CN117554983A - Laser radar assisted GNSS non-line-of-sight signal screening method and device - Google Patents

Laser radar assisted GNSS non-line-of-sight signal screening method and device Download PDF

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CN117554983A
CN117554983A CN202311831081.5A CN202311831081A CN117554983A CN 117554983 A CN117554983 A CN 117554983A CN 202311831081 A CN202311831081 A CN 202311831081A CN 117554983 A CN117554983 A CN 117554983A
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satellite
representing
target
coordinate system
laser radar
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张文安
杨智强
杨旭升
史秀纺
付明磊
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Zhejiang University of Technology ZJUT
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Zhejiang University of Technology ZJUT
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/86—Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
    • G01C21/10—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration
    • G01C21/12—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning
    • G01C21/16—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation
    • G01C21/165—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation combined with non-inertial navigation instruments
    • G01C21/1652—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation combined with non-inertial navigation instruments with ranging devices, e.g. LIDAR or RADAR
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position
    • G01S19/43—Determining position using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/497—Means for monitoring or calibrating

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Electromagnetism (AREA)
  • Automation & Control Theory (AREA)
  • Position Fixing By Use Of Radio Waves (AREA)

Abstract

A laser radar assisted GNSS non-line-of-sight signal screening method and device, the device includes: s1: the target receives the epoch satellite ephemeris and calculates the coordinates of the satellite under the navigation coordinate system; s2: acquiring a laser radar data frame, adding the processed data into a cache, and constructing a laser radar local point cloud map under a navigation coordinate system at the moment t; s3: obtaining the prior position of the target, and calculating heading angle information a between the target and the satellite i i And pitch angle information e i The method comprises the steps of carrying out a first treatment on the surface of the S4: traversing satellites, searching point cloud information from a target to a satellite i on a local map, and screening the satellite if the number of point clouds larger than a threshold exists between the target and the satellite i in the searching rangeA satellite i, otherwise, traversing the next satellite until the traversing of the satellite is completed; s5: and (3) carrying out position correction on the observed quantity and the priori information of the screened satellite group, carrying out measurement updating to obtain corrected position information, returning to S1 when satellite and laser radar data exist at the next moment, and ending if not.

Description

Laser radar assisted GNSS non-line-of-sight signal screening method and device
Technical Field
The invention belongs to the technical field of positioning, and particularly relates to a laser radar assisted GNSS (Global Navigation Satellite System, GNSS) non-line-of-sight signal screening method and device.
Background
GNSS is an air-based radio navigation positioning system that can provide all-weather 3-dimensional coordinates and velocity and time information to a user at any location on the earth's surface or near-earth space. There are a number of factors that affect the positioning accuracy of a GNSS, including satellite orbit error, ionosphere and troposphere delays, and Non-Light-of-Sight (NLOS) satellite signals, among others. Particularly, in an occlusion environment, NLOS satellite signals caused by occlusion factors such as an urban high-rise environment seriously affect positioning results. The NLOS signals are GNSS signals arriving at a receiver due to reflection or diffraction of a building or other obstacles, and their propagation paths are complex, which results in that the pseudorange measurement contains a large number of noise items which cannot be modeled, thereby affecting the positioning accuracy. Therefore, the screening of NLOS signals is an important premise for improving the positioning accuracy of GNSS.
Typically, the screening of NLOS signals is a method based on residual sequence detection. The method comprises the steps of receiver autonomous integrity monitoring (Receiver autonomous integrity monitoring, RAIM), wherein satellite signals possibly with anomalies are judged one by calculating post-verification residual errors of satellite pseudo-ranges, so that the purpose of screening NLOS signals is achieved. However, when a large number of NLOS signals are present, RAIM requires multiple rounds of detection, and the computational complexity is high. Another is an NLOS signal detection method based on a three-dimensional city model (3 d map aid, 3 dma), which checks the availability of measurement signals by shadow matching and predicts satellite visibility from the three-dimensional city model using building boundaries, thereby improving satellite positioning accuracy. However, 3DMA is limited in that it relies on a priori knowledge of the three-dimensional city model and requires high computational costs to distinguish LOS signals from NLOS signals. This results in insufficient generalization capability and computational inefficiency of the method. Therefore, no real-time effective NLOS signal screening method is available at present to improve the positioning accuracy and robustness of the GNSS system in the shielding environment.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a laser radar assisted GNSS non-line-of-sight signal screening method and device so as to improve positioning accuracy and robustness in a shielding environment.
The first aspect of the invention is: a lidar assisted GNSS (Global Navigation Satellite System, GNSS) non-line-of-sight signal screening method comprising the steps of:
step S1: the target receives the satellite ephemeris of the current epoch, and calculates the coordinates of the satellite under the navigation coordinate system;
step S2: obtaining a laser radar data frame, carrying out distortion treatment, adding the treated data into a buffer, and constructing a laser radar local point cloud map M under a navigation coordinate system at the moment t t ；
Step S3: obtaining a priori position of the target by using an inertial measurement unit (Inertial Measurement Unit, IMU) and calculating heading angle information a between the target and the satellite i in a navigation coordinate system i And pitch angle information e i ；
Step S4: traversing all satellites in time t and locating the satellite on a local map M t Searching for point cloud information from the target to the satellite i. If the number of point clouds larger than the threshold exists between the target and the satellite i in the searching range, screening the satellite i, otherwise, traversing the next satellite until all satellites are traversed at the moment t;
step S5: and carrying out position correction on the observed quantity of the screened satellite group and priori information provided by the IMU mechanical arrangement. And (3) carrying out measurement updating through double-difference pseudo-range observation and double-difference carrier phase observation to obtain corrected position information, returning to the step S1 when satellite and laser radar data exist at the next moment, and ending the step otherwise.
Wherein, the step S1 comprises the following substeps:
s11: the target obtains satellite ephemeris of the satellite i through a receiver, and coordinates of the satellite i under a navigation coordinate system are obtained through satellite ephemeris calculationWherein the superscript n represents a navigation coordinate system; subscript i represents the ith satellite; the subscripts e, n, u denote the components of the coordinates in the east, north, and sky, respectively, of the navigation system.
Wherein, the step S2 comprises the following substeps:
s21: acquiring radar data of a current frame, performing de-distortion processing on the acquired radar data, traversing IMU data between start and stop moments of the current laser frame, calculating rotation translation transformation from each point to a start point of the point cloud of each frame according to a time stamp of the point in the point cloud of each frame, and transforming each point to a coordinate system of the start point;
s22: and storing the undistorted radar data frames into a buffer space with the size of 20, storing the latest 20 frames of radar data in the buffer space, and constructing a local radar point cloud map by utilizing the point cloud data in the buffer space of the radar frames.
Wherein, the step S3 comprises the following substeps:
s31: let the priori position information of IMU in navigation coordinate system be p n ＝[p e ,p n ,p u ] T Using the coordinates of satellite i in the navigation system obtained in step S1Calculating a priori position p n Vector v with satellite i n :
Thus there is a unit vector
Wherein the superscript n represents a navigation coordinate system; subscript u represents a unit vector; v n The expression vector v n Is a die length of (2); subscripts e, n, u represent the components of the coordinates on the east, north, and sky of the navigation system, respectively;
s32: by unit vectorCalculating the course angle between the carrier and the satellite under the navigation system:
pitch angle:
obtaining a course angle a from a target to a satellite i under a navigation system by traversing each satellite i And pitch angle information e i And providing search information for subsequent searching of the radar local point cloud map.
Wherein, the step S4 comprises the following substeps:
s41: at time t, radar local point cloud map M t Heading angle a of target to satellite i i And pitch angle e i Lei Dadian cloud search radius R s NLOS signal inspection threshold T t Search range R f ；
S42: will M t The data is converted into kdTare form to be stored, and kdTare is helpful for improving the searching efficiency of the radar point cloud. Coordinates of the center of the target radar under the navigation coordinate system at the existing time t:
wherein the superscript L denotes radar, in +.>The satellite i course angle a obtained in the step S4 is utilized as the origin point i Information and pitch angle information e i Searching is carried out, and the k-th round of searching point updating is carried out by giving a fixed searching step delta d:
wherein the subscript k represents the kth round of search;
s43: kdTrare search is performed on the new search point if the radius R is searched for in the kth round s Number of points P obtained in k >T t Then the satellite is judged to be the NLOS signal satellite to screen out if the obstacle exists between the carrier and the satellite, otherwise, when the total search radius kDeltad is the same>R f Determining the satellite as an LOS signal;
s44: repeating the processes S42 and S43 until all satellite traversals at the moment t are completed, and obtaining a screened satellite group S l 。
Wherein, the step S5 comprises the following substeps:
s51: after screening satellite group S l Satellite group S with reference station b The common-view satellite is searched, and a main satellite is searched in each satellite system, wherein the main satellite adopts a satellite group S l A satellite with the highest pitch angle;
s52: the GNSS receiver has the following formula:
wherein, gamma represents the wavelength of the corresponding frequency point;representing carrier phase observations; the subscript r represents the receiver; t represents the time t; superscript s represents satellite s; />Representing the distance of the receiver from satellite s; c L Representing the speed of light, delta r,t Representing receiver clock skew;representing the clock error of satellite s; />Represents ionospheric delay; />Represents tropospheric delay; />Is carrier phase offset;representative representation carrier phase correction terms including antenna phase offset and variation, station displacement due to earth tides, and relative correction of satellite clocks; />Representing pseudo-range observations; psi phi type r,0,t Representing an initial phase of a receiver local oscillator; />Representing an initial phase of a navigation signal transmitted from a satellite; />Integer ambiguity representing carrier phase; />Representing multipath interference, non-line-of-sight signals, receiver noise, antenna delays, etc.;
s53: double-difference pseudo-range measurement equation:
wherein,and->Pseudo-range observations representing satellites s and a main satellite w received by a reference station; the superscript sw indicates that a double difference is made between the satellite s and the satellite w; subscript b represents the value received by the reference station at time t; the subscript r denotes the receiver; subscript DD represents the double difference observation. High elevation satellite signals typically have less non-line-of-sight signal interference and relatively less multipath effects, and therefore are more prone to selecting high elevation satellites as the primary satellite, which is marked as superscript w. By doing double difference solution +.>Eliminating an atmospheric interference term and a clock error interference term;
s54: dual differential carrier phase measurement equation:
wherein,and->Represents the observed value of the carrier phase received by the reference station, and the interference of the atmospheric interference term and the clock error is also eliminated after the carrier phase double-difference is solved, but +.>The method also comprises double-difference integer ambiguity;
s55: the existing double-difference pseudo-range observation equation:
wherein p is r,t Representing the position of the receiver at time t in the ECEF coordinate system; subscripts x, y, z denote the x-axis, y-axis, z-axis components, respectively, in the ECEF coordinate system;representing the position of satellite s at time t; />Representing the position of satellite w at time t; p is p b Representing the position of the reference station; />Representing noise terms associated with the pseudoranges. Thus, the error factor of the double difference pseudorange may be expressed as:
wherein,representation->Is a covariance of (2);
s56: there is a double difference carrier phase observation equation:
wherein,represents->Is a noise related to (a); />Representing double difference integer ambiguity; there is thus an error factor for the double difference carrier phase:
representation->Is a covariance matrix of (a);
s57: inertial navigation error factor:
wherein the superscript INS represents an INS factor; v t-1 Representing the velocity of the target in the ECEF coordinate system;representing acceleration of the target in the ECEF coordinate system at time t; Δt represents the time interval between two adjacent INS factors; />A covariance matrix representing INS factors;
s58: there is thus an objective function:
wherein the variable χ * Representing an optimal estimate of the state set; p is p r,t And v r,t Representing the position and speed of the target t moment under an ECEF coordinate system;representing the double difference ambiguity of the satellite group at time t. Therefore, by solving the objective function, the floating solution of the GNSS-RTK screened by the NLOS satellite in the current epoch can be obtained, the fixed solution is estimated by using an ambiguity fixing algorithm, and finally the corrected position information screened by the NLOS signal is obtained. And returning to the step S1 when satellite and laser radar data exist at the next moment, and ending the step otherwise.
A second aspect of the present invention relates to a laser radar assisted GNSS non-line-of-sight signal screening apparatus, comprising a memory and one or more processors, wherein executable code is stored in the memory, and the one or more processors are configured to implement the laser radar assisted GNSS non-line-of-sight signal screening method of the present invention when executing the executable code.
The invention relates to a computer readable storage medium, which stores a program which, when being executed by a processor, realizes the GNSS non-line-of-sight signal screening method assisted by the laser radar.
The working principle of the invention is as follows: and constructing a local point cloud map of the surrounding environment of the target by using a laser radar, calculating the position of the satellite relative to the target, and judging as an NLOS signal if the number of point clouds of the connecting line between the satellite and the target is larger than a threshold value.
The invention has the advantages that: the NLOS signal screening method based on laser radar assistance can screen NLOS signals in urban shielding and other environments more quickly and efficiently.
Drawings
The invention is described in further detail below with reference to the attached drawing figures, wherein:
FIG. 1 is a schematic diagram of a non-line-of-sight signal of the present invention.
Fig. 2 is a flow chart of the method of the present invention.
FIG. 3 is a block flow diagram of GNSS non-line-of-sight signal screening according to the present invention.
Fig. 4 is a schematic diagram of the present invention for filtering NLOS satellite signals by means of a lidar local map.
Fig. 5 is a diagram showing the error in the east direction of embodiment 2 of the present invention.
Fig. 6 is a diagram illustrating the north orientation error in embodiment 2 of the present invention.
Detailed Description
The technical scheme of the invention is further described below with reference to the accompanying drawings.
Example 1
1-4, this embodiment requires (1) an RTK reference station, (2) a GNSS receiver, (3) a lidar, (4) an IMU, (5) network RTK services, and (6) a satellite antenna. The (1) RTK reference station is used for broadcasting RTK differential information and transmitting the information through the (5); the (2) GNSS receiver is used for processing GNSS signals; (3) the method comprises the steps of constructing a laser radar local map; the (4) is used for carrying out dead reckoning, and the GNSS information obtained in the (2) is fused and positioned; said (5) being operative to transmit RTK reference station information; said (6) is used for receiving GNSS signals
A lidar assisted GNSS (Global Navigation Satellite System, GNSS) non-line-of-sight signal screening method comprising the steps of:
step S1: the target receives the satellite ephemeris of the current epoch, and calculates the coordinates of the satellite under the navigation coordinate system;
step S2: obtaining a laser radar data frame, carrying out distortion treatment, adding the treated data into a buffer, and constructing a laser radar local point cloud map M under a navigation coordinate system at the moment t t ；
Step S3: obtaining a priori position of the target by using an inertial measurement unit (Inertial Measurement Unit, IMU) and calculating heading angle information a between the target and the satellite i in a navigation coordinate system i And pitch angle information e i ；
Step S4: traversing all satellites in time t and locating the satellite on a local map M t Searching for point cloud information from the target to the satellite i. If the number of point clouds larger than the threshold exists between the target and the satellite i in the searching range, screening the satellite i, otherwise, traversing the next satellite until all satellites are traversed at the moment t;
step S5: and carrying out position correction on the observed quantity of the screened satellite group and priori information provided by the IMU mechanical arrangement. And (3) carrying out measurement updating through double-difference pseudo-range observation and double-difference carrier phase observation to obtain corrected position information, returning to the step S1 when satellite and laser radar data exist at the next moment, and ending the step otherwise.
Wherein, the step S1 comprises the following substeps:
s11: the target obtains satellite ephemeris of the satellite i through a receiver, and coordinates of the satellite i under a navigation coordinate system are obtained through satellite ephemeris calculationWherein the superscript n represents a navigation coordinate system; subscript i represents the ith satellite; the subscripts e, n, u denote the components of the coordinates in the east, north, and sky, respectively, of the navigation system.
Wherein, the step S2 comprises the following substeps:
s21: acquiring radar data of a current frame, performing de-distortion processing on the acquired radar data, traversing IMU data between start and stop moments of the current laser frame, calculating rotation translation transformation from each point to a start point of the point cloud of each frame according to a time stamp of the point in the point cloud of each frame, and transforming each point to a coordinate system of the start point;
s22: and storing the undistorted radar data frames into a buffer space with the size of 20, storing the latest 20 frames of radar data in the buffer space, and constructing a local radar point cloud map by utilizing the point cloud data in the buffer space of the radar frames.
Wherein, the step S3 comprises the following substeps:
s31: let the priori position information of IMU in navigation coordinate system be p n ＝[p e ,p n ,p u ] T Using the coordinates of satellite i in the navigation system obtained in step S1Calculating a priori position p n Vector v with satellite i n :
Thus there is a unit vector
Wherein the superscript n represents a navigation coordinate system; subscript u represents a unit vector; v n The expression vector v n Is a die length of (2); subscripts e, n, u represent the components of the coordinates on the east, north, and sky of the navigation system, respectively;
s32: by unit vectorCalculating the course angle between the carrier and the satellite under the navigation system:
pitch angle:
obtaining a course angle a from a target to a satellite i under a navigation system by traversing each satellite i And pitch angle information e i And providing search information for subsequent searching of the radar local point cloud map.
Wherein, the step S4 comprises the following substeps:
s41: at time t, radar local point cloud map M t Heading angle a of target to satellite i i And pitch angle e i Lei Dadian cloud search radius R s NLOS signal inspection threshold T t Search range R f ；
S42: will M t Converted to kdTrae formAccording to the storage, kdTrae is helpful to improve the searching efficiency of the radar point cloud. Coordinates of the center of the target radar under the navigation coordinate system at the existing time t:
wherein the superscript L denotes radar, in +.>The satellite i course angle a obtained in the step S4 is utilized as the origin point i Information and pitch angle information e i Searching is carried out, and the k-th round of searching point updating is carried out by giving a fixed searching step delta d:
wherein the subscript k represents the kth round of search;
s43: kdTrare search is performed on the new search point if the radius R is searched for in the kth round s Number of points P obtained in k >T t Then the satellite is judged to be the NLOS signal satellite to screen out if the obstacle exists between the carrier and the satellite, otherwise, when the total search radius kDeltad is the same>R f Determining the satellite as an LOS signal;
s44: repeating the processes S42 and S43 until all satellite traversals at the moment t are completed, and obtaining a screened satellite group S l 。
Wherein, the step S5 comprises the following substeps:
s51: after screening satellite group S l Satellite group S with reference station b Finding common view satellites in each satelliteSearching a main satellite in the system, wherein the main satellite adopts a satellite group S l A satellite with the highest pitch angle;
s52: the GNSS receiver has the following formula:
wherein lambda represents the wavelength of the corresponding frequency point;representing carrier phase observations; the subscript r represents the receiver; t represents the time t; superscript s represents satellite s; />Representing the distance of the receiver from satellite s; c L Representing the speed of light, delta r,t Representing receiver clock skew; />Representing the clock error of satellite s; />Represents ionospheric delay; />Represents tropospheric delay; />Is carrier phase offset; />Representative representation carrier phase correction terms including antenna phase offset and variation, station displacement due to earth tides, and relative correction of satellite clocks; />Representing pseudo-range observations; psi phi type r,0,t Representing an initial phase of a receiver local oscillator; />Representing an initial phase of a navigation signal transmitted from a satellite; />Integer ambiguity representing carrier phase; />Representing multipath interference, non-line-of-sight signals, receiver noise, antenna delays, etc.;
s53: double-difference pseudo-range measurement equation:
wherein,and->Pseudo-range observations representing satellites s and a main satellite w received by a reference station; the superscript sw indicates that a double difference is made between the satellite s and the satellite w; subscript b represents the value received by the reference station at time t; the subscript r denotes the receiver; subscript DD represents the double difference observation. High elevation satellite signals typically have less non-line-of-sight signal interference and relatively less multipath effects, and therefore are more prone to selecting high elevation satellites as the primary satellite, which is marked as superscript w. By doing double difference solution +.>Eliminating an atmospheric interference term and a clock error interference term;
s54: dual differential carrier phase measurement equation:
wherein,and->Represents the observed value of the carrier phase received by the reference station, and the interference of the atmospheric interference term and the clock error is also eliminated after the carrier phase double-difference is solved, but +.>The method also comprises double-difference integer ambiguity;
s55: the existing double-difference pseudo-range observation equation:
wherein p is r,t Representing the position of the receiver at time t in the ECEF coordinate system; subscripts x, y, z denote the x-axis, y-axis, z-axis components, respectively, in the ECEF coordinate system;representing the position of satellite s at time t; />Representing the position of satellite w at time t; p is p b Representing the position of the reference station; />Representing noise terms associated with the pseudoranges. Thus, the error factor of the double difference pseudorange may be expressed as:
wherein,representation->Is a covariance of (2);
s56: there is a double difference carrier phase observation equation:
wherein,represents->Is a noise related to (a); />Representing double difference integer ambiguity; there is thus an error factor for the double difference carrier phase:
representation->Is a covariance matrix of (a);
s57: inertial navigation error factor:
wherein the superscript INS represents an INS factor; v t-1 Representing the velocity of the target in the ECEF coordinate system;representing acceleration of the target in the ECEF coordinate system at time t; Δt represents the time interval between two adjacent INS factors; />A covariance matrix representing INS factors;
s58: there is thus an objective function:
wherein the variable χ * Representing an optimal estimate of the state set; p is p r,t And p is as follows r,t Representing the position and speed of the target t moment under an ECEF coordinate system;representing the double difference ambiguity of the satellite group at time t. Therefore, by solving the objective function, the floating solution of the GNSS-RTK screened by the NLOS satellite in the current epoch can be obtained, the fixed solution is estimated by using an ambiguity fixing algorithm, and finally the corrected position information screened by the NLOS signal is obtained. And returning to the step S1 when satellite and laser radar data exist at the next moment, and ending the step otherwise.
Example 2:
the embodiment shows a specific data acquisition and experiment process, wherein a satellite receiver is used for acquiring a group of satellite data in a city semi-shielding environment, and a laser radar is used for acquiring point cloud data. The satellite data is subjected to GNSS single-point positioning (Single Point positioning, SPP) result ratio by using satellites of three satellite systems, namely a global positioning system (Global Positioning System, GPS), a Chinese Beidou satellite navigation system (Beidou Navigation Satellite System, BDS) and a Galileo satellite navigation system (Galileo satellite navigation syste, GAL). Where (Weighted least square, WLS) represents the least squares algorithm, the factor graph (Factor Graph Optimization, FGO) represents the factor graph algorithm, and FGO-NLOS represents the factor graph algorithm after NLOS signal screening.
Example 3
The embodiment relates to a laser radar assisted GNSS non-line-of-sight signal screening device, which comprises a memory and one or more processors, wherein executable codes are stored in the memory, and the one or more processors are used for realizing the laser radar assisted GNSS non-line-of-sight signal screening method of the embodiment 1 when executing the executable codes.
Example 4
The present embodiment relates to a computer-readable storage medium having a program stored thereon, which when executed by a processor, implements the lidar-assisted GNSS non-line-of-sight signal screening method of embodiment 1.
The embodiments of the present invention are described in a progressive manner, and the same and similar parts of the embodiments are all referred to each other, and each embodiment is mainly described in the differences from the other embodiments. In particular, for system embodiments, since they are substantially similar to method embodiments, the description is relatively simple, as relevant to see a section of the description of method embodiments.
The foregoing is merely exemplary of the present invention and is not intended to limit the present invention. Various modifications and variations of the present invention will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are to be included in the scope of the claims of the present invention.

Claims (8)

1. A laser radar assisted GNSS non-line-of-sight signal screening method comprises the following steps:
step S1: the target receives the satellite ephemeris of the current epoch, and calculates the coordinates of the satellite under the navigation coordinate system;
step S2: obtaining a laser radar data frame, carrying out distortion treatment, adding the treated data into a buffer, and constructing a laser radar local point cloud map M under a navigation coordinate system at the moment t t ；
Step S3: obtaining a priori position of the target by using an inertial measurement unit (Inertial Measurement Unit, IMU) and calculating heading angle information a between the target and the satellite i in a navigation coordinate system i And pitch angle information e i ；
Step S4: traversing all satellites in time t and locating the satellite on a local map M t Searching point cloud information from a target to a satellite i; if the number of point clouds larger than the threshold exists between the target and the satellite i in the searching range, screening the satellite i, otherwise, traversingThe next satellite is traversed until all satellites are traversed at time t;
step S5: position correction is carried out on the observed quantity of the screened satellite group and priori information provided by IMU mechanical arrangement; and (3) carrying out measurement updating through double-difference pseudo-range observation and double-difference carrier phase observation to obtain corrected position information, returning to the step S1 when satellite and laser radar data exist at the next moment, and ending the step otherwise.
2. The method for laser radar assisted GNSS non-line-of-sight signal screening according to claim 1, wherein in step S1, the target obtains satellite ephemeris of satellite i through a receiver, and coordinates of satellite i under a navigation coordinate system are obtained through satellite ephemeris calculationWherein the superscript n represents a navigation coordinate system; subscript i represents the ith satellite; the subscripts e, n, u denote the components of the coordinates in the east, north, and sky, respectively, of the navigation system.
3. The method for laser radar assisted GNSS non-line-of-sight signal screening according to claim 1, wherein step S2 comprises the sub-steps of:
s21: acquiring radar data of a current frame, performing de-distortion processing on the acquired radar data, traversing IMU data between start and stop moments of the current laser frame, calculating rotation translation transformation from each point to a start point of the point cloud of each frame according to a time stamp of the point in the point cloud of each frame, and transforming each point to a coordinate system of the start point;
s22: and storing the undistorted radar data frames into a buffer space with the size of 20, storing the latest 20 frames of radar data in the buffer space, and constructing a local radar point cloud map by utilizing the point cloud data in the buffer space of the radar frames.
4. The method for laser radar assisted GNSS non-line-of-sight signal screening according to claim 1, wherein step S3 comprises the sub-steps of:
s31: let the priori position information of IMU in navigation coordinate system be p n ＝[p e ,p n ,p u ] T Using the coordinates of satellite i in the navigation system obtained in step S1Calculating a priori position p n Vector v with satellite i n :
Thus there is a unit vector
Wherein the superscript n represents a navigation coordinate system; subscript u represents a unit vector; v n The expression vector v n Is a die length of (2); subscripts e, n, u represent the components of the coordinates on the east, north, and sky of the navigation system, respectively;
s32: by unit vectorCalculating the course angle between the carrier and the satellite under the navigation system:
pitch angle:
navigation system obtained by traversing each satelliteHeading angle a of lower target to satellite i i And pitch angle information e i And providing search information for subsequent searching of the radar local point cloud map.
5. The method for laser radar assisted GNSS non-line-of-sight signal screening according to claim 1, wherein said step S4 comprises the sub-steps of:
s41: at time t, radar local point cloud map M t Heading angle a of target to satellite i i And pitch angle e i Lei Dadian cloud search radius R s NLOS signal inspection threshold T t Search range R f ；
S42: will M t The data are converted into kdToe form for storage, and kdToe is helpful for improving the searching efficiency of the radar point cloud; coordinates of the center of the target radar under the navigation coordinate system at the existing time t:
wherein the superscript L denotes radar, in +.>The satellite i course angle a obtained in the step S4 is utilized as the origin point i Information and pitch angle information e i Searching is carried out, and the k-th round of searching point updating is carried out by giving a fixed searching step delta d:
wherein the subscript k represents the kth round of search;
s43: kdTrare search is performed on the new search point if the radius R is searched for in the kth round s Number of points P obtained in k >T t Then the satellite is judged to be the NLOS signal satellite to screen out if the obstacle exists between the carrier and the satellite, otherwise, when the total search radius kDeltad is the same>R f Determining the satellite as an LOS signal;
s44: repeating the processes S42 and S43 until all satellite traversals at the moment t are completed, and obtaining a screened satellite group S l 。
6. The method for laser radar assisted GNSS non-line-of-sight signal screening according to claim 1, wherein said step S5 comprises the sub-steps of:
s51: after screening satellite group S l Satellite group S with reference station b The common-view satellite is searched, and a main satellite is searched in each satellite system, wherein the main satellite adopts a satellite group S l A satellite with the highest pitch angle;
s52: the GNSS receiver has the following formula:
wherein lambda represents the wavelength of the corresponding frequency point;representing carrier phase observations; the subscript r represents the receiver; t represents the time t; superscript s represents satellite s；/>Representing the distance of the receiver from satellite s; c L Representing the speed of light, delta r,t Representing receiver clock skew; />Representing the clock error of satellite s; />Represents ionospheric delay; />Represents tropospheric delay; />Is carrier phase offset; />Representative representation carrier phase correction terms including antenna phase offset and variation, station displacement due to earth tides, and relative correction of satellite clocks; />Representing pseudo-range observations; psi phi type r,0,t Representing an initial phase of a receiver local oscillator; />Representing an initial phase of a navigation signal transmitted from a satellite; />Integer ambiguity representing carrier phase; />Representing multipath interferenceNon-line-of-sight signals, receiver noise, antenna delays, etc.;
s53: double-difference pseudo-range measurement equation:
wherein,and->Pseudo-range observations representing satellites s and a main satellite w received by a reference station; the superscript sw indicates that a double difference is made between the satellite s and the satellite w; subscript b represents the value received by the reference station at time t; the subscript r denotes the receiver; subscript DD represents double difference observations; high elevation satellite signals typically have less non-line-of-sight signal interference and relatively less multipath effects, and therefore are more prone to selecting high elevation satellites as the primary satellite, labeled as superscript w; by doing double difference solutionEliminating an atmospheric interference term and a clock error interference term;
s54: dual differential carrier phase measurement equation:
wherein,and->Representing the carrier phase observed value received by the reference station, the carrier phase double-difference is solved to eliminate the interference of the atmospheric interference term and the clock difference/>The method also comprises double-difference integer ambiguity;
s55: the existing double-difference pseudo-range observation equation:
wherein p is r,t Representing the position of the receiver at time t in the ECEF coordinate system; subscripts x, y, z denote the x-axis, y-axis, z-axis components, respectively, in the ECEF coordinate system;representing the position of satellite s at time t; />Representing the position of satellite w at time t; p is p b Representing the position of the reference station; />Representing noise terms associated with the pseudoranges; thus, the error factor of the double difference pseudorange may be expressed as:
wherein,representation->Is a covariance of (2);
s56: there is a double difference carrier phase observation equation:
wherein,represents->Is a noise related to (a); />Representing double difference integer ambiguity; there is thus an error factor for the double difference carrier phase:
representation ofIs a covariance matrix of (a);
s57: inertial navigation error factor:
wherein the superscript INS represents an INS factor; v t-1 Representing the velocity of the target in the ECEF coordinate system;representing acceleration of the target in the ECEF coordinate system at time t; Δt represents the time interval between two adjacent INS factors; />A covariance matrix representing INS factors;
s58: there is thus an objective function:
wherein the variable χ * Representing an optimal estimate of the state set; p is p r,t And v r,t Representing the position and speed of the target t moment under an ECEF coordinate system;representing double-difference ambiguity of the satellite group at the time t; therefore, by solving the objective function, the GNSS-RTK floating solution in the current epoch after NLOS satellite screening can be obtained, and ambiguity-fixed calculation is usedEstimating a fixed solution by a method to finally obtain corrected position information screened by NLOS signals; and returning to the step S1 when satellite and laser radar data exist at the next moment, and ending the step otherwise.
7. A lidar assisted GNSS non-line-of-sight signal screening apparatus comprising a memory and one or more processors, the memory having executable code stored therein, the one or more processors configured to implement the lidar assisted GNSS non-line-of-sight signal screening method of any of claims 1-6 when the executable code is executed.
8. A computer readable storage medium, having stored thereon a program which, when executed by a processor, implements the lidar assisted GNSS non-line of sight signal screening method of any of claims 1 to 6.
CN202311831081.5A 2023-12-27 2023-12-27 Laser radar assisted GNSS non-line-of-sight signal screening method and device Pending CN117554983A (en)

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