Background
The HD Map is a Map specially used for unmanned driving, the application of a high-precision Map is more and more important for the unmanned driving, and a high-precision road network is the most important composition content in the high-precision Map. With the development of intelligent transportation and the development of heat in ADAS, HD map (High Definition map) has attracted great attention in both academic and industrial circles (documents 1 to 5). The HD map can provide refined map information to assist the intelligent vehicle in realizing high-precision positioning (documents 6 to 8), can solve the problem of sensor failure under specific conditions, makes up for the deficiency of environmental sensing equipment, and effectively reduces the difficulty of intelligent vehicle sensing (documents 9 to 11); according to the prior knowledge of the map and the dynamic traffic information, an optimal driving path and a reasonable driving strategy are given based on global path planning (documents 12 to 14), active safety of driving vehicles is effectively realized, and the complexity of vehicle driving is reduced (document 15). Therefore, the generation of the HD map becomes very important, and the HD map is currently in a great demand stage (document 16). Road network data is an expression of a real-world road model, and high definition road network is an important component of the HD map.
However, currently, studies on automatic generation of a high-precision road network are not many, which focus on both road extraction and link extraction.
The research on the generation of high-precision road networks mainly focuses on the extraction of road networks (documents 17 to 19), the generation of high-precision road segments (documents 20 and 21), the extraction of high-precision intersections (document 22), and the like, by using crowdsourcing or smart car equipment. In the research on the model of the high-precision road network, research is mainly focused on the format of the expression of the high-precision road network (document 23), the expression of the high-precision intersection (document 24), the road model (documents 25 and 26) and the like, but few people pay attention to the automatic generation of the topological correlation between the lane and the road section. Some studies have been made on automatic generation of automatic generation topological relations of a road network, and the main methods include merging intersections of different layers (document 27), using point correlation (document 28), and using a Hidden Markov Model (HMM) map matching (document 29). However, these studies are not based on topology extraction of a lane-level road network, and much manual methods are used for topology extraction of the lane-level road network.
HD map data is generally centimeter-level localization of approximation (document 30), and automatic generation of a high-precision road network is receiving attention from students more and more. The objects served by the high-precision map include not only the existing ADAS system but also an unmanned system, an auxiliary safety system, a vehicle road coordination system, and the like.
On the aspect of model expression of a high-precision road network, a plurality of relevant researches are carried out on a learner who has already learned lane extraction and model at present. And Gi-Poong et al uses piece wise polymers to simulate the lanes, so that the storage efficiency of the road network is improved. The lanes are expressed by an a third-order concrete similar to an approximated faster chochochochochochochochochoid spline, and the curve of the turn at the intersection is expressed by the cubic Catmull-Rom spline (document 17), both of which can be modeled quickly. The lane centreline was modelled using the Cubic Hermite spline (document 31), and a series of lane and road section modelling was performed using software adapted to the GIS database. The road network of the lane road is expressed three-dimensionally by using a B-spline curve (document 25), and the shape and accuracy of the three-dimensional road network are ensured. This type of study focuses on the geometric representation of the lane model. Tao et al, a description model of lanes of a high-precision road network is defined, and a road network is composed of lane arcs, lane attributes, intersections, intersection attributes and the like (document 23), so that the expression of the lane models in the high-precision road network is solved, but the expression of the information of the lanes in the high-precision road network is lacked, and the corresponding association relationship between the lanes and the road network is not expressed.
The content of the expression of the high-precision road network becomes finer and finer. In the united states, the Federal Highway Administration and National Highway Traffic and Safety Administration conceptually enrich detailed information on lanes of a high-precision road network, with lanes as road network contents (document 32). Further, the geometric shape and topological connection relationship of the lane are expressed, and the expression of the accuracy and content of the road network is more complete (document 4). Tao et al adds a virtual lane as content of expression at an intersection (document 24), solving the problem of lack of detailed information at the intersection. However, these studies do not provide an attribute expression of dynamic multidimensional, and have a certain limitation on the real-time property of unmanned driving.
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Disclosure of Invention
In order to solve the problems in the background and further enrich the fineness degree of a high-precision road network, only pay attention to a road section network layer and a lane network layer in the road network, and express the corresponding relation between the road section network layer and the lane network layer in the high-precision road network, the invention provides a high-precision road network model HDRNM. The model divides the HD road network into a road section network layer and a road network layer, and not only expresses the geometric, topological and attribute information of road sections and lanes in detail, but also defines the incidence relation between the road section network layer and the lane network layer. The invention defines the place where the attribute changes in the road section as the linear event point, takes the road section as the linear measurement reference, maps the linear event position in the road section to the linear event point of the lane formed in the lane through the relative position, and expresses the lane in sections at the linear event point of the lane.
The technical scheme adopted by the invention is as follows: a method for constructing a high-precision road network model is characterized by comprising the following steps:
step 1: defining a high-precision road network model;
the model is as follows:
wherein, in formula 1, W represents a road network, C is an intersection set, and R is a set of road segments; in formula 2, a road segment index set is represented by {1,2, \8230;, N }, r represents a road segment, and r represents 1 ,r 2 ,…,r N Respectively representing each road segment in the set; in equation 3, for a certain segment r, S r Is a shape point of the road section, SN r Is the starting point node of the road section, EN r Is a road section end node, Q r Is an attribute of the road section, R L Is the number of the road section connection, L S A corresponding set of lanes on the road segment; in equation 4, a set of lane indexes is represented by {1,2, \8230;, i }, where l represents a lane, and l represents a lane 1 ,l 2 ,…,l i Representing associated lanes under a certain road section; in equation 5, for a certain lane l, S l Is a shape point of a lane, SN l Is the starting node of the roadway, EN l Is a terminal node of a lane, Q l Is an attribute of the lane, L L Is the number of lane continuation; in equation 6, Q represents a dynamic attribute value, yes or no, t represents time, and Q represents an attribute value of an indication class of a lane or a link in equations 3 and 4, and this value is paired withThe corresponding value range is enumerated;
step 2: extracting road network data, including road section network layer extraction and lane network layer extraction;
and step 3: calculating the incidence relation between the road section network layer and the lane network layer;
the correlation between the road section r and the lane l corresponding to the road section in the formula 3 is:
C=f(M) (7)
in formula 7, C is the correlation corresponding to the road section and the lane, M is the set of linear event points, and the position of the attribute change on a certain road section is represented by the linear event points;
the functional relation C = f (M) of the lane corresponding to the road section is defined as:
wherein i represents a sequence of lane morphology data sets perpendicular to the lane direction; j represents a sequence of linear segments along the direction of the road segment; a totalLaneShapefunction representing a set of lane morphology data parallel to a road segment under a current road segment; totalMNum represents the total number of linear time points M on the current road section; i is n Is a unit array; l denotes a lane, l 1,j Expressing an expression in the jth linear section of the ith lane parallel to the road under the road section; LS represents an abbreviation of the lane morphology dataset LSFunction; LS (least squares) i,j An expression of a lane shape data set LSfunction parallel to the road section at the ith under the road section in the jth linear section; x is the number of j Representing the value range of coordinates in the j-1 th to j-th linear segments along the direction of the road segment; x i Representing the coordinate value range of the ith lane form data set parallel to the road section in the road direction;
and 4, step 4: and constructing a high-precision road network model.
Compared with the prior art, the invention has the beneficial effects that: an HDRNM (high definition road network model) is provided, the model divides an HD road network into a road section network layer and a road network layer, and besides the detailed expression of the geometry, topology and attribute information of the road section and the lane, the model also defines the association relationship between the road section and the lane.
The invention defines the place where the attribute changes in the road section as the linear event point, and uses the road section as the linear measurement reference, maps the linear event position in the road section to the linear event point forming the lane in the lane through the relative position, and expresses the lane in sections through the linear event point of the lane, and expresses the position of the attribute change on a certain road section through the linear event point. The mapping relation fully considers the requirement of unmanned driving, enriches the fineness degree of the high-precision road network, meets the requirement of unmanned driving on the fineness of the high-precision road network, and can be applied to automatic checking of the production result of the high-precision lane road network. The HDRNM is richer than a road network model at a road section level from data content to a data model.
Detailed Description
In order to facilitate the understanding and implementation of the present invention for those of ordinary skill in the art, the present invention is further described in detail with reference to the accompanying drawings and examples, it is to be understood that the embodiments described herein are merely illustrative and explanatory of the present invention and are not restrictive thereof.
Referring to fig. 1, the present invention provides a method for constructing a high-precision road network model, including the following steps:
step 1: defining a high-precision road network model;
the model is as follows:
wherein, in formula 1, W represents a road network, C is an intersection set, and R is a set of road segments; in formula 2, a road segment index set is represented by {1,2, \8230;, N }, r represents a road segment, and r represents 1 ,r 2 ,…,r N Respectively representing each road segment in the set; in equation 3, for a certain segment r, S r Is the shape point of the road section,SN r Is the starting point node of the road section, EN r Is a road section end point, Q r Is an attribute of a link (specific attribute, see national standard (document 34)), R L Is the number of the road section connection, L S A corresponding set of lanes on the road segment; in equation 4, a set of lane indexes is represented by {1,2, \8230;, i }, i represents a lane, and l represents a lane 1 ,l 1 ,…,l i Representing associated lanes under a certain road section; in equation 5, for a certain lane l, S l Is a shape point of a lane, SN l Is the starting node of the roadway, EN l Is a terminal node of a lane, Q l Is the attribute of the lane (including but not limited to the length of the lane, the width of the lane, the slope of the lane, the radius of curvature of the lane, etc., which may be expanded in content with the requirements of the unmanned application), L L Is the number of lane continuation; in formula 6, Q represents a dynamic attribute value, which indicates yes or no, t represents time, Q represents an attribute value of an indication class of a lane or a road segment in formulas 3 and 4, and a value range corresponding to the value is an enumeration type;
step 2: extracting road network data, including road section network layer extraction and lane network layer extraction;
extracting the road section network layer by adopting PCA Algorithm to extract the direction of the road section; principal Component Analysis (PCA) is a commonly used data analysis method (36) to describe the characteristic distribution of points. The purpose of PCA is to approximate n-dimensional raw data in k-dimension with as little loss to the data as possible after the approximation, that is, PCA finds unit vectors during the process of transforming the data from the original coordinate system to the new coordinate system so that the variance of the projection of the data in that direction can be maximized. The PCA algorithm calculates a feature matrix, which is a sample distribution that can represent most feature dimensions and is used for measuring the correlation between a point and its surrounding points. The feature vector is calculated by the feature matrix. The eigenvalues X1, X2 are obtained by calculating eigenvectors. The K = MAX { X1, X1}/{ X1+ X2} value represents the degree of linearity. Where K >0.9 represents that the clustering points are a straight line (document 33), therefore, the present embodiment determines whether the point sets in a certain point range belong to a linear relationship by the degree of linearity.
In this embodiment, a search radius searchR is first defined, and gaussian projection is performed on all coordinate points. And secondly, starting from any point, normalizing the point in the point search radius and carrying out PCA projection, and projecting the two-dimensional coordinate into a one-dimensional space. And calculating a linear degree point K value through the characteristic value. Thirdly, the embodiment screens out all point sets with K > 0.9. And merging the point sets with intersection larger than 0.9 to form a maximum linear point set, wherein the maximum linear point set respectively corresponds to a set of all lane central line points in each road section. And fourthly, carrying out PCA projection on the maximum linear point set to obtain the projection direction of the main direction of each road section, wherein the projection direction is the direction of the road section.
Lane network layer extraction, which is to establish a lane network based on multidirectional constraint; the concrete implementation process is that after the road section is extracted, the coordinate points are further classified and extracted, and different lane point sets in the road section are found. In this process, the embodiment uses the principal direction of PCA and the angle threshold σ as the constraint directions to realize lane extraction. The angle threshold σ represents a difference between the current coordinate point and a projection direction value of the next point of the coordinate point and the principal direction. From the results of the experiments, the angular threshold σ ranges between 0,30 °. An empirical value of 15 ° is generally selected as the link shape is closer to a straight line, and an angle threshold value of 30 ° is selected as the road shape is more curved.
The specific extraction process is as follows:
through the result of the last process, the point sequence sorted according to the direction and the angle of the main direction in the same road section are obtained. First, in this embodiment, each road segment is tracked according to the first point in the main direction, traversal is performed according to the principle of main direction priority, and a point in a range where an included angle between the current point and the traversal point is σ degrees is found and regarded as a point on the same lane. And repeating the loop tracking until all the points are traversed. And calculating the length of all lanes according to the direction of the road section, and finding out the linear measurement value of the linear event point on the road section.
And step 3: calculating the incidence relation between the road section network layer and the lane network layer;
the correlation between the road section r and the lane l corresponding to the road section in formula 3 is:
C=f(M) (7)
in formula 7, C is the correlation corresponding to the road section and the lane, M is the set of linear event points, and the position of the attribute change on a certain road section is represented by the linear event points;
the functional relationship C = f (M) for the lane corresponding to the road segment is defined as:
wherein i represents a sequence of lane morphology data sets perpendicular to the lane direction; j represents the sequence of linear segments along the direction of the road segment; a totalLaneShapefunction representing a set of lane morphology data parallel to a road segment under a current road segment; totalMNum represents the total number of linear time points M on the current road section; i is n Is a unit array; l denotes a lane, l 1,j Expressing an expression in a jth linear section of an ith lane parallel to the road under the road section; LS represents an abbreviation of the lane morphology dataset LSFunction; LS (least squares) i,j The expression of the ith lane form data set LSfunction parallel to the road section under the road section in the jth linear section is represented; x is the number of j Representing the value range of coordinates in the j-1 th to j-th linear segments along the direction of the road segment; x i Representing the coordinate value range of the ith lane form data set parallel to the road section in the road direction;
in the embodiment, a place where an attribute change occurs in a road section is defined as a linear event point, the road section is used as a linear measurement reference, the linear event position in the road section is mapped to a lane linear coordinate system which uses a lane as the linear measurement reference through a relative position, the linear event point of the lane is formed in the lane linear coordinate system, and then the lane is expressed in a segmented manner through the linear event point of the lane;
wherein the piecewise expression implementation process is to map the road segment to the lane by using a linear reference system; the mapping method of the linear reference system from the road section to the lane comprises the following steps: in the embodiment, a linear reference system is selected according to the road section direction, linear event points on the lanes are mapped to the corresponding lanes, the lanes are used as objects of line measurement, and linear positions corresponding to the selected lane change attributes are used as bases for dividing the lanes on the same road section. And after mapping, according to the actual condition of the Chinese road, the error between the linear event point and the original linear metric value of M in the lane direction is less than 10 meters.
And 4, step 4: and constructing a high-precision road network model.
The invention uses high precision road network model HDRNM (high definition road network model) to represent the road network model corresponding to HDmap, and the HDRNM is richer than road section level road network models from data content to data model.
It should be understood that parts of the specification not set forth in detail are well within the prior art.
It should be understood that the above description of the preferred embodiments is given for clarity and not for any purpose of limitation, and that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.