satellite being calculated and relatively carrying out falseness and detect.Wherein, must have accurately almanac as a reference, the last time can be obtained and be come from true navigation signal almanac as a reference, this almanac is stored, claims this almanac for reference to almanac here.Because the data volume of almanac is larger, the update cycle is longer, and provides the general location information of satellite, use almanac Calculation of Satellite position can only reach the precision of kilometer level, but this kilometer class precision can remain unchanged in a long time.Therefore, the reference almanac that receive to obtain in the initial alignment process is accurately under prerequisite, is also accurately in its accuracy rating by this satellite position that calculates with reference to almanac in a long time.
For the satellite navigation signals that receives, both comprised the satellite navigation signals that the satellite that newly enters the receiver visual field sends, also may receive false satellite navigation signals.False satellite navigation signals can be divided into by producing method: production and relay type.Production is the autonomous deception navigation signal that produces of deception device, and purpose is receiver to be resolved depart from actual position or time; Relay type is to forward the navigation signal that postpones through certain, also can make receiver produce errors present or temporal information.In step S102, navigation message in the satellite navigation signals that receives is resolved, therefrom can obtain the identity information of this satellite, it is the satellite identifier, then according to this satellite identifier, utilization can obtain the volume coordinate position of this satellite with reference to almanac, and for ease of explanation, the volume coordinate positional representation of this satellite that obtains by the reference almanac is (X
i, Y
i, Z
i), and and receiver in a coordinate system.Then by co-ordinates of satellite (X
i, Y
i, Z
i) and receiver coordinate (X, Y, Z) can calculate this satellite with respect to the general location parameter of this receiver, this general location parameter comprises that this satellite is with respect to parameters such as the position angle of ground receiver, the elevations angle, because the coordinate in same coordinate system of this satellite and receiver all obtains, therefore the general location parameter is easy to obtain, and can reflect the relative position relation of this satellite and ground receiver.
Take satellite with respect to the position angle of receiver and the elevation angle as example, its computation process is as follows: at first, in the topocentric coordinate system take receiver as initial point, calculate satellite with respect to the rectangular coordinate of receiver:
Wherein, (x in topocentric coordinate system
N, y
E, z
U) be satellite with respect to the position of receiver, L, B are respectively geodetic longitude and the geodetic latitudes of receiver, (X, Y, Z) is the position of receiver, (X
i, Y
i, Z
i) be the locus of satellite.
Then, by the relation between rectangular space coordinate and polar coordinates:
Wherein
El is the satellite elevation angle, and Az is satellite aximuth.Draw position angle and the elevation angle of satellite:
Step S103: judge that according to the general location parameter satellite is whether in the observation visual field of receiver; When the determination result is NO, determine that satellite navigation signals is spurious signal.
Wherein, because satellite moves on planned orbit around the earth, therefore each satellite passes through the time in overhead, a certain region, and position angle and the elevation angle with respect to receiver can and be calculated with reference to almanac according to the receiver initial position in this overhead, region.If what receive is real satellite navigation signals, this satellite azimuth angle and elevation angle that calculates can reflect that current satellite is in the observation visual field of region, receiver place; If what receive is false satellite navigation signals, the position angle and the elevation angle that calculate so this satellite of observation just might be within sweep of the eye not observable in the receiver current location.For example, when receiver normally receives the navigation signal that satellite sends, need satellite to be greater than 5 ° with respect to the elevation angle of receiver, and the elevation angle that calculates is 1 °, what this manifest error explanation received is spurious signal.After definite satellite navigation signals was spurious signal, receiver can send early warning, for example by the early warning pilot lamp glimmer alarm, stop location and/or time service information output.
By the present embodiment, only need to just can calculate satellite with respect to the general location of receiver according to almanac and receiver initial position, for can straightforward judgement being not spurious signal at the satellite of observing the visual field, have the simple advantage of implementation method.
Fig. 2 is the schematic flow sheet of false detection method second embodiment of satellite navigation signals of the present invention.Step S201 in Fig. 2, S202, S203 and step S207 have the technical characterictic identical with step S101, S102, S103 in Fig. 1, repeat no more herein.And in step S203, whether satellite is detected in the observation visual field of receiver, testing result is in the observation visual field of receiver region, is not enough to also illustrate whether satellite navigation signals is true, also needs further the satellite navigation signals that receives to be carried out falseness and detects.This is because Calculation of Satellite with respect to position angle and the elevation angle of receiver, is summary to satellite position to be calculated, and can't get on from the volume coordinate position of satellite to judge more accurately.If judgment result is that of step S203 is to carry out step S204.
Step S204: calculate the reference locus of satellite according to the reference almanac, calculate the current locus of satellite according to the current almanac in satellite navigation signals, and the reference locus of Calculation of Satellite and the error distance between current locus.
Wherein, at first need to complete two computation processes.First calculating is according to the satellite identity in the navigation message that receives, i.e. satellite identifier, and with reference to almanac, this satellite is carried out track calculate, can obtain the locus of this satellite, use coordinate (X herein
sr, Y
sr, Z
sr) co-ordinates of satellite that obtains by the reference almanac of expression, and be referred to as satellite with reference to the locus.By as can be known aforementioned, because the almanac update cycle is longer, after after a while, when utilizing almanac that previous time period obtains to the satellite spatial position calculation, the accuracy meeting descends, but within a period of time, in 10 days, its error precision but still has higher stability, normally in the error range of kilometer level; Second calculating is according to the satellite identity in the navigation message that receives and upgrades almanac, i.e. current almanac, and the locus of calculating this satellite is used coordinate (X herein
sc, Y
sc, Z
sc) co-ordinates of satellite that obtains by current almanac of expression, and be referred to as satellite current locus.Then, satellite is compared with reference to locus and this satellite current locus, calculate exactly the distance between these two locus, namely
Here be referred to as the error distance of these two locus.
Step S205: whether error in judgement distance greater than threshold value, if, execution in step S207, if not, execution in step S206.
Wherein, threshold value chooses T update time with the reference almanac
fAnd the acquisition time T of current almanac
cThe interval relation is arranged, for example, work as T
c-T
f≤ 1 day, threshold settings was 1 kilometer; As 1 day＜T
c-T
f≤ 5 days, threshold settings was 5 kilometers; Work as T
c-T
f5 days, threshold settings is 10 kilometers.
Step S206: determine that satellite navigation signals is actual signal, replace with reference to almanac with current almanac.
Wherein, if error distance is less than or equal to threshold value, show that the satellite navigation signals that receives has higher confidence level, can receive navigation message wherein, and replace with reference to almanac with current almanac, namely replace as new reference almanac with current almanac existing with reference to almanac, and acquisition time T that will this current almanac
cT update time as new reference almanac
f, this current almanac will be as the reference almanac of late detection (such as start next time).
If error distance is greater than this threshold value, explanation calculates by the navigation message that receives satellite spatial position is equipped with relatively large deviation with respect to the reference space bit of this satellite, this deviation has exceeded to be utilized with reference to almanac, the error range of Calculation of Satellite locus in the regular hour scope, and there is confidence level the reference locus of satellite, therefore execution in step S207, judge that the satellite navigation signals that receives is false navigation signal.
After step S207, can further carry out false navigation signal early warning, for example by the early warning pilot lamp glimmer alarm, stop location and/or time service information output.
The present embodiment is to judge that at above-mentioned the first embodiment satellite navigation signals is not on the basis of spurious signal, the locus of this satellite is calculated respectively in utilization with reference to almanac and current almanac, and the difference of these two result of calculations of comparison, if difference is excessive, surpassed the thresholding that arranges, the conclusion that can to obtain the current satellite navigation signals that receives be spurious signal.The falseness that this embodiment helps further to strengthen satellite navigation signals detects.
Fig. 3 has shown the structural representation of satellite navigation location receiver the first embodiment of the present invention.This receiver is except the composition with general navigation neceiver, also comprise for satellite navigation signals being carried out the false structure that detects forming, this satellite navigation location receiver comprises positioning unit 301, signal element 302, the first judging unit 303 and performance element 304.
Wherein, positioning unit 301 is used for carrying out initial alignment when receiver is started shooting, obtain the initial position of receiver according to positioning result.When the receiver initialization, the navigation message content that positioning unit 301 utilizes signal element 302 to obtain, carry out initial alignment, in order to guarantee the accuracy of initial alignment, generally need continuous several times to locate, for example be taken to few 10 continuous positioning results, the positioning result of these at least 10 initial alignments is carried out mean value computation, obtain thus the initial position of receiver.Positioning unit 301 also can be proofreaied and correct in the outside location parameter of determining of receiver by receipt source, determines the accuracy of initial position to improve positioning unit 301.
The first judging unit 303 is used for judging that according to the general location parameter this satellite is whether in the observation visual field of this receiver.This is because receiver is subject to geographic position of living in and figure of the earth structural limitations, it observes the visual field is limited, Navsat moves along satellite orbit with respect to the earth simultaneously, in a certain period, this satellite is just in time through the receiver observation visual field, and receiver is received the navigation signal that this satellite sends, so by reflecting that to this satellite general location calculation of parameter this satellite is in the observation visual field of receiver; If receive false satellite navigation signals, the general location parameter that just may calculate this satellite can not reflect in this satellite current observation visual field that is in receiver.Received on the one hand the navigation signal that this satellite sends, on the other hand by counter this satellite of releasing of this navigation signal not in the observation visual field of receiver, this self-contradictory presentation of results this navigation signal be not to derive from this satellite, therefore be false satellite navigation signals.The first judging unit 303 receives the result of calculation of 302 pairs of satellite general location parameters of signal elements, judges that thus this satellite is whether in the observation visual field of receiver.
Fig. 4 has shown the structural representation of satellite navigation location receiver the second embodiment of the present invention.Positioning unit 401 in Fig. 4, signal element 402, the first judging unit 403 have with Fig. 3 in corresponding positioning unit 301, signal element 302, technical characterictic that the first judging unit 303 is identical, repeat no more herein.The key distinction is, when judging this satellite when the first judging unit 403 according to satellite general location parameter and be in the observation visual field of receiver, need to further carry out falseness and detect.
Computing unit 405 is exactly when judgment result is that of the first judging unit 403 is, completes following computation process.At first, first calculating is satellite identity in the navigation message that receives according to signal element 402 and the reference almanac of storage, this satellite is carried out track calculate, and can obtain the reference locus of this satellite; Second calculating is satellite identity in the navigation message that receives according to signal element 402 and almanac wherein, is referred to as current almanac here about this almanac, calculates the current locus of this satellite.Then, the reference locus of satellite and the current locus of this satellite are compared, calculate exactly the distance between these two locus, be referred to as the error distance of these two locus here.
The second judging unit 406 will be compared by error distance and the threshold value that computing unit 405 obtains, and whether is used for the error in judgement distance greater than threshold value.
In performance element 404, carry out corresponding operation according to the judged result of the second judging unit 406.If error distance is greater than this threshold value, explanation calculates by the navigation message that receives current satellite spatial position is equipped with relatively large deviation with respect to the reference space bit of this satellite, this deviation has exceeded the error range of utilizing with reference to almanac Calculation of Satellite locus, and there is confidence level the reference locus of satellite, therefore can judge that the satellite navigation signals that receives is false navigation signal.If be less than or equal to threshold value, show that the satellite navigation signals that receives has higher confidence level, be actual signal, can receive navigation message wherein, and replace with reference to almanac, for late detection with current almanac.
By satellite navigation location receiver the first and second embodiment of the present invention, make this satellite navigation location receiver to detect based on the almanac in satellite navigation signals being carried out falseness, strengthened the anti-deception ability of this receiver.
Fig. 5 has shown the schematic flow sheet of the false satellite navigation signals detection method of the present invention the 3rd embodiment.The ephemeris that this embodiment mainly is based in navigation message carries out the falseness detection to the satellite navigation signals that receives.
In step S501, at first to obtain with reference to ephemeris from the satellite navigation signals that receives, and record this with reference to the update time of ephemeris.Herein, the called reference ephemeris refers to receiver differentiates to be the ephemeris that obtains real satellite navigation signals from receiving, and this ephemeris is along with passage of time constantly is updated and preserves.Simultaneously, the correct time that is updated with reference to ephemeris also goes on record.At the receiver start work initial stage, can utilize the true and false of some known accurate information judgement satellite navigation signals that receive, the accurate location of known receiver for example, whether the determined receiver location of satellite navigation signals that receives of check is correct thus, and then instead pushes away the true and false of ephemeris in the satellite navigation signals that receives.
Step S502 refers to that receiver constantly receives and the tracking satellite navigation signal, obtains current ephemeris from the satellite-signal that receives, and records the acquisition time of this current ephemeris, and calculating and with reference to time interval of update time of ephemeris.In step S501, the last update time with reference to ephemeris, use T
rxT is used in expression, and the acquisition time of current ephemeris in step S502
cxRepresent, calculate the time interval of these two times, i.e. T
cx-T
rx, it should meet the update frequency value of Navsat broadcast ephemeris, because Navsat always upgrades ephemeris with certain frequency, and keeps this update frequency constant.
Then, step S503 judges whether this time interval meets broadcast ephemeris update frequency value; When the determination result is NO, determine that satellite navigation signals is spurious signal.For example, this update frequency value is 2 hours/time, if the acquisition time of current ephemeris and the last time interval with reference to the update time of ephemeris equals ephemeris update frequency value, equal 2 hours as this time interval, or in its vicinity, as little error burst scope between 1 hour 58 minutes to 2 hours 2 minutes, show that the current ephemeris that obtains is normal; If this time interval obviously greater than or be significantly less than the update frequency value of broadcast ephemeris, show that current ephemeris derives from spurious signal, the satellite navigation signals that namely receives is spurious signal, after determining to be spurious signal, can also carry out false navigation signal early warning, for example by the early warning pilot lamp glimmer alarm, stop the location and (or) time service information output.
Fig. 6 is the schematic flow sheet of false detection method the 4th embodiment of satellite navigation signals of the present invention.Step S601 in Fig. 6, S602, S603, S607 have the technical characterictic identical with step S501, S502, S503 in Fig. 5, repeat no more herein.And in step S603, whether current ephemeris acquisition time and time interval with reference to ephemeris update time are met ephemeris update frequency value judging, is also to need further the satellite navigation signals that receives to be carried out falseness detection if judgment result is that.
Step S604 met on the basis of ephemeris update frequency value in the step S603 judgement time interval, further utilizes respectively with reference to ephemeris and current ephemeris the locus of satellite is calculated.Mainly complete following computation process.First calculating is according to the satellite identifier in the navigation message that receives, and at the reference ephemeris that step S601 obtains, this satellite is carried out track calculate, and can obtain the locus of this satellite, uses coordinate (X herein
sp, Y
sp, Z
sp) co-ordinates of satellite that obtains by the reference ephemeris of expression, and be referred to as satellite with reference to the locus.By as can be known aforementioned, because ephemeris upgrades comparatively fast, upgrade once as every 2 hours, the error precision of the satellite spatial position that utilizes before and after ephemeris upgrades that two different ephemeris computation obtain can be at meter level.Second calculating is according to the satellite identifier in the navigation message that receives and current ephemeris, and the locus of calculating this satellite is used coordinate (X herein
sf, Y
sf, Z
sf) co-ordinates of satellite that obtains by current ephemeris of expression, and be referred to as satellite current locus.Then, this satellite is compared with reference to locus and satellite current locus, calculate exactly the distance between these two locus, namely
Here be referred to as the error distance of these two locus.
In step S605, step the S604 error distance that obtains and the threshold value of presetting are compared judgement, for example threshold settings is 10 meters.if error distance is greater than threshold value, enter step S607, explanation calculates by the navigation message that receives current satellite spatial position is equipped with relatively large deviation with respect to the reference space bit of this satellite, this deviation has exceeded the error range of utilizing ephemeris to upgrade Calculation of Satellite locus, front and back, and be believable through the reference locus of the satellite differentiated, therefore the current locus of satellite is insincere, can judge that the satellite navigation signals that receives is false navigation signal, can also carry out false navigation signal early warning, for example by the alarm of glimmering of early warning pilot lamp, stop the location and (or) time service information output.
Step S606 is the situation of threshold value that is less than or equal to for error distance in step S605, can determine that the satellite navigation signals that receives is actual signal, replace existing with reference to ephemeris with the current ephemeris in the navigation message that receives, namely always replace existingly with reference to ephemeris as new reference star with current ephemeris, and acquisition time that will this current ephemeris is as the update time of new reference ephemeris.
The third and fourth embodiment of the false detection method of satellite navigation signals of the present invention is based on the update frequency to ephemeris in the satellite navigation signals that receives, and the distance error that ephemeris changes the satellite spatial position cause detects, and with threshold value relatively, thereby carry out detection and the early warning of spurious signal.The method has been utilized the characteristics rule of ephemeris, detects applicable to carrying out spurious signal in different satellite navigation systems, and applied range realizes that cost is low, has strengthened the anti-deception ability of satellite navigation location receiver.
Fig. 7 has shown the structural representation of the 3rd embodiment of satellite navigation location receiver of the present invention.This receiver also comprises for satellite navigation signals being carried out the false structure that detects forming except the composition with general navigation neceiver.
701 pairs of satellite navigation signals of signal element receive and follow the tracks of, and obtain the navigation message in satellite navigation signals.On the one hand, signal element 701 will be upgraded with reference to ephemeris from the satellite navigation signals that receives, and records this with reference to the update time of ephemeris.Herein, the called reference ephemeris refers to receiver differentiates to be the ephemeris that obtains real satellite navigation signals from receiving, and this ephemeris is along with passage of time constantly is updated and preserves.Simultaneously, the correct time that is updated with reference to ephemeris also goes on record.On the other hand, signal element 701 is also constantly obtained current ephemeris from the satellite navigation signals that receives, and record the acquisition time of this current ephemeris, but the satellite navigation signals that receives had both comprised the satellite navigation signals that the Navsat that newly enters the receiver visual field sends, also may receive false satellite navigation signals, therefore there is false possibility in current ephemeris.
For this reason, the first judging unit 702 according in signal element 701 with reference to update time of ephemeris, and the acquisition time of the current ephemeris from the satellite navigation signals that receives, calculate the interval of these two times, this time interval should meet the update frequency value of Navsat broadcast ephemeris, for example, this update frequency value is 2 hours/time.If the acquisition time of current ephemeris equals ephemeris update frequency value with interval with reference to the acquisition time of ephemeris, equal 2 hours as this time interval, or in its vicinity, as interval range between 1 hour 58 minutes to 2 hours 2 minutes, show that the current ephemeris that obtains is normal, meets the update frequency value of Navsat broadcast ephemeris; If this time interval obviously greater than or be significantly less than the update frequency value of ephemeris, show that this time interval do not meet the update frequency value of Navsat broadcast ephemeris, illustrate that current ephemeris derives from false navigation signal.
When between the first judging unit 702 judgements, the interval does not meet the update frequency value of Navsat broadcast ephemeris, this result is submitted to performance element 703, determine that by performance element 703 satellite navigation signals that receives is spurious signal.In addition, performance element 703 can also be made early warning, for example closes location and/or time service information output channel, opens sound alarm, pilot lamp alarm etc.
Fig. 8 has shown the structural representation of satellite navigation location receiver the 4th embodiment of the present invention.Signal element 801 in Fig. 8, the first judging unit 802 have with Fig. 7 in corresponding signal element 701, the technical characterictic that the first judging unit 702 is identical, repeat no more herein.Difference mainly is, when the acquisition time of the first current ephemeris of judging unit 802 judgement and time interval with reference to update time of ephemeris meet broadcast ephemeris update frequency value, can not be defined as spurious signal and carry out early warning by performance element 803, need to further carry out falseness and detect.
The second judging unit 805 will be compared by error distance and the threshold value that computing unit 804 obtains, and is used for judging that whether this error distance is greater than threshold value.Here the satellite spatial position that is obtained by ephemeris computation has higher precision, so this threshold value also has very high precision, and for example setting threshold value is 10 meters.
Then, in performance element 803, carry out corresponding operation according to the judged result of the second judging unit 805.If obtain error distance greater than threshold value at the second judging unit 805, explanation calculates by the navigation message that receives current satellite spatial position is equipped with relatively large deviation with respect to the reference space bit of this satellite, this deviation has exceeded the error range of utilizing with reference to ephemeris Calculation of Satellite locus, and there is confidence level the reference locus of satellite, therefore can judge that the satellite navigation signals that receives is false navigation signal, can also carry out early warning.Be less than or equal to threshold value if obtain error distance at the second judging unit 805, show that the satellite navigation signals that receives has higher confidence level, it is actual signal, can receive navigation message wherein, and replace with reference to ephemeris with current ephemeris, namely always replace existingly with reference to ephemeris as new reference star with current ephemeris, and acquisition time that will this current ephemeris is as the update time of new reference ephemeris, for late detection.
By satellite navigation location receiver the third and fourth embodiment of the present invention, make this satellite navigation location receiver to detect based on the ephemeris in satellite navigation signals being carried out falseness, strengthened the anti-deception ability of this receiver.
Fig. 9 has shown the schematic flow sheet of the false satellite navigation signals detection method of the present invention the 5th embodiment.Satellite clock and ephemeris that this embodiment mainly is based in navigation message carry out the falseness detection to the satellite navigation signals that receives.
Step S901 when receiver is started shooting, carries out initial alignment by this receiver, obtains the initial position of this receiver according to positioning result.Definite method and the step S101 shown in Fig. 1 of receiver initial position are similar, repeat no more.
Step S902 refers to that receiver constantly receives and the tracking satellite navigation signal, and further therefrom obtains current ephemeris and satellite clock.Then, based on satellite clock and the ephemeris in the satellite navigation signals that receives, and the initial position of receiver, need to complete following computation process.First calculating is according to the satellite ephemeris in the navigation message that receives, and the locus of Calculation of Satellite is with coordinate (X
sv, Y
sv, Z
sv) the expression satellite spatial position that obtains by ephemeris, then according to the initial position of the acquired receiver of step S901, with the initial position of coordinate (X, Y, Z) expression receiver, Calculation of Satellite is to the distance of receiver, namely
Result of calculation is referred to as star ground distance.Second calculating is based on the pseudo-random code ranging principle, receiver utilizes PN code delay locked loop (DLL, be called for short code tracking loop) the tracking pseudo-code of receiver is aimed at the pseudo-code of the satellite navigation signals that receives in time, with the tracking pseudo-code of receiver and the benchmark pseudo-code contrast of receiver, obtain the time difference Δ T of these two kinds of pseudo-codes again
1, represent the light velocity with c, obtain pseudorange ρ=c Δ T
1Consider again the impact of clock correction, namely according to the satellite clock T in the navigation message that receives
s, and the local clock T of receiver
r, obtained clock correction Δ T
2=T
r-T
s, with this clock correction, pseudorange ρ is revised, obtaining revised pseudorange is c(Δ T
1-Δ T
2), be referred to as to revise pseudorange.Then, then the star ground distance that obtains and the pseudorange that passes through the clock correction correction being calculated, is mainly the difference that obtains both, namely
Be referred to as error distance, get the absolute value of this error distance in application.
Step S903, whether the error in judgement distance is greater than threshold value, and threshold value for example is set as 30 meters.
If error distance greater than this threshold value, enters step S904, determine that this satellite navigation signals is spurious signal.This is because obtained the initial position accurately of receiver at step S901, if the satellite navigation signals that receives is real, revises so pseudorange and star ground apart from being basically identical, and perhaps both error is less than threshold value.Otherwise, due to the falseness of the falseness of satellite clock or satellite ephemeris can be reflected to revise pseudorange and star ground apart between larger error distance is arranged, explanation is spurious signal.And can carry out false navigation signal early warning, for example by the early warning pilot lamp glimmer alarm, stop location and/or time service information output.
Step S905 is less than or equal to the situation of threshold value for error distance in step S903, can determine that the satellite navigation signals that receives is actual signal, and store this ephemeris and satellite clock.
The 5th embodiment of the false detection method of satellite navigation signals of the present invention is based on to ephemeris and satellite clock in the satellite navigation signals that receives, calculate star ground distance and revise pseudorange, and distance error that will be both and threshold value comparison, thereby carry out detection and the early warning of spurious signal.The method has been utilized satnav principle and pseudo-random code ranging principle, detects applicable to carrying out spurious signal in different satellite navigation systems, and applied range realizes that cost is low, has strengthened the anti-deception ability of satellite navigation location receiver.
Figure 10 has shown the structural representation of satellite navigation location receiver the 5th embodiment of the present invention.This receiver also comprises for satellite navigation signals being carried out the false structure that detects forming except the composition with general navigation neceiver.
Wherein, positioning unit 1001, be used for when receiver start initialization, the navigation message content of utilizing signal element 1002 to obtain is carried out initial alignment to receiver, in order to guarantee the accuracy of initial alignment, generally need continuous several times to locate, for example be taken to few 10 continuous positioning results, these at least 10 positioning results are carried out mean value computation, obtain thus the initial position of this receiver.Positioning unit 1001 also can be proofreaied and correct in the outside location parameter of determining of this receiver by receipt source, determines the accuracy of initial position to improve positioning unit 1001.
Judging unit 1004 is used for and will be compared by error distance and the threshold value that computing unit 1003 obtains, and is used for judging that whether this error distance is greater than threshold value.This threshold value also has very high precision, and for example setting threshold value is 30 meters.
The false detection method embodiment of above-mentioned satellite navigation signals has introduced respectively by almanac, ephemeris and satellite clock in navigation message, satellite navigation signals is carried out falseness detect.In order further to improve the false probability that detects of satellite navigation signals, improve accuracy in detection, said method can be used in combination.Figure 11 has shown the schematic flow sheet of the 6th embodiment of the false detection method of satellite navigation signals of the present invention.
Step S1101 receives satellite navigation signals, resolve navigation message, obtain the parameters in the avionics literary composition, as ephemeris, almanac, satellite clock etc., then the parameter different according to these, carry out detecting based on the falseness of almanac at step S1102 respectively, specific implementation method is with reference to figure 1 and embodiment illustrated in fig. 2; Carry out detecting based on the falseness of ephemeris at step S1103, specific implementation method is with reference to figure 5 and embodiment illustrated in fig. 6; Carry out detecting based on the falseness of satellite clock and ephemeris at step S1104, specific implementation method is with reference to embodiment illustrated in fig. 9.And step S1102, S1103, S1104 can carry out to select a mode as required, also can be used in combination, and for example when step S1102 can not detect spurious signal, in order to improve detection probability, then enable step S1103 or S1104 detects.Two kinds of methods for example choosing again wherein detect simultaneously, perhaps use these three kinds of methods to detect simultaneously, strengthen accuracy in detection.Step S1105 comprehensively judges testing result according to the detection mode of step S1102, S1103, S1104, for example when step S1102, S1103, S1104 detect simultaneously, can adopt in step S1105 when wherein having at least two kinds of detection modes to obtain false detection results, just provide final effectively false detection results, be conducive to like this strengthen the false accuracy that detects.
By the way, the false detection method of satellite navigation signals of the present invention and receiver can be based on the navigation message contents in the satellite navigation signals that receives, locus by almanac, ephemeris, satellite clock Calculation of Satellite, star ground distance, revise pseudorange, error of calculation distance, and compare with reference thresholds, thereby the false information of the satellite navigation signals that receives of judgement, have method flexible and varied, have high accuracy and confidence level, realize the advantages such as cost is low.
The above is only embodiments of the invention; not thereby limit the scope of the claims of the present invention; every equivalent flow process conversion that utilizes instructions of the present invention and accompanying drawing content to do, or directly or indirectly be used in other relevant technical fields, all in like manner be included in scope of patent protection of the present invention.
Claims (10)
1. the false detection method of a satellite navigation signals, is characterized in that, described false detection method comprises:
When receiver is started shooting, carry out initial alignment by described receiver, obtain the initial position of described receiver according to positioning result;
Receive and the tracking satellite navigation signal, calculate the general location parameter of the satellite corresponding with described satellite navigation signals according to the reference almanac of described initial position and the storage of described receiver;
Judge that according to described general location parameter described satellite is whether in the observation visual field of described receiver; When the determination result is NO, determine that described satellite navigation signals is spurious signal.
2. the false detection method of satellite navigation signals according to claim 1, is characterized in that, described false detection method also comprises:
Judgment result is that when being, according to the described reference locus that calculates described satellite with reference to almanac, calculate the current locus of described satellite according to the current almanac in described satellite navigation signals, and calculate the reference locus of described satellite and the error distance between described current locus;
Judge that whether described error distance is greater than threshold value;
During greater than described threshold value, determine that described satellite navigation signals is spurious signal at described error distance.
3. the false detection method of satellite navigation signals according to claim 2, is characterized in that, described false detection method also comprises:
When described error distance is less than or equal to described threshold value, determine that described satellite navigation signals is actual signal, replace described with reference to almanac with described current almanac.
4. the false detection method of satellite navigation signals according to claim 1, is characterized in that, described general location parameter comprises position angle and the elevation angle.
5. the false detection method of satellite navigation signals according to claim 1, is characterized in that, described initial position is that the positioning result to the continuous several times initial alignment carries out the position that mean value computation obtains.
6. the false detection method of satellite navigation signals according to claim 5, it is characterized in that, described initial alignment carries out 10 times at least, the threshold condition of described mean value computation comprises: three-dimensional accuracy geometric factor＜3, satellite number 〉=5, the residual error of the least square iteration of positioning calculation＜0.01, the repeatedly longitude and latitude between the positioning result of initial alignment, elevation poor＜30 meter.
7. the false detection method of according to claim 5 or 6 described satellite navigation signals, it is characterized in that, after described initial position is determined, the location parameter of the outside described receiver of determining of described receiver is input to described receiver, so that described initial position is proofreaied and correct.
8. the false detection method of satellite navigation signals according to claim 3, is characterized in that, when the acquisition time of described current almanac and the interval of described update time with reference to almanac were less than or equal to 1 day, described threshold value was 1 kilometer; Greater than 1 day, and when being less than or equal to 5 days, described threshold value was 5 kilometers when the acquisition time of described current almanac and the interval of described update time with reference to almanac; During greater than 5 days, described threshold value is 10 kilometers when the acquisition time of described current almanac and the interval of described update time with reference to almanac.
9. a satellite navigation location receiver, is characterized in that, described receiver comprises:
Positioning unit is used for carrying out initial alignment when described receiver start, obtains the initial position of described receiver according to positioning result;
Signal element is used for receiving and the tracking satellite navigation signal, calculates the general location parameter of the satellite corresponding with described satellite navigation signals according to the reference almanac of described initial position and the storage of described receiver;
The first judging unit is used for judging that according to described general location parameter described satellite is whether in the observation visual field of described receiver;
Performance element is used for when the determination result is NO, determining that described satellite navigation signals is spurious signal at described the first judging unit.
10. satellite navigation location receiver according to claim 9, is characterized in that, described receiver also comprises:
Computing unit, be used for when judgment result is that of described the first judging unit is, according to the described reference locus that calculates described satellite with reference to almanac, calculate the current locus of described satellite according to the current almanac in described satellite navigation signals, and calculate described with reference to the error distance between locus and described current locus;
The second judging unit is used for judging that whether described error distance is greater than threshold value;
Described performance element is further used for during greater than described threshold value, determining that described satellite navigation signals is spurious signal at described error distance; And when described error distance is less than or equal to described threshold value, determine that described satellite navigation signals is actual signal, replace described with reference to almanac with described current almanac.
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