System and method for creating, storing, and updating local dynamic MAP database with safety attribute
DSRC (Dedicated short range communication) is expected to play a significant role in Transportation applications for Public Safety and Traffic Management. Some of the key applications especially safety and mobility application requires an accurate representation of the road segments. Accordingly, here, in one example, we describe a method and infrastructure for DSRC V2X (vehicle to infrastructure plus vehicle) system. This presentation, e.g., adds the following improvements on the existing technologies, as some of the examples: (a) Using Speed-Profiles for identifying Intersections/mandatory-stops/Speed-limits, etc. Also, the extension of the map coverage using speed profile data. (b) Vehicular density identification for determining confidence of generated MAP. (c) Mechanisms for identifying Lane Attributes, like Lane-Width, Lane-Connections, Possible Movement states, average travel-time on the lane, etc. In this presentation, we provide various methods and systems to manage and update such maps and its corresponding information, plus many variations on those.
1. A method for creating, storing, and updating local dynamic map database with safety attribute, for a street or highway, said method comprising:
a central computer obtaining basic safety messages in an intended region of map, wherein the basic safety messages include vehicle data;
filtering out a first basic safety message data out of said basic safety messages which falls outside of said intended region of map;
adaptively defining said intended region of map, using speed profiles data in each road segment of interest;
wherein a high average speed road segment requires greater map coverage than a low average speed road segment;
receiving path history or trajectory from an at least one vehicle;
checking accuracy of said path history or trajectory;
when said accuracy of said path history or trajectory is better than a first accuracy threshold distance, storing said path history or trajectory, instead of actual locations reported by said at least one vehicle;
when said accuracy of said path history or trajectory is worse than said first accuracy threshold distance, storing said actual locations reported by said at least one vehicle;
storing a location, heading, speed, and timestamp of each of said basic safety messages received; and
when corresponding number of vehicles for stored data is above a first number of vehicle threshold, then starting generation of a temporary map;
said central computer further:
generating lanes, wherein generating lanes includes:
assigning equal weights for all paths at beginning, as an initialization step;
combining paths or parts of paths which have a separation distance of smaller than a threshold fraction of a lane width, to produce a resultant path, to indicate that said paths or parts of paths are actually the same;
wherein weight of said resultant path is calculated using the equation:
(1/sqrt(((1/w1) 2 *(1/w2) 2 )/((1/w1) 2 +(1/w2) 2 )))
wherein sqrt is the square root function, w1 is weight of a first path, and w2 is weight of a second path;
combining paths which start and end with same heading angles;
combining parts of paths of vehicles which have same headings in said parts;
updating weights of the paths or parts of the paths of combined paths which are headed in same direction, using the equation:
(1/sqrt(((1/w1) 2 *(1/w2) 2 )/((1/w1) 2 +(1/w2) 2 )))
detecting lane changes in captured data, wherein detecting lane changes includes using statistical median operation to filter outliers in positions and paths for lane change detection;
determining an intersection region and splitting lanes wherein determining an intersection region and splitting lanes includes:
identifying an intersection diamond region using speed profiles of vehicles, heading angles of said vehicles, and intersection of lanes, generated from said vehicles' travel paths;
obtaining intersection of lanes, generated from said vehicles' travel paths;
constructing intersection points of lanes for each of lanes which differ in heading angle by more than a threshold angle value;
constructing a convex polygon using said intersection points of lanes;
expanding a convex polygon by adding a certain amount of width, equal to a specific fraction of lane width on each of sides;
splitting lanes, based on intersection region polygon;
determining lane type as ingress or egress, wherein determining lane type includes determining a difference in angle between vehicle heading and lane heading;
combining incoming and outgoing lanes which fall on one side of said polygon and have either same or exactly opposite heading angle, with difference of approximately 180 degrees;
determining connected lanes;
determining movement states for each of said ingress lanes
based on connected egress lane's maneuver code,
wherein connection maneuvers comprise: left-turn, straight, or right-turn;
updating said map data;
generating lanes for said street or highway.
2. The method for creating, storing, and updating local dynamic map database with safety attribute, for a street or highway, as recited in claim 1 , said method further comprises:
identifying an idle vehicle, impeding traffic situation, or accident in said street or highway.
3. The method for creating, storing, and updating local dynamic map database with safety attribute, for a street or highway, as recited in claim 1 , said method further comprises:
using a short range communication device with a road-side equipment in infrastructure and an on-board unit in a first vehicle.
4. The method for creating, storing, and updating local dynamic map database with safety attribute, for a street or highway, as recited in claim 1 , said method further comprises:
storing a time-stamp for a basic safety message.